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  • Cannot determine ethernet address for proxy ARP on PPTP

    - by Linux Intel
    I installed pptp server on a centos 6 64bit server PPTP Server ip : 55.66.77.10 PPTP Local ip : 10.0.0.1 Client1 IP : 10.0.0.60 centos 5 64bit Client2 IP : 10.0.0.61 centos5 64bit PPTP Server can ping Client1 And client 1 can ping PPTP Server PPTP Server can ping Client2 And client 2 can ping PPTP Server The problem is client 1 can not ping Client 2 and i get this error also on PPTP server error log Cannot determine ethernet address for proxy ARP Ping from Client2 to Client1 PING 10.0.0.60 (10.0.0.60) 56(84) bytes of data. --- 10.0.0.60 ping statistics --- 6 packets transmitted, 0 received, 100% packet loss, time 5000ms route -n on PPTP Server Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.0.60 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 10.0.0.61 0.0.0.0 255.255.255.255 UH 0 0 0 ppp1 55.66.77.10 0.0.0.0 255.255.255.248 U 0 0 0 eth0 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth0 0.0.0.0 55.66.77.19 0.0.0.0 UG 0 0 0 eth0 route -n On Client 1 Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 55.66.77.10 70.14.13.19 255.255.255.255 UGH 0 0 0 eth0 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth1 0.0.0.0 70.14.13.19 0.0.0.0 UG 0 0 0 eth0 route -n On Client 2 Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 55.66.77.10 84.56.120.60 255.255.255.255 UGH 0 0 0 eth1 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth0 0.0.0.0 84.56.120.60 0.0.0.0 UG 0 0 0 eth1 cat /etc/ppp/options.pptpd on PPTP server ############################################################################### # $Id: options.pptpd,v 1.11 2005/12/29 01:21:09 quozl Exp $ # # Sample Poptop PPP options file /etc/ppp/options.pptpd # Options used by PPP when a connection arrives from a client. # This file is pointed to by /etc/pptpd.conf option keyword. # Changes are effective on the next connection. See "man pppd". # # You are expected to change this file to suit your system. As # packaged, it requires PPP 2.4.2 and the kernel MPPE module. ############################################################################### # Authentication # Name of the local system for authentication purposes # (must match the second field in /etc/ppp/chap-secrets entries) name pptpd # Strip the domain prefix from the username before authentication. # (applies if you use pppd with chapms-strip-domain patch) #chapms-strip-domain # Encryption # (There have been multiple versions of PPP with encryption support, # choose with of the following sections you will use.) # BSD licensed ppp-2.4.2 upstream with MPPE only, kernel module ppp_mppe.o # {{{ refuse-pap refuse-chap refuse-mschap # Require the peer to authenticate itself using MS-CHAPv2 [Microsoft # Challenge Handshake Authentication Protocol, Version 2] authentication. require-mschap-v2 # Require MPPE 128-bit encryption # (note that MPPE requires the use of MSCHAP-V2 during authentication) require-mppe-128 # }}} # OpenSSL licensed ppp-2.4.1 fork with MPPE only, kernel module mppe.o # {{{ #-chap #-chapms # Require the peer to authenticate itself using MS-CHAPv2 [Microsoft # Challenge Handshake Authentication Protocol, Version 2] authentication. #+chapms-v2 # Require MPPE encryption # (note that MPPE requires the use of MSCHAP-V2 during authentication) #mppe-40 # enable either 40-bit or 128-bit, not both #mppe-128 #mppe-stateless # }}} # Network and Routing # If pppd is acting as a server for Microsoft Windows clients, this # option allows pppd to supply one or two DNS (Domain Name Server) # addresses to the clients. The first instance of this option # specifies the primary DNS address; the second instance (if given) # specifies the secondary DNS address. #ms-dns 10.0.0.1 #ms-dns 10.0.0.2 # If pppd is acting as a server for Microsoft Windows or "Samba" # clients, this option allows pppd to supply one or two WINS (Windows # Internet Name Services) server addresses to the clients. The first # instance of this option specifies the primary WINS address; the # second instance (if given) specifies the secondary WINS address. #ms-wins 10.0.0.3 #ms-wins 10.0.0.4 # Add an entry to this system's ARP [Address Resolution Protocol] # table with the IP address of the peer and the Ethernet address of this # system. This will have the effect of making the peer appear to other # systems to be on the local ethernet. # (you do not need this if your PPTP server is responsible for routing # packets to the clients -- James Cameron) proxyarp # Normally pptpd passes the IP address to pppd, but if pptpd has been # given the delegate option in pptpd.conf or the --delegate command line # option, then pppd will use chap-secrets or radius to allocate the # client IP address. The default local IP address used at the server # end is often the same as the address of the server. To override this, # specify the local IP address here. # (you must not use this unless you have used the delegate option) #10.8.0.100 # Logging # Enable connection debugging facilities. # (see your syslog configuration for where pppd sends to) debug # Print out all the option values which have been set. # (often requested by mailing list to verify options) #dump # Miscellaneous # Create a UUCP-style lock file for the pseudo-tty to ensure exclusive # access. lock # Disable BSD-Compress compression nobsdcomp # Disable Van Jacobson compression # (needed on some networks with Windows 9x/ME/XP clients, see posting to # poptop-server on 14th April 2005 by Pawel Pokrywka and followups, # http://marc.theaimsgroup.com/?t=111343175400006&r=1&w=2 ) novj novjccomp # turn off logging to stderr, since this may be redirected to pptpd, # which may trigger a loopback nologfd # put plugins here # (putting them higher up may cause them to sent messages to the pty) cat /etc/ppp/options.pptp on Client1 and Client2 ############################################################################### # $Id: options.pptp,v 1.3 2006/03/26 23:11:05 quozl Exp $ # # Sample PPTP PPP options file /etc/ppp/options.pptp # Options used by PPP when a connection is made by a PPTP client. # This file can be referred to by an /etc/ppp/peers file for the tunnel. # Changes are effective on the next connection. See "man pppd". # # You are expected to change this file to suit your system. As # packaged, it requires PPP 2.4.2 or later from http://ppp.samba.org/ # and the kernel MPPE module available from the CVS repository also on # http://ppp.samba.org/, which is packaged for DKMS as kernel_ppp_mppe. ############################################################################### # Lock the port lock # Authentication # We don't need the tunnel server to authenticate itself noauth # We won't do PAP, EAP, CHAP, or MSCHAP, but we will accept MSCHAP-V2 # (you may need to remove these refusals if the server is not using MPPE) refuse-pap refuse-eap refuse-chap refuse-mschap # Compression # Turn off compression protocols we know won't be used nobsdcomp nodeflate # Encryption # (There have been multiple versions of PPP with encryption support, # choose which of the following sections you will use. Note that MPPE # requires the use of MSCHAP-V2 during authentication) # # Note that using PPTP with MPPE and MSCHAP-V2 should be considered # insecure: # http://marc.info/?l=pptpclient-devel&m=134372640219039&w=2 # https://github.com/moxie0/chapcrack/blob/master/README.md # http://technet.microsoft.com/en-us/security/advisory/2743314 # http://ppp.samba.org/ the PPP project version of PPP by Paul Mackarras # ppp-2.4.2 or later with MPPE only, kernel module ppp_mppe.o # If the kernel is booted in FIPS mode (fips=1), the ppp_mppe.ko module # is not allowed and PPTP-MPPE is not available. # {{{ # Require MPPE 128-bit encryption #require-mppe-128 # }}} # http://mppe-mppc.alphacron.de/ fork from PPP project by Jan Dubiec # ppp-2.4.2 or later with MPPE and MPPC, kernel module ppp_mppe_mppc.o # {{{ # Require MPPE 128-bit encryption #mppe required,stateless # }}} IPtables is stopped on clients and server, Also net.ipv4.ip_forward = 1 is enabled on PPTP Server. How can i solve this problem .?

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  • mysql: Bind on unix socket: Permission denied

    - by Alex
    Can't start mysql with: sudo /usr/bin/mysqld_safe --datadir=/srv/mysql/myDB --log-error=/srv/mysql/logs/mysqld-myDB.log --pid-file=/srv/mysql/pids/mysqld-myDB.pid --user=mysql --socket=/srv/mysql/sockets/mysql-myDB.sock --port=3700 120222 13:40:48 mysqld_safe Starting mysqld daemon with databases from /srv/mysql/myDB 120222 13:40:54 mysqld_safe mysqld from pid file /srv/mysql/pids/mysqld-myDB.pid ended /srv/mysql/logs/mysqld-myDB.log: 120222 13:43:53 mysqld_safe Starting mysqld daemon with databases from /srv/mysql/myDB 120222 13:43:53 [Note] Plugin 'FEDERATED' is disabled. /usr/sbin/mysqld: Table 'plugin' is read only 120222 13:43:53 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it. 120222 13:43:53 InnoDB: Completed initialization of buffer pool 120222 13:43:53 InnoDB: Started; log sequence number 32 4232720908 120222 13:43:53 [ERROR] Can't start server : Bind on unix socket: Permission denied 120222 13:43:53 [ERROR] Do you already have another mysqld server running on socket: /srv/mysql/sockets/mysql-myDB.sock ? 120222 13:43:53 [ERROR] Aborting 120222 13:43:53 InnoDB: Starting shutdown... One instance mysqld is running: $ ps aux | grep mysql mysql 1093 0.0 0.2 169972 18700 ? Ssl 11:50 0:02 /usr/sbin/mysqld $ Port 3700 is available: $ netstat -a | grep 3700 $ Directory with sockets is empty: $ ls /srv/mysql/sockets/ $ There are all permissions: $ ls -l /srv/mysql/ total 20 drwxrwxrwx 2 mysql mysql 4096 2012-02-22 13:28 logs drwxrwxrwx 13 mysql mysql 4096 2012-02-22 13:44 myDB drwxrwxrwx 2 mysql mysql 4096 2012-02-22 12:55 pids drwxrwxrwx 2 mysql mysql 4096 2012-02-22 12:55 sockets drwxrwxrwx 2 mysql mysql 4096 2012-02-22 13:25 version Apparmor config: $cat /etc/apparmor.d/usr.sbin.mysqld # vim:syntax=apparmor # Last Modified: Tue Jun 19 17:37:30 2007 #include <tunables/global> /usr/sbin/mysqld flags=(complain) { #include <abstractions/base> #include <abstractions/nameservice> #include <abstractions/user-tmp> #include <abstractions/mysql> #include <abstractions/winbind> capability dac_override, capability sys_resource, capability setgid, capability setuid, network tcp, /etc/hosts.allow r, /etc/hosts.deny r, /etc/mysql/*.pem r, /etc/mysql/conf.d/ r, /etc/mysql/conf.d/* r, /etc/mysql/*.cnf r, /usr/lib/mysql/plugin/ r, /usr/lib/mysql/plugin/*.so* mr, /usr/sbin/mysqld mr, /usr/share/mysql/** r, /var/log/mysql.log rw, /var/log/mysql.err rw, /var/lib/mysql/ r, /var/lib/mysql/** rwk, /var/log/mysql/ r, /var/log/mysql/* rw, /{,var/}run/mysqld/mysqld.pid w, /{,var/}run/mysqld/mysqld.sock w, /srv/mysql/ r, /srv/mysql/** rwk, /sys/devices/system/cpu/ r, # Site-specific additions and overrides. See local/README for details. #include <local/usr.sbin.mysqld> } Any suggestions? UPD1: $ touch /srv/mysql/sockets/mysql-myDB.sock $ sudo chown mysql:mysql /srv/mysql/sockets/mysql-myDB.sock $ ls -l /srv/mysql/sockets/mysql-myDB.sock -rw-rw-r-- 1 mysql mysql 0 2012-02-22 14:29 /srv/mysql/sockets/mysql-myDB.sock $ sudo /usr/bin/mysqld_safe --datadir=/srv/mysql/myDB --log-error=/srv/mysql/logs/mysqld-myDB.log --pid-file=/srv/mysql/pids/mysqld-myDB.pid --user=mysql --socket=/srv/mysql/sockets/mysql-myDB.sock --port=3700 120222 14:30:18 mysqld_safe Can't log to error log and syslog at the same time. Remove all --log-error configuration options for --syslog to take effect. 120222 14:30:18 mysqld_safe Logging to '/srv/mysql/logs/mysqld-myDB.log'. 120222 14:30:18 mysqld_safe Starting mysqld daemon with databases from /srv/mysqlmyDB 120222 14:30:24 mysqld_safe mysqld from pid file /srv/mysql/pids/mysqld-myDB.pid ended $ ls -l /srv/mysql/sockets/mysql-myDB.sock ls: cannot access /srv/mysql/sockets/mysql-myDB.sock: No such file or directory $ UPD2: $ sudo netstat -lnp | grep mysql tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 1093/mysqld unix 2 [ ACC ] STREAM LISTENING 5912 1093/mysqld /var/run/mysqld/mysqld.sock $ sudo lsof | grep /srv/mysql/sockets/mysql-myDB.sock lsof: WARNING: can't stat() fuse.gvfs-fuse-daemon file system /home/sears/.gvfs Output information may be incomplete. UPD3: $ cat /etc/mysql/my.cnf # # The MySQL database server configuration file. # # You can copy this to one of: # - "/etc/mysql/my.cnf" to set global options, # - "~/.my.cnf" to set user-specific options. # # One can use all long options that the program supports. # Run program with --help to get a list of available options and with # --print-defaults to see which it would actually understand and use. # # For explanations see # http://dev.mysql.com/doc/mysql/en/server-system-variables.html # This will be passed to all mysql clients # It has been reported that passwords should be enclosed with ticks/quotes # escpecially if they contain "#" chars... # Remember to edit /etc/mysql/debian.cnf when changing the socket location. [client] port = 3306 socket = /var/run/mysqld/mysqld.sock # Here is entries for some specific programs # The following values assume you have at least 32M ram # This was formally known as [safe_mysqld]. Both versions are currently parsed. [mysqld_safe] socket = /var/run/mysqld/mysqld.sock nice = 0 [mysqld] # # * Basic Settings # # # * IMPORTANT # If you make changes to these settings and your system uses apparmor, you may # also need to also adjust /etc/apparmor.d/usr.sbin.mysqld. # user = mysql socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp skip-external-locking # # Instead of skip-networking the default is now to listen only on # localhost which is more compatible and is not less secure. #bind-address = 127.0.0.1 # # * Fine Tuning # key_buffer = 16M max_allowed_packet = 16M thread_stack = 192K thread_cache_size = 8 # This replaces the startup script and checks MyISAM tables if needed # the first time they are touched myisam-recover = BACKUP #max_connections = 100 #table_cache = 64 #thread_concurrency = 10 # # * Query Cache Configuration # query_cache_limit = 1M query_cache_size = 16M # # * Logging and Replication # # Both location gets rotated by the cronjob. # Be aware that this log type is a performance killer. # As of 5.1 you can enable the log at runtime! #general_log_file = /var/log/mysql/mysql.log #general_log = 1 log_error = /var/log/mysql/error.log # Here you can see queries with especially long duration #log_slow_queries = /var/log/mysql/mysql-slow.log #long_query_time = 2 #log-queries-not-using-indexes # # The following can be used as easy to replay backup logs or for replication. # note: if you are setting up a replication slave, see README.Debian about # other settings you may need to change. #server-id = 1 #log_bin = /var/log/mysql/mysql-bin.log expire_logs_days = 10 max_binlog_size = 100M #binlog_do_db = include_database_name #binlog_ignore_db = include_database_name # # * InnoDB # # InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/. # Read the manual for more InnoDB related options. There are many! # # * Security Features # # Read the manual, too, if you want chroot! # chroot = /var/lib/mysql/ # # For generating SSL certificates I recommend the OpenSSL GUI "tinyca". # # ssl-ca=/etc/mysql/cacert.pem # ssl-cert=/etc/mysql/server-cert.pem # ssl-key=/etc/mysql/server-key.pem [mysqldump] quick quote-names max_allowed_packet = 16M [mysql] #no-auto-rehash # faster start of mysql but no tab completition [isamchk] key_buffer = 16M # # * IMPORTANT: Additional settings that can override those from this file! # The files must end with '.cnf', otherwise they'll be ignored. # !includedir /etc/mysql/conf.d/

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  • Why doesn't pppd over ssh work here? Why can't I kill pppd?

    - by Peter V. Mørch
    I'm trying to setup a simple ppp tunnel over ssh. It works on several machines just fine. But on one machine, pppd gets "stuck": > pgrep pppd | xargs ps up USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 4178 0.0 0.1 3020 1088 pts/1 Ds+ 05:28 0:00 /usr/sbin/pppd Any attempt to kill it (even sudo kill -9 4178) has no effect that I can see. strace -p 4178 also hangs similarly. After it has been started for a while, I start getting messages in dmesg like shown below. It is started like so from another machine: ssh -t root@server /usr/sbin/pppd passive noauth When I do this to one of the machines that work, the remote end's pppd spits out garbage/binary data to the console (as expected). When I do it to the one that fails, I get no output from pppd, but the ssh session eventually times out. If I instead ssh to the machine, and then run /usr/sbin/pppd passive noauth in a separate step I also get the expected binary output. I now have a couple of questions: What could be up with the one machine where pppd fails? I don't even know where to start looking... What could be the difference between ssh -t root@server /usr/sbin/pppd passive noauth in a single step and ssh root@server and /usr/sbin/pppd passive noauth in two steps? How can it be that I can't kill the process even with sudo kill -9? The only way I know is to reboot. (I've tried searching for something similar but didn't get anywhere so I'm sorry I don't have any more leads) Any ideas? The problem machine runs in debian on VMware "hardware" (as do the ones that work) and it exhibits the problem when cloned and on both debian lenny (original) and squeeze (after upgrade) dmesg entries: [ 1198.727248] INFO: task pppd:4178 blocked for more than 120 seconds. [ 1198.727507] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 1198.727904] pppd D ece2dc9c 0 4178 4174 0x00000004 [ 1198.727908] 00000098 00000082 f2503520 ece2dc9c 0000b1e7 00000000 c148d1c0 c148d1c0 [ 1198.727913] f2a06100 f6e071c0 00000000 ece2dc18 f5cd07e0 00000000 ece2d400 ece2dc9d [ 1198.727918] 00c52300 ece2dcbc f67bfef8 ec98e480 f291cec0 00000000 c10cf5b0 c10dfd21 [ 1198.727923] Call Trace: [ 1198.727926] [<c10cf5b0>] ? nameidata_to_filp+0x37/0x41 [ 1198.727929] [<c10dfd21>] ? dput+0x21/0xb7 [ 1198.727932] [<c11cfecc>] ? tty_ldisc_ref_wait+0x5f/0x76 [ 1198.727935] [<c104de7a>] ? wake_up_bit+0x5c/0x5c [ 1198.727938] [<c11cb91b>] ? tty_ioctl+0x85f/0x8ba [ 1198.727941] [<c10fec18>] ? do_lock_file_wait+0x3d/0xd9 [ 1198.727944] [<c1162c97>] ? _copy_from_user+0x2b/0x102 [ 1198.727946] [<c11cb0bc>] ? tty_check_change+0xb9/0xb9 [ 1198.727949] [<c10dbeb7>] ? do_vfs_ioctl+0x485/0x4c7 [ 1198.727952] [<c10db59a>] ? do_fcntl+0x24f/0x3a2 [ 1198.727954] [<c10dbf3a>] ? sys_ioctl+0x41/0x58 [ 1198.727957] [<c12c6a1f>] ? sysenter_do_call+0x12/0x28 [ 1318.457225] INFO: task sshd:4174 blocked for more than 120 seconds. [ 1318.457500] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 1318.457896] sshd D f25024cc 0 4174 2393 0x00000000 [ 1318.457901] 00000098 00000086 f2a06940 f25024cc 0000b246 00000000 c148d1c0 c148d1c0 [ 1318.457906] f2503520 f6e071c0 00000000 3f056585 0000000f ece2d4bc 3f056585 f2503520 [ 1318.457911] ec98bb38 ec98bbdc 00000000 00000000 00000000 c12c09b5 f2503520 c10327cb [ 1318.457916] Call Trace: [ 1318.457926] [<c12c09b5>] ? schedule_hrtimeout_range_clock+0x3c/0xd9 [ 1318.457931] [<c10327cb>] ? try_to_wake_up+0x13f/0x13f [ 1318.457935] [<c11cfecc>] ? tty_ldisc_ref_wait+0x5f/0x76 [ 1318.457940] [<c104de7a>] ? wake_up_bit+0x5c/0x5c [ 1318.457943] [<c11c9ad3>] ? tty_poll+0x32/0x5e [ 1318.457947] [<c10dd4d5>] ? do_select+0x2a1/0x42e [ 1318.457950] [<c10dcb83>] ? poll_freewait+0x69/0x69 [ 1318.457953] [<c10dcc25>] ? __pollwait+0xa2/0xa2 [ 1318.457955] [<c10dcc25>] ? __pollwait+0xa2/0xa2 [ 1318.457958] [<c10dcc25>] ? __pollwait+0xa2/0xa2 [ 1318.457960] [<c10dcc25>] ? __pollwait+0xa2/0xa2 [ 1318.457963] [<c10dcc25>] ? __pollwait+0xa2/0xa2 [ 1318.457965] [<c10dcc25>] ? __pollwait+0xa2/0xa2 [ 1318.457968] [<c10dcc25>] ? __pollwait+0xa2/0xa2 [ 1318.457971] [<c10429c2>] ? lock_timer_base+0x19/0x35 [ 1318.457974] [<c1042eb5>] ? __mod_timer+0x10c/0x116 [ 1318.457977] [<c1042f89>] ? mod_timer+0x69/0x6e [ 1318.457981] [<c121325d>] ? sk_reset_timer+0xc/0x16 [ 1318.457984] [<c1252f57>] ? tcp_event_new_data_sent+0x66/0x6b [ 1318.457987] [<c1255b85>] ? tcp_write_xmit+0x7a7/0x86a [ 1318.457990] [<c121760d>] ? __alloc_skb+0x50/0xfd [ 1318.457994] [<c12c12bc>] ? _raw_spin_lock_bh+0x8/0x1e [ 1318.457996] [<c1212e98>] ? release_sock+0x10/0xc4 [ 1318.457999] [<c124b543>] ? tcp_sendmsg+0x6dd/0x7b7 [ 1318.458003] [<c1162c97>] ? _copy_from_user+0x2b/0x102 [ 1318.458006] [<c10dd7a0>] ? core_sys_select+0x13e/0x1c3 [ 1318.458009] [<c12102a3>] ? sock_aio_write+0xc0/0xd4 [ 1318.458012] [<c10d0655>] ? do_sync_write+0xa0/0xe4 [ 1318.458016] [<c10b141c>] ? handle_mm_fault+0x222/0x238 [ 1318.458019] [<c10f6096>] ? fsnotify+0x1de/0x1f9 [ 1318.458022] [<c10dd9e8>] ? sys_select+0x6e/0x8f [ 1318.458024] [<c10d105e>] ? sys_write+0x3c/0x63 [ 1318.458028] [<c12c6a1f>] ? sysenter_do_call+0x12/0x28

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  • Configuring OpenLDAP and SSL

    - by Stormshadow
    I am having trouble trying to connect to a secure OpenLDAP server which I have set up. On running my LDAP client code java -Djavax.net.debug=ssl LDAPConnector I get the following exception trace (java version 1.6.0_17) trigger seeding of SecureRandom done seeding SecureRandom %% No cached client session *** ClientHello, TLSv1 RandomCookie: GMT: 1256110124 bytes = { 224, 19, 193, 148, 45, 205, 108, 37, 101, 247, 112, 24, 157, 39, 111, 177, 43, 53, 206, 224, 68, 165, 55, 185, 54, 203, 43, 91 } Session ID: {} Cipher Suites: [SSL_RSA_WITH_RC4_128_MD5, SSL_RSA_WITH_RC4_128_SHA, TLS_RSA_WITH_AES_128_CBC_SHA, TLS_DHE_RSA_WITH_AES_128_CBC_SHA, TLS_DHE_DSS_WITH_AES_128_CBC_SHA, SSL_RSA_W ITH_3DES_EDE_CBC_SHA, SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA, SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA, SSL_RSA_WITH_DES_CBC_SHA, SSL_DHE_RSA_WITH_DES_CBC_SHA, SSL_DHE_DSS_WITH_DES_CBC_SH A, SSL_RSA_EXPORT_WITH_RC4_40_MD5, SSL_RSA_EXPORT_WITH_DES40_CBC_SHA, SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA, SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA] Compression Methods: { 0 } *** Thread-0, WRITE: TLSv1 Handshake, length = 73 Thread-0, WRITE: SSLv2 client hello message, length = 98 Thread-0, received EOFException: error Thread-0, handling exception: javax.net.ssl.SSLHandshakeException: Remote host closed connection during handshake Thread-0, SEND TLSv1 ALERT: fatal, description = handshake_failure Thread-0, WRITE: TLSv1 Alert, length = 2 Thread-0, called closeSocket() main, handling exception: javax.net.ssl.SSLHandshakeException: Remote host closed connection during handshake javax.naming.CommunicationException: simple bind failed: ldap.natraj.com:636 [Root exception is javax.net.ssl.SSLHandshakeException: Remote host closed connection during hands hake] at com.sun.jndi.ldap.LdapClient.authenticate(Unknown Source) at com.sun.jndi.ldap.LdapCtx.connect(Unknown Source) at com.sun.jndi.ldap.LdapCtx.<init>(Unknown Source) at com.sun.jndi.ldap.LdapCtxFactory.getUsingURL(Unknown Source) at com.sun.jndi.ldap.LdapCtxFactory.getUsingURLs(Unknown Source) at com.sun.jndi.ldap.LdapCtxFactory.getLdapCtxInstance(Unknown Source) at com.sun.jndi.ldap.LdapCtxFactory.getInitialContext(Unknown Source) at javax.naming.spi.NamingManager.getInitialContext(Unknown Source) at javax.naming.InitialContext.getDefaultInitCtx(Unknown Source) at javax.naming.InitialContext.init(Unknown Source) at javax.naming.InitialContext.<init>(Unknown Source) at javax.naming.directory.InitialDirContext.<init>(Unknown Source) at LDAPConnector.CallSecureLDAPServer(LDAPConnector.java:43) at LDAPConnector.main(LDAPConnector.java:237) Caused by: javax.net.ssl.SSLHandshakeException: Remote host closed connection during handshake at com.sun.net.ssl.internal.ssl.SSLSocketImpl.readRecord(Unknown Source) at com.sun.net.ssl.internal.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source) at com.sun.net.ssl.internal.ssl.SSLSocketImpl.readDataRecord(Unknown Source) at com.sun.net.ssl.internal.ssl.AppInputStream.read(Unknown Source) at java.io.BufferedInputStream.fill(Unknown Source) at java.io.BufferedInputStream.read1(Unknown Source) at java.io.BufferedInputStream.read(Unknown Source) at com.sun.jndi.ldap.Connection.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Caused by: java.io.EOFException: SSL peer shut down incorrectly at com.sun.net.ssl.internal.ssl.InputRecord.read(Unknown Source) ... 9 more I am able to connect to the same secure LDAP server however if I use another version of java (1.6.0_14) I have created and installed the server certificates in the cacerts of both the JRE's as mentioned in this guide -- OpenLDAP with SSL When I run ldapsearch -x on the server I get # extended LDIF # # LDAPv3 # base <dc=localdomain> (default) with scope subtree # filter: (objectclass=*) # requesting: ALL # # localdomain dn: dc=localdomain objectClass: top objectClass: dcObject objectClass: organization o: localdomain dc: localdomain # admin, localdomain dn: cn=admin,dc=localdomain objectClass: simpleSecurityObject objectClass: organizationalRole cn: admin description: LDAP administrator # search result search: 2 result: 0 Success # numResponses: 3 # numEntries: 2 On running openssl s_client -connect ldap.natraj.com:636 -showcerts , I obtain the self signed certificate. My slapd.conf file is as follows ####################################################################### # Global Directives: # Features to permit #allow bind_v2 # Schema and objectClass definitions include /etc/ldap/schema/core.schema include /etc/ldap/schema/cosine.schema include /etc/ldap/schema/nis.schema include /etc/ldap/schema/inetorgperson.schema # Where the pid file is put. The init.d script # will not stop the server if you change this. pidfile /var/run/slapd/slapd.pid # List of arguments that were passed to the server argsfile /var/run/slapd/slapd.args # Read slapd.conf(5) for possible values loglevel none # Where the dynamically loaded modules are stored modulepath /usr/lib/ldap moduleload back_hdb # The maximum number of entries that is returned for a search operation sizelimit 500 # The tool-threads parameter sets the actual amount of cpu's that is used # for indexing. tool-threads 1 ####################################################################### # Specific Backend Directives for hdb: # Backend specific directives apply to this backend until another # 'backend' directive occurs backend hdb ####################################################################### # Specific Backend Directives for 'other': # Backend specific directives apply to this backend until another # 'backend' directive occurs #backend <other> ####################################################################### # Specific Directives for database #1, of type hdb: # Database specific directives apply to this databasse until another # 'database' directive occurs database hdb # The base of your directory in database #1 suffix "dc=localdomain" # rootdn directive for specifying a superuser on the database. This is needed # for syncrepl. rootdn "cn=admin,dc=localdomain" # Where the database file are physically stored for database #1 directory "/var/lib/ldap" # The dbconfig settings are used to generate a DB_CONFIG file the first # time slapd starts. They do NOT override existing an existing DB_CONFIG # file. You should therefore change these settings in DB_CONFIG directly # or remove DB_CONFIG and restart slapd for changes to take effect. # For the Debian package we use 2MB as default but be sure to update this # value if you have plenty of RAM dbconfig set_cachesize 0 2097152 0 # Sven Hartge reported that he had to set this value incredibly high # to get slapd running at all. See http://bugs.debian.org/303057 for more # information. # Number of objects that can be locked at the same time. dbconfig set_lk_max_objects 1500 # Number of locks (both requested and granted) dbconfig set_lk_max_locks 1500 # Number of lockers dbconfig set_lk_max_lockers 1500 # Indexing options for database #1 index objectClass eq # Save the time that the entry gets modified, for database #1 lastmod on # Checkpoint the BerkeleyDB database periodically in case of system # failure and to speed slapd shutdown. checkpoint 512 30 # Where to store the replica logs for database #1 # replogfile /var/lib/ldap/replog # The userPassword by default can be changed # by the entry owning it if they are authenticated. # Others should not be able to see it, except the # admin entry below # These access lines apply to database #1 only access to attrs=userPassword,shadowLastChange by dn="cn=admin,dc=localdomain" write by anonymous auth by self write by * none # Ensure read access to the base for things like # supportedSASLMechanisms. Without this you may # have problems with SASL not knowing what # mechanisms are available and the like. # Note that this is covered by the 'access to *' # ACL below too but if you change that as people # are wont to do you'll still need this if you # want SASL (and possible other things) to work # happily. access to dn.base="" by * read # The admin dn has full write access, everyone else # can read everything. access to * by dn="cn=admin,dc=localdomain" write by * read # For Netscape Roaming support, each user gets a roaming # profile for which they have write access to #access to dn=".*,ou=Roaming,o=morsnet" # by dn="cn=admin,dc=localdomain" write # by dnattr=owner write ####################################################################### # Specific Directives for database #2, of type 'other' (can be hdb too): # Database specific directives apply to this databasse until another # 'database' directive occurs #database <other> # The base of your directory for database #2 #suffix "dc=debian,dc=org" ####################################################################### # SSL: # Uncomment the following lines to enable SSL and use the default # snakeoil certificates. #TLSCertificateFile /etc/ssl/certs/ssl-cert-snakeoil.pem #TLSCertificateKeyFile /etc/ssl/private/ssl-cert-snakeoil.key TLSCipherSuite TLS_RSA_AES_256_CBC_SHA TLSCACertificateFile /etc/ldap/ssl/server.pem TLSCertificateFile /etc/ldap/ssl/server.pem TLSCertificateKeyFile /etc/ldap/ssl/server.pem My ldap.conf file is # # LDAP Defaults # # See ldap.conf(5) for details # This file should be world readable but not world writable. HOST ldap.natraj.com PORT 636 BASE dc=localdomain URI ldaps://ldap.natraj.com TLS_CACERT /etc/ldap/ssl/server.pem TLS_REQCERT allow #SIZELIMIT 12 #TIMELIMIT 15 #DEREF never Why is it that I can connect to the same server using one version of JRE while I cannot with another ?

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  • Trouble connecting to vsftpd on ubuntu server

    - by littleK
    I have installed Ubuntu Server 10.10 and I am using it to host a domain that I have. I am trying to set up FTP for the server, but I am running into some problems. I have successfully installed vsFTPd and I have opened up ports 20, 21 on my firewall. In my vsFTPd configuration, I have enabled SSL. Every time I try to connect to my server via FTP, I receive a "Connection Refused" error. I have had a little more success with SSL disabled, however the connection process will time out after the LIST command (but it does accept my authentication). Here is my vsFTPd configuration, the SSL stuff is at the bottom: # Example config file /etc/vsftpd.conf # # The default compiled in settings are fairly paranoid. This sample file # loosens things up a bit, to make the ftp daemon more usable. # Please see vsftpd.conf.5 for all compiled in defaults. # # READ THIS: This example file is NOT an exhaustive list of vsftpd options. # Please read the vsftpd.conf.5 manual page to get a full idea of vsftpd's # capabilities. # # # Run standalone? vsftpd can run either from an inetd or as a standalone # daemon started from an initscript. listen=YES # # Run standalone with IPv6? # Like the listen parameter, except vsftpd will listen on an IPv6 socket # instead of an IPv4 one. This parameter and the listen parameter are mutually # exclusive. #listen_ipv6=YES # # Allow anonymous FTP? (Disabled by default) anonymous_enable=NO # # Uncomment this to allow local users to log in. local_enable=YES # # Uncomment this to enable any form of FTP write command. write_enable=YES # # Default umask for local users is 077. You may wish to change this to 022, # if your users expect that (022 is used by most other ftpd's) #local_umask=022 # # Uncomment this to allow the anonymous FTP user to upload files. This only # has an effect if the above global write enable is activated. Also, you will # obviously need to create a directory writable by the FTP user. #anon_upload_enable=YES # # Uncomment this if you want the anonymous FTP user to be able to create # new directories. #anon_mkdir_write_enable=YES # # Activate directory messages - messages given to remote users when they # go into a certain directory. dirmessage_enable=YES # # If enabled, vsftpd will display directory listings with the time # in your local time zone. The default is to display GMT. The # times returned by the MDTM FTP command are also affected by this # option. use_localtime=YES # # Activate logging of uploads/downloads. xferlog_enable=YES # # Make sure PORT transfer connections originate from port 20 (ftp-data). connect_from_port_20=YES # # If you want, you can arrange for uploaded anonymous files to be owned by # a different user. Note! Using "root" for uploaded files is not # recommended! #chown_uploads=YES #chown_username=whoever # # You may override where the log file goes if you like. The default is shown # below. #xferlog_file=/var/log/vsftpd.log # # If you want, you can have your log file in standard ftpd xferlog format. # Note that the default log file location is /var/log/xferlog in this case. #xferlog_std_format=YES # # You may change the default value for timing out an idle session. #idle_session_timeout=600 # # You may change the default value for timing out a data connection. #data_connection_timeout=120 # # It is recommended that you define on your system a unique user which the # ftp server can use as a totally isolated and unprivileged user. #nopriv_user=ftpsecure # # Enable this and the server will recognise asynchronous ABOR requests. Not # recommended for security (the code is non-trivial). Not enabling it, # however, may confuse older FTP clients. #async_abor_enable=YES # # By default the server will pretend to allow ASCII mode but in fact ignore # the request. Turn on the below options to have the server actually do ASCII # mangling on files when in ASCII mode. # Beware that on some FTP servers, ASCII support allows a denial of service # attack (DoS) via the command "SIZE /big/file" in ASCII mode. vsftpd # predicted this attack and has always been safe, reporting the size of the # raw file. # ASCII mangling is a horrible feature of the protocol. #ascii_upload_enable=YES #ascii_download_enable=YES # # You may fully customise the login banner string: #ftpd_banner=Welcome to blah FTP service. # # You may specify a file of disallowed anonymous e-mail addresses. Apparently # useful for combatting certain DoS attacks. #deny_email_enable=YES # (default follows) #banned_email_file=/etc/vsftpd.banned_emails # # You may restrict local users to their home directories. See the FAQ for # the possible risks in this before using chroot_local_user or # chroot_list_enable below. #chroot_local_user=YES # # You may specify an explicit list of local users to chroot() to their home # directory. If chroot_local_user is YES, then this list becomes a list of # users to NOT chroot(). #chroot_local_user=YES #chroot_list_enable=YES # (default follows) #chroot_list_file=/etc/vsftpd.chroot_list # # You may activate the "-R" option to the builtin ls. This is disabled by # default to avoid remote users being able to cause excessive I/O on large # sites. However, some broken FTP clients such as "ncftp" and "mirror" assume # the presence of the "-R" option, so there is a strong case for enabling it. #ls_recurse_enable=YES # # Debian customization # # Some of vsftpd's settings don't fit the Debian filesystem layout by # default. These settings are more Debian-friendly. # # This option should be the name of a directory which is empty. Also, the # directory should not be writable by the ftp user. This directory is used # as a secure chroot() jail at times vsftpd does not require filesystem # access. secure_chroot_dir=/var/run/vsftpd/empty # # This string is the name of the PAM service vsftpd will use. pam_service_name=vsftpd # # This option specifies the location of the RSA certificate to use for SSL # encrypted connections. rsa_cert_file=/etc/ssl/private/vsftpd.pem # SSL ssl_enable=YES allow_anon_ssl=NO force_local_data_ssl=YES force_local_logins_ssl=YES ssl_tlsv1=YES ssl_sslv2=YES ssl_sslv3=YES Thanks!

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  • Can't Get Virtual Users Setup in VSFTPD -Tried Everything

    - by N.T.
    Have Ubuntu 11.10 with vsftpd installed and working. Can not get virtual users setup at all? Vsftpd will allow main Ubuntu owner account to login, but nothing else? I've followed several tutorials on adding virtual users, but nothing works? I just need to add 2 virtual users and have them be able to upload files to vsftpd Ubuntu computer from other computers on my Lan network. Everywhere I've looked, people just point toward tutorials on adding virtual users, but that just is NOT working. I've been struggling with this for over a week now! PLEASE Help. Thanks. I'll even give a donation if someone can figure this out. here is the vsftpd.conf file I am using. I copied the original, and make a new one, every time I try a tutorial. So far, none have worked. Here is the vsftpd.conf file I'm using. (I hope this helps?) # Example config file /etc/vsftpd.conf # # The default compiled in settings are fairly paranoid. This sample file # loosens things up a bit, to make the ftp daemon more usable. # Please see vsftpd.conf.5 for all compiled in defaults. # # READ THIS: This example file is NOT an exhaustive list of vsftpd options. # Please read the vsftpd.conf.5 manual page to get a full idea of vsftpd's # capabilities. # # # Run standalone? vsftpd can run either from an inetd or as a standalone # daemon started from an initscript. listen=YES # # Run standalone with IPv6? # Like the listen parameter, except vsftpd will listen on an IPv6 socket # instead of an IPv4 one. This parameter and the listen parameter are mutually # exclusive. #listen_ipv6=YES # # Allow anonymous FTP? (Disabled by default) anonymous_enable=YES # # Uncomment this to allow local users to log in. local_enable=YES # # Uncomment this to enable any form of FTP write command. write_enable=YES # # Default umask for local users is 077. You may wish to change this to 022, # if your users expect that (022 is used by most other ftpd's) local_umask=022 # # Uncomment this to allow the anonymous FTP user to upload files. This only # has an effect if the above global write enable is activated. Also, you will # obviously need to create a directory writable by the FTP user. #anon_upload_enable=YES # # Uncomment this if you want the anonymous FTP user to be able to create # new directories. anon_mkdir_write_enable=YES # # Activate directory messages - messages given to remote users when they # go into a certain directory. dirmessage_enable=YES # # If enabled, vsftpd will display directory listings with the time # in your local time zone. The default is to display GMT. The # times returned by the MDTM FTP command are also affected by this # option. use_localtime=YES # # Activate logging of uploads/downloads. xferlog_enable=YES # # Make sure PORT transfer connections originate from port 20 (ftp-data). connect_from_port_20=YES # # If you want, you can arrange for uploaded anonymous files to be owned by # a different user. Note! Using "root" for uploaded files is not # recommended! #chown_uploads=YES #chown_username=whoever # # You may override where the log file goes if you like. The default is shown # below. #xferlog_file=/var/log/vsftpd.log # # If you want, you can have your log file in standard ftpd xferlog format. # Note that the default log file location is /var/log/xferlog in this case. xferlog_std_format=YES # # You may change the default value for timing out an idle session. #idle_session_timeout=600 # # You may change the default value for timing out a data connection. #data_connection_timeout=120 # # It is recommended that you define on your system a unique user which the # ftp server can use as a totally isolated and unprivileged user. #nopriv_user=ftpsecure # # Enable this and the server will recognise asynchronous ABOR requests. Not # recommended for security (the code is non-trivial). Not enabling it, # however, may confuse older FTP clients. #async_abor_enable=YES # # By default the server will pretend to allow ASCII mode but in fact ignore # the request. Turn on the below options to have the server actually do ASCII # mangling on files when in ASCII mode. # Beware that on some FTP servers, ASCII support allows a denial of service # attack (DoS) via the command "SIZE /big/file" in ASCII mode. vsftpd # predicted this attack and has always been safe, reporting the size of the # raw file. # ASCII mangling is a horrible feature of the protocol. #ascii_upload_enable=YES #ascii_download_enable=YES # # You may fully customise the login banner string: ftpd_banner=Welcome to Sage FTP service. # # You may specify a file of disallowed anonymous e-mail addresses. Apparently # useful for combatting certain DoS attacks. #deny_email_enable=YES # (default follows) #banned_email_file=/etc/vsftpd.banned_emails # # You may restrict local users to their home directories. See the FAQ for # the possible risks in this before using chroot_local_user or # chroot_list_enable below. chroot_local_user=YES # # You may specify an explicit list of local users to chroot() to their home # directory. If chroot_local_user is YES, then this list becomes a list of # users to NOT chroot(). #chroot_local_user=YES #chroot_list_enable=YES # (default follows) #chroot_list_file=/etc/vsftpd.chroot_list # # You may activate the "-R" option to the builtin ls. This is disabled by # default to avoid remote users being able to cause excessive I/O on large # sites. However, some broken FTP clients such as "ncftp" and "mirror" assume # the presence of the "-R" option, so there is a strong case for enabling it. #ls_recurse_enable=YES # # Debian customization # # Some of vsftpd's settings don't fit the Debian filesystem layout by # default. These settings are more Debian-friendly. # # This option should be the name of a directory which is empty. Also, the # directory should not be writable by the ftp user. This directory is used # as a secure chroot() jail at times vsftpd does not require filesystem # access. secure_chroot_dir=/var/run/vsftpd/empty # # This string is the name of the PAM service vsftpd will use. pam_service_name=vsftpd local_root=/media/FilesDrive # # This option specifies the location of the RSA certificate to use for SSL # encrypted connections. rsa_cert_file=/etc/ssl/private/vsftpd.pem

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  • ProFTPd server on Ubuntu getting access denied message when successfully authenticated?

    - by exxoid
    I have a Ubuntu box with a ProFTPD 1.3.4a Server, when I try to log in via my FTP Client I cannot do anything as it does not allow me to list directories; I have tried logging in as root and as a regular user and tried accessing different paths within the FTP Server. The error I get in my FTP Client is: Status: Retrieving directory listing... Command: CDUP Response: 250 CDUP command successful Command: PWD Response: 257 "/var" is the current directory Command: PASV Response: 227 Entering Passive Mode (172,16,4,22,237,205). Command: MLSD Response: 550 Access is denied. Error: Failed to retrieve directory listing Any idea? Here is the config of my proftpd: # # /etc/proftpd/proftpd.conf -- This is a basic ProFTPD configuration file. # To really apply changes, reload proftpd after modifications, if # it runs in daemon mode. It is not required in inetd/xinetd mode. # # Includes DSO modules Include /etc/proftpd/modules.conf # Set off to disable IPv6 support which is annoying on IPv4 only boxes. UseIPv6 off # If set on you can experience a longer connection delay in many cases. IdentLookups off ServerName "Drupal Intranet" ServerType standalone ServerIdent on "FTP Server ready" DeferWelcome on # Set the user and group that the server runs as User nobody Group nogroup MultilineRFC2228 on DefaultServer on ShowSymlinks on TimeoutNoTransfer 600 TimeoutStalled 600 TimeoutIdle 1200 DisplayLogin welcome.msg DisplayChdir .message true ListOptions "-l" DenyFilter \*.*/ # Use this to jail all users in their homes # DefaultRoot ~ # Users require a valid shell listed in /etc/shells to login. # Use this directive to release that constrain. # RequireValidShell off # Port 21 is the standard FTP port. Port 21 # In some cases you have to specify passive ports range to by-pass # firewall limitations. Ephemeral ports can be used for that, but # feel free to use a more narrow range. # PassivePorts 49152 65534 # If your host was NATted, this option is useful in order to # allow passive tranfers to work. You have to use your public # address and opening the passive ports used on your firewall as well. # MasqueradeAddress 1.2.3.4 # This is useful for masquerading address with dynamic IPs: # refresh any configured MasqueradeAddress directives every 8 hours <IfModule mod_dynmasq.c> # DynMasqRefresh 28800 </IfModule> # To prevent DoS attacks, set the maximum number of child processes # to 30. If you need to allow more than 30 concurrent connections # at once, simply increase this value. Note that this ONLY works # in standalone mode, in inetd mode you should use an inetd server # that allows you to limit maximum number of processes per service # (such as xinetd) MaxInstances 30 # Set the user and group that the server normally runs at. # Umask 022 is a good standard umask to prevent new files and dirs # (second parm) from being group and world writable. Umask 022 022 # Normally, we want files to be overwriteable. AllowOverwrite on # Uncomment this if you are using NIS or LDAP via NSS to retrieve passwords: # PersistentPasswd off # This is required to use both PAM-based authentication and local passwords AuthPAMConfig proftpd AuthOrder mod_auth_pam.c* mod_auth_unix.c # Be warned: use of this directive impacts CPU average load! # Uncomment this if you like to see progress and transfer rate with ftpwho # in downloads. That is not needed for uploads rates. # UseSendFile off TransferLog /var/log/proftpd/xferlog SystemLog /var/log/proftpd/proftpd.log # Logging onto /var/log/lastlog is enabled but set to off by default #UseLastlog on # In order to keep log file dates consistent after chroot, use timezone info # from /etc/localtime. If this is not set, and proftpd is configured to # chroot (e.g. DefaultRoot or <Anonymous>), it will use the non-daylight # savings timezone regardless of whether DST is in effect. #SetEnv TZ :/etc/localtime <IfModule mod_quotatab.c> QuotaEngine off </IfModule> <IfModule mod_ratio.c> Ratios off </IfModule> # Delay engine reduces impact of the so-called Timing Attack described in # http://www.securityfocus.com/bid/11430/discuss # It is on by default. <IfModule mod_delay.c> DelayEngine on </IfModule> <IfModule mod_ctrls.c> ControlsEngine off ControlsMaxClients 2 ControlsLog /var/log/proftpd/controls.log ControlsInterval 5 ControlsSocket /var/run/proftpd/proftpd.sock </IfModule> <IfModule mod_ctrls_admin.c> AdminControlsEngine off </IfModule> # # Alternative authentication frameworks # #Include /etc/proftpd/ldap.conf #Include /etc/proftpd/sql.conf # # This is used for FTPS connections # #Include /etc/proftpd/tls.conf # # Useful to keep VirtualHost/VirtualRoot directives separated # #Include /etc/proftpd/virtuals.con # A basic anonymous configuration, no upload directories. # <Anonymous ~ftp> # User ftp # Group nogroup # # We want clients to be able to login with "anonymous" as well as "ftp" # UserAlias anonymous ftp # # Cosmetic changes, all files belongs to ftp user # DirFakeUser on ftp # DirFakeGroup on ftp # # RequireValidShell off # # # Limit the maximum number of anonymous logins # MaxClients 10 # # # We want 'welcome.msg' displayed at login, and '.message' displayed # # in each newly chdired directory. # DisplayLogin welcome.msg # DisplayChdir .message # # # Limit WRITE everywhere in the anonymous chroot # <Directory *> # <Limit WRITE> # DenyAll # </Limit> # </Directory> # # # Uncomment this if you're brave. # # <Directory incoming> # # # Umask 022 is a good standard umask to prevent new files and dirs # # # (second parm) from being group and world writable. # # Umask 022 022 # # <Limit READ WRITE> # # DenyAll # # </Limit> # # <Limit STOR> # # AllowAll # # </Limit> # # </Directory> # # </Anonymous> # Include other custom configuration files Include /etc/proftpd/conf.d/ UseReverseDNS off <Global> RootLogin on UseFtpUsers on ServerIdent on DefaultChdir /var/www DeleteAbortedStores on LoginPasswordPrompt on AccessGrantMsg "You have been authenticated successfully." </Global> Any idea what could be wrong? Thanks for your help!

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  • PPTP ping client to client error

    - by Linux Intel
    I installed pptp server on a centos 6 64bit server PPTP Server ip : 55.66.77.10 PPTP Local ip : 10.0.0.1 Client1 IP : 10.0.0.60 centos 5 64bit Client2 IP : 10.0.0.61 centos5 64bit PPTP Server can ping Client1 And client 1 can ping PPTP Server PPTP Server can ping Client2 And client 2 can ping PPTP Server The problem is client 1 can not ping Client 2 route -n on PPTP Server Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.0.60 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 10.0.0.61 0.0.0.0 255.255.255.255 UH 0 0 0 ppp1 55.66.77.10 0.0.0.0 255.255.255.248 U 0 0 0 eth0 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth0 0.0.0.0 55.66.77.19 0.0.0.0 UG 0 0 0 eth0 route -n On Client 1 Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 55.66.77.10 70.14.13.19 255.255.255.255 UGH 0 0 0 eth0 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth1 0.0.0.0 70.14.13.19 0.0.0.0 UG 0 0 0 eth0 route -n On Client 2 Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.0.1 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0 55.66.77.10 84.56.120.60 255.255.255.255 UGH 0 0 0 eth1 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth0 0.0.0.0 84.56.120.60 0.0.0.0 UG 0 0 0 eth1 cat /etc/ppp/options.pptpd on PPTP server ############################################################################### # $Id: options.pptpd,v 1.11 2005/12/29 01:21:09 quozl Exp $ # # Sample Poptop PPP options file /etc/ppp/options.pptpd # Options used by PPP when a connection arrives from a client. # This file is pointed to by /etc/pptpd.conf option keyword. # Changes are effective on the next connection. See "man pppd". # # You are expected to change this file to suit your system. As # packaged, it requires PPP 2.4.2 and the kernel MPPE module. ############################################################################### # Authentication # Name of the local system for authentication purposes # (must match the second field in /etc/ppp/chap-secrets entries) name pptpd # Strip the domain prefix from the username before authentication. # (applies if you use pppd with chapms-strip-domain patch) #chapms-strip-domain # Encryption # (There have been multiple versions of PPP with encryption support, # choose with of the following sections you will use.) # BSD licensed ppp-2.4.2 upstream with MPPE only, kernel module ppp_mppe.o # {{{ refuse-pap refuse-chap refuse-mschap # Require the peer to authenticate itself using MS-CHAPv2 [Microsoft # Challenge Handshake Authentication Protocol, Version 2] authentication. require-mschap-v2 # Require MPPE 128-bit encryption # (note that MPPE requires the use of MSCHAP-V2 during authentication) require-mppe-128 # }}} # OpenSSL licensed ppp-2.4.1 fork with MPPE only, kernel module mppe.o # {{{ #-chap #-chapms # Require the peer to authenticate itself using MS-CHAPv2 [Microsoft # Challenge Handshake Authentication Protocol, Version 2] authentication. #+chapms-v2 # Require MPPE encryption # (note that MPPE requires the use of MSCHAP-V2 during authentication) #mppe-40 # enable either 40-bit or 128-bit, not both #mppe-128 #mppe-stateless # }}} # Network and Routing # If pppd is acting as a server for Microsoft Windows clients, this # option allows pppd to supply one or two DNS (Domain Name Server) # addresses to the clients. The first instance of this option # specifies the primary DNS address; the second instance (if given) # specifies the secondary DNS address. #ms-dns 10.0.0.1 #ms-dns 10.0.0.2 # If pppd is acting as a server for Microsoft Windows or "Samba" # clients, this option allows pppd to supply one or two WINS (Windows # Internet Name Services) server addresses to the clients. The first # instance of this option specifies the primary WINS address; the # second instance (if given) specifies the secondary WINS address. #ms-wins 10.0.0.3 #ms-wins 10.0.0.4 # Add an entry to this system's ARP [Address Resolution Protocol] # table with the IP address of the peer and the Ethernet address of this # system. This will have the effect of making the peer appear to other # systems to be on the local ethernet. # (you do not need this if your PPTP server is responsible for routing # packets to the clients -- James Cameron) proxyarp # Normally pptpd passes the IP address to pppd, but if pptpd has been # given the delegate option in pptpd.conf or the --delegate command line # option, then pppd will use chap-secrets or radius to allocate the # client IP address. The default local IP address used at the server # end is often the same as the address of the server. To override this, # specify the local IP address here. # (you must not use this unless you have used the delegate option) #10.8.0.100 # Logging # Enable connection debugging facilities. # (see your syslog configuration for where pppd sends to) debug # Print out all the option values which have been set. # (often requested by mailing list to verify options) #dump # Miscellaneous # Create a UUCP-style lock file for the pseudo-tty to ensure exclusive # access. lock # Disable BSD-Compress compression nobsdcomp # Disable Van Jacobson compression # (needed on some networks with Windows 9x/ME/XP clients, see posting to # poptop-server on 14th April 2005 by Pawel Pokrywka and followups, # http://marc.theaimsgroup.com/?t=111343175400006&r=1&w=2 ) novj novjccomp # turn off logging to stderr, since this may be redirected to pptpd, # which may trigger a loopback nologfd # put plugins here # (putting them higher up may cause them to sent messages to the pty) cat /etc/ppp/options.pptp on Client1 and Client2 ############################################################################### # $Id: options.pptp,v 1.3 2006/03/26 23:11:05 quozl Exp $ # # Sample PPTP PPP options file /etc/ppp/options.pptp # Options used by PPP when a connection is made by a PPTP client. # This file can be referred to by an /etc/ppp/peers file for the tunnel. # Changes are effective on the next connection. See "man pppd". # # You are expected to change this file to suit your system. As # packaged, it requires PPP 2.4.2 or later from http://ppp.samba.org/ # and the kernel MPPE module available from the CVS repository also on # http://ppp.samba.org/, which is packaged for DKMS as kernel_ppp_mppe. ############################################################################### # Lock the port lock # Authentication # We don't need the tunnel server to authenticate itself noauth # We won't do PAP, EAP, CHAP, or MSCHAP, but we will accept MSCHAP-V2 # (you may need to remove these refusals if the server is not using MPPE) refuse-pap refuse-eap refuse-chap refuse-mschap # Compression # Turn off compression protocols we know won't be used nobsdcomp nodeflate # Encryption # (There have been multiple versions of PPP with encryption support, # choose which of the following sections you will use. Note that MPPE # requires the use of MSCHAP-V2 during authentication) # # Note that using PPTP with MPPE and MSCHAP-V2 should be considered # insecure: # http://marc.info/?l=pptpclient-devel&m=134372640219039&w=2 # https://github.com/moxie0/chapcrack/blob/master/README.md # http://technet.microsoft.com/en-us/security/advisory/2743314 # http://ppp.samba.org/ the PPP project version of PPP by Paul Mackarras # ppp-2.4.2 or later with MPPE only, kernel module ppp_mppe.o # If the kernel is booted in FIPS mode (fips=1), the ppp_mppe.ko module # is not allowed and PPTP-MPPE is not available. # {{{ # Require MPPE 128-bit encryption #require-mppe-128 # }}} # http://mppe-mppc.alphacron.de/ fork from PPP project by Jan Dubiec # ppp-2.4.2 or later with MPPE and MPPC, kernel module ppp_mppe_mppc.o # {{{ # Require MPPE 128-bit encryption #mppe required,stateless # }}} IPtables are stopped on clients and server, Also net.ipv4.ip_forward = 1 is enabled on PPTP Server. How can i solve this problem .?

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  • How can I avoid Windows 8.1 resetting my font size?

    - by Michael Tsang
    I am using Windows 8.1 on my laptop, which has a 15.6" screen with resolution 1366x768. I measured the screen with a ruler and calculated its DPI, which is 101. Therefore, I have set the scaling to 105%. However, when I change to an external monitor, which is a huge one with resolution 1920x1080 and DPI 93, I need to change the scaling to 97% but when I change the DPI back and forth, my font sizes have get resetted. I prefer using font sizes 14 on my title bars, message boxes and icons and font sizes 13 on my palette titles, menus and tooltips. However, as my laptop screen is too small, in order to make my apps fit on screen, I use font sizes 12 on my title bars, message boxes and icons and font sizes 11 on my palette titles, menus and tooltips. I don't know why I can't resize the window to make it larger than my screen in Windows (but it is possible in Kubuntu), therefore, some parts of my apps cannot be shown with my preferred font size. I have tried changing both the DPI and the font size by using .reg files. Before switching to my laptop screen, I apply the following: Windows Registry Editor Version 5.00 [HKEY_CURRENT_USER\Control Panel\Desktop] "LogPixels"=dword:00000065 [HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics] "CaptionFont"=hex:ef,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,bc,02,00,00,\ 00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "SmCaptionFont"=hex:f0,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,bc,02,00,\ 00,00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "MenuFont"=hex:f0,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,00,\ 00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "StatusFont"=hex:f0,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\ 00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "MessageFont"=hex:ef,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\ 00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "IconFont"=hex:ef,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,00,\ 00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "AppliedDPI"=dword:00000065 Before switching to my external display, I apply this: Windows Registry Editor Version 5.00 [HKEY_CURRENT_USER\Control Panel\Desktop] "LogPixels"=dword:0000005d [HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics] "CaptionFont"=hex:ed,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,bc,02,00,00,\ 00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "SmCaptionFont"=hex:ee,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,bc,02,00,\ 00,00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "MenuFont"=hex:ef,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,00,\ 00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "StatusFont"=hex:ef,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\ 00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "MessageFont"=hex:ed,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\ 00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "IconFont"=hex:ed,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,00,\ 00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\ 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00 "AppliedDPI"=dword:0000005d I expect after applying the file, the DPI settings and the font sizes take effect at the next sign in. However, on my laptop screen, after I applied the file, signed out and in, the DPI setting changed, but the font sizes were resetted to tiny, and I had to apply the same file, signed out and in again to get the correct font size. The situation is even worse on my external monitor. After I applied the file, signed out and in, both the DPI setting and the font sizes were resetted to their default values, which were 96 DPI (the physical DPI as measured by dividing the resolution by the physical size is 93) and font size 9, which is totally unacceptable. How can I write the .reg files such that the settings can be correctly applied with a single sign in?

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  • IIS SSL Certificate Renewal Pain

    - by Rick Strahl
    I’m in the middle of my annual certificate renewal for the West Wind site and I can honestly say that I hate IIS’s certificate system.  When it works it’s fine, but when it doesn’t man can it be a pain. Because I deal with public certificates on my site merely once a year, and you have to perform the certificate dance just the right way, I seem to run into some sort of trouble every year, thinking that Microsoft surely must have addressed the issues I ran into previously – HA! Not so. Don’t ever use the Renew Certificate Feature in IIS! The first rule that I should have never forgotten is that certificate renewals in IIS (7 is what I’m using but I think it’s no different in 7.5 and 8), simply don’t work if you’re submitting to get a public certificate from a certificate authority. I use DNSimple for my DNS domain management and SSL certificates because they provide ridiculously easy domain management and good prices for SSL certs – especially wildcard certificates, which is what I use on west-wind.com. Certificates in IIS can be found pegged to the machine root. If you go into the IIS Manager, go to the machine root the tree and then click on certificates and you then get various certificate options: Both of these options create a new Certificate request (CSR), which is just a text file. But if you’re silly enough like me to click on the Renew button on your old certificate, you’ll find that you end up generating a very long Certificate Request that looks nothing like the original certificate request and the format that’s used for this is not accepted by most certificate authorities. While I’m not sure exactly what the problem is, it simply looks like IIS is respecting none of your original certificate bit size choices and is generating a huge certificate request that is 3 times the size of a ‘normal’ certificate request. The end result is (and I’ve done this at least twice now) is that the certificate processor is likely to fail processing those renewals. Always create a new Certificate While it’s a little more work and you have to remember how to fill out the certificate request properly, this is the safe way to make sure your certificate generates properly. First comes the Distinguished Name Properties dialog: Ah yes you have to love the nomenclature of this stuff. Distinguished name, Common name – WTF is a common name? It doesn’t look common to me! Make sure this form gets filled out correctly. Common NameThis is the domain name of the Web site. In my case I’m creating a wildcard certificate so I’m using the * prefix. If you’re purchasing a certificate for a specific domain use www.west-wind.com or store.west-wind.com for example. Make sure this matches the EXACT domain you’re trying to use secure access on because that’s all the certificate is going to work on unless you get a wildcard certificate. Organization Is the name of your company or organization. Depending on the kind of certificate you purchase this name will show up on your certificate. Most low end SSL certificates (ie. those that cost under $100 for single domains) don’t list the organization, the higher signature certificates that also require extensive validation by the cert authority do. Regardless you should make sure this matches the right company/organization. Organizational Unit This can be anything. Not really sure what this is for, but traditionally I’ve always set this to Web because – well this is a Web thing after all right? I’ve never seen this used anywhere that I can tell other than to internally reference the cert. State and CountryPretty obvious. Should reflect the location of the business/organization/person or site.   Next you have to configure the bit size used for the certificate: The default on this dialog is 1024, but I’ve found that most providers these days request a minimum bit length of 2048, as did my DNSimple provider. Again check with the provider when you submit to make sure. Bit length mismatches can cause problems if you use a size that isn’t supported by the provider. I had that happen last year when I submitted my CSR and it got rejected quite a bit later, when the certs usually are issued within an hour or less. When you’re done here, the certificate is saved to disk as a .txt file and it should look something like this (this is a 2048 bit length CSR):-----BEGIN NEW CERTIFICATE REQUEST----- MIIEVGCCAz0CAQAwdjELMAkGA1UEBhMCVVMxDzANBgNVBAgMBkhhd2FpaTENMAsG A1UEBwwEUGFpYTEfMB0GA1UECgwWV2VzdCBXaW5kIFRlY2hub2xvZ2llczEMMAoG B1UECwwDV2ViMRgwFgYDVQQDDA8qLndlc3Qtd2luZC5jb20wggEiMA0GCSqGSIb3 DQEBAQUAA4IBDwAwggEKAoIBAQDIPWOFMkMVRp2Ftj9w/cCVV4OYYhoZYtl+8lTk oqDwKca0xWHLgioX/9v0rZLS6a82MHqKEBxVXu+cuCmSE4AQtB/1YH9lS4tpc/be OZDvnTotP6l4MCEzzAfROcw4CiIg6X0RMSnl8IATAvv2V5LQM9TDdt9oDdMpX2IY +vVC9RZ7PMHBmR9kwI2i/lrKitzhQKaHgpmKcRlM6iqpALUiX28w5HJaDKK1MDHN 607tyFJLHijuJKx7PdTqZYf50KkC3NupfZ2avVycf18Q13jHWj59tvwEOczoVzRL l4LQivAqbhyiqMpWnrZunIOUZta5aGm+jo7O1knGWJjxuraTAgMBAAGgggGYMBoG CisGAQQBgjcNAgMxDBYKNi4yLjkyMDAuMjA0BgkrBgEEAYI3FRQxJzAlAgEFDAZS QVNYUFMMC1JBU1hQU1xSaWNrDAtJbmV0TWdyLmV4ZTByBgorBgEEAYI3DQICMWQw YgIBAR5aAE0AaQBjAHIAbwBzAG8AZgB0ACAAUgBTAEEAIABTAEMAaABhAG4AbgBl AGwAIABDAHIAeQBwAHQAbwBnAHIAYQBwAGgAaQBjACAAUAByAG8AdgBpAGQAZQBy AwEAMIHPBgkqhkiG9w0BCQ4xgcEwgb4wDgYDVR0PAQH/BAQDAgTwMBMGA1UdJQQM MAoGCCsGAQUFBwMBMHgGCSqGSIb3DQEJDwRrMGkwDgYIKoZIhvcNAwICAgCAMA4G CCqGSIb3DQMEAgIAgDALBglghkgBZQMEASowCwYJYIZIAWUDBAEtMAsGCWCGSAFl AwQBAjALBglghkgBZQMEAQUwBwYFKw4DAgcwCgYIKoZIhvcNAwcwHQYDVR0OBBYE FD/yOsTbXE+GVFCFMmldzQvyloz9MA0GCSqGSIb3DQEBBQUAA4IBAQCK6LlsCuIM 1AU0niB6QZ9v0FTsGFxP1dYvVUnJyY6VEKNiGFiQjZac7UCs0p58yScdXWEFOE8V OsjAYD3xYNc05+ckyD67UHRGEUAVB9RBvbKW23KeR/8kBmEzc8PemD52YOgExxAJ 57xWmAwEHAvbgYzQvhO8AOzH3TGvvHbg5UKM1pYgNmuwZq5DkL/IDoeIJwfk/wrI wghNTuxxIFgbH4YrgLgv4PRvrS/LaTCRBdboaCgzATMczaOb1nd/DVNR+3fCtMhM W0psTAjzRbmXF3nJyAQa7jF/52gkY0RfFX2lG5tJnG+XDsVNvKNvh9Qa5Tlmkm06 ILKCm9ciWCKk -----END NEW CERTIFICATE REQUEST----- You can take that certificate request and submit that to your certificate provider. Since this is base64 encoded you can typically just paste it into a text box on the submission page, or some providers will ask you to upload the CSR as a file. What does a Renewal look like? Note the length of the CSR will vary somewhat with key strength, but compare this to a renewal request that IIS generated from my existing site:-----BEGIN NEW CERTIFICATE REQUEST----- MIIPpwYFKoZIhvcNAQcCoIIPmDCCD5QCAQExCzAJBgUrDgMCGgUAMIIIqAYJKoZI hvcNAQcBoIIImQSCCJUwggiRMIIH+gIBADBdMSEwHwYDVQQLDBhEb21haW4gQ29u dHJvbCBWYWxpFGF0ZWQxHjAcBgNVBAsMFUVzc2VudGlhbFNTTCBXaWxkY2FyZDEY MBYGA1UEAwwPKi53ZXN0LXdpbmQuY29tMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCB iQKBgQCK4OuIOR18Wb8tNMGRZiD1c9X57b332Lj7DhbckFqLs0ys8kVDHrTXSj+T Ye9nmAvfPpZmBtE5p9qRNN79rUYugAdl+qEtE4IJe1bRfxXzcKa1SXa8+TEs3zQa zYSmcR2dDuC8om1eAdeCtt0NnkvANgm1VLwGOor/UHMASaEhCQIDAQABoIIG8jAa BgorBgEEAYI3DQIDMQwWCjYuMi45MjAwLjIwNAYJKwYBBAGCNxUUMScwJQIBBQwG UkFTWFBTDAtSQVNYUFNcUmljawwLSW5ldE1nci5leGUwZgYKKwYBBAGCNw0CAjFY MFYCAQIeTgBNAGkAYwByAG8AcwBvAGYAdAAgAFMAdAByAG8AbgBnACAAQwByAHkA cAB0AG8AZwByAGEAcABoAGkAYwAgAFAAcgBvAHYAaQBkAGUAcgMBADCCAQAGCSqG SIb3DQEJDjGB8jCB7zAOBgNVHQ8BAf8EBAMCBaAwDAYDVR0TAQH/BAIwADA0BgNV 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+XZ8bhM7vsAS+pZionR4MyuQ0mYIt/lDcsZVZ91KxTsIm8rNMkkYGFoSIXjQ0+0t CbxMF0i2qnpmNRpA6PU8l7lxxvPkplsk9KB8QIPFrR5p/i/SUAd9vECWh5+/ktlc rfFP2PK7XcEwWizsvMrNqLyvQVNXSUPTMYIBrzCCAasCAQEwgYcwcjELMAkGA1UE BhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2Fs Zm9yZDEaMBgGA1UEChMRQ09NT0RPIENBIExpbWl0ZWQxGDAWBgNVBAMTD0Vzc2Vu dGlhbFNTTCBDQQIRAO7UTVPkm+2Sbks59IdptaUwCQYFKw4DAhoFADANBgkqhkiG 9w0BAQEFAASCAQB8PNQ6bYnQpWfkHyxnDuvNKw3wrqF2p7JMZm+SuN2qp3R2LpCR mW2LrGtQIm9Iob/QOYH+8houYNVdvsATGPXX2T8gzn+anof4tOG0vCTK1Bp9bwf9 MkRP+1c8RW/vkYmUW4X5/C+y3CZpMH5dDTaXBIpXFzjX/fxNpH/rvLzGiaYYL3Cn OLO+aOADr9qq5yoqwpiYCSfYNNYKTUNNGfYIidQwYtbHXEYhSukB2oR89xD2sZZ4 bOqFjUPgTa5SsERLDDeg3omMKiIXVYGxlqBEq51Kge6IQt4qQV9P9VgInW7cWmKe dTqNHI9ri3ttewdEnT++TKGKKfTjX9SR8Waj -----END NEW CERTIFICATE REQUEST----- Clearly there’s something very different between this an my original request! And it didn’t work. IIS creates a custom CSR that is encoded in a format that no certificate authority I’ve ever used uses. If you want the gory details of what’s in there look at this ServerFault question (thanks to Mika in the comments). In the end it doesn’t matter  though – no certificate authority knows what to do with this CSR. So create a new CSR and skip the renewal. Always! Use the same Server Keep in mind that on IIS at least you should always create your certificate on a single server and then when you receive the final certificate from your provider import it on that server. IIS tracks the CSR it created and requires it in order to import the final certificate properly. So if for some reason you try to install the certificate on another server, it won’t work. I’ve also run into trouble trying to install the same certificate twice – this time around I didn’t give my certificate the proper friendly name and IIS failed to allow me to assign the certificate to any of my Web sites. So I removed the certificate and tried to import again, only to find it failed the second time around. There are other ways to fix this, but in my case I had to have the certificate re-issued to work – not what you want to do. Regardless of what you do though, when you import make sure you do it right the first time by crossing all your t’s and dotting your i's– it’ll save you a lot of grief! You don’t actually have to use the server that the certificate gets installed on to generate the CSR and first install it, but it is generally a good idea to do so just so you can get the certificate installed into the right place right away. If you have access to the server where you need to install the certificate you might as well use it. But you can use another machine to generated the and install the certificate, then export the certificate and move it to another machine as needed. So you can use your Dev machine to create a certificate then export it and install it on a live server. More on installation and back up/export later. Installing the Certificate Once you’ve submitted a CSR request your provider will process the request and eventually issue you a new final certificate that contains another text file with the final key to import into your certificate store. IIS does this by combining the content in your certificate request with the original CSR. If all goes well your new certificate shows up in the certificate list and you’re ready to assign the certificate to your sites. Make sure you use a friendly name that matches domain name of your site. So use *.mysite.com or www.mysite.com or store.mysite.com to ensure IIS recognizes the certificate. I made the mistake of not naming my friendly name this way and found that IIS was unable to link my sites to my wildcard certificate. It needed to have the *. as part of the certificate otherwise the Hostname input field was blanked out. Changing the Friendly Name If you by accidentally used an invalid friendly name you can change it later in the Windows certificate store. Bring up a Run Box Type MMC File | Add/Remove Snap In Add Certificates | Computer Account | Local Computer Drill into Certificates | Personal | Certificates Find your Certificate | Right Click | Properties Edit the Friendly Name | Click OK Backing up your Certificate The first thing you should do once your certificate is successfully installed is to back it up! In case your server crashes or you otherwise lose your configuration this will ensure you have an easy way to recover and reinstall your certificate either on the same server or a different one. If you’re running a server farm or using a wildcard certificate you also need to get the certificate onto other machines and a PFX file import is the easiest way to do this. To back up your certificate select your certificate and choose Export from the context or sidebar menu: The Export Certificate option allows you to export a password protected binary file that you can import in a single step. You can copy the resulting binary PFX file to back up or copy to other machines to install on. Importing the certificate on another machine is as easy as pointing at the PFX file and specifying the password. IIS handles the rest. Assigning a new certificate to your Site Once you have the new certificate installed, all that’s left to do is assign it to your site. In IIS select your Web site and bring up the Site Bindings from the right sidebar. Add a new binding for https, bind it to port 443, specify your hostname and pick the certificate from the pick list. If you’re using a root site make sure to set up your certificate for www.yoursite.com and also for yoursite.com so that both work properly with SSL. Note that you need to explicitly configure each hostname for a certificate if you plan to use SSL. Luckily if you update your SSL certificate in the following year, IIS prompts you and asks whether you like to update all other sites that are using the existing cert to the newer cert. And you’re done. So what’s the Pain? So, all of this is old hat and it doesn’t look all that bad right? So what’s the pain here? Well if you follow the instructions and do everything right, then the process is about as straight forward as you would expect it to be. You create a cert request, you import it and assign it to your sites. That’s the basic steps and to be perfectly fair it works well – if nothing goes wrong. However, renewing tends to be the problem. The first unintuitive issue is that you simply shouldn’t renew but create a new CSR and generate your new certificate from that. Over the years I’ve fallen prey to the belief that Microsoft eventually will fix this so that the renewal creates the same type of CSR as the old cert, but apparently that will just never happen. Booo! The other problem I ran into is that I accidentally misnamed my imported certificate which in turn set off a chain of events that caused my originally issued certificate to become uninstallable. When I received my completed certificate I installed it and it installed just fine, but the friendly name was wrong. As a result IIS refused to assign the certificate to any of my host headered sites. That’s strike number one. Why the heck should the friendly name have any effect on the ability to attach the certificate??? Next I uninstalled the certificate because I figured that would be the easiest way to make sure I get it right. But I found that I could not reinstall my certificate. I kept getting these stop errors: "ASN1 bad tag value met" that would prevent the installation from completion. After searching around for this error and reading countless long messages on forums, I found that this error supposedly does not actually mean the install failed, but the list wouldn’t refresh. Commodo has this to say: Note: There is a known issue in IIS 7 giving the following error: "Cannot find the certificate request associated with this certificate file. A certificate request must be completed on the computer where it was created." You may also receive a message stating "ASN1 bad tag value met". If this is the same server that you generated the CSR on then, in most cases, the certificate is actually installed. Simply cancel the dialog and press "F5" to refresh the list of server certificates. If the new certificate is now in the list, you can continue with the next step. If it is not in the list, you will need to reissue your certificate using a new CSR (see our CSR creation instructions for IIS 7). After creating a new CSR, login to your Comodo account and click the 'replace' button for your certificate. Not sure if this issue is fixed in IIS 8 but that’s an insane bug to have crop up. As it turns out, in my case the refresh didn’t work and the certificate didn’t show up in the IIS list after the reinstall. In fact when looking at the certificate store I could see my certificate was installed in the right place, but the private key is missing which is most likely why IIS is not picking it up. It looks like IIS could not match the final cert to the original CSR generated. But again some sort of message to that affect might be helpful instead of ASN1 bad tag value met. Recovering the Private Key So it turns out my original problem was that I received the published key, but when I imported the private key was missing. There’s a relatively easy way to recover from this. If your certificate doesn’t show up in IIS check in the certificate store for the local machine (see steps above on how to bring this up). If you look at the certificate in Certificates/Personal/Certificates make sure you see the key as shown in the image below: if the key is missing it means that the certificate is missing the private key most likely. To fix a certificate you can do the following: Double click the certificate Go to the Details Tab Copy down the Serial number You can copy the serial number from the area blurred out above. The serial number will be in a format like ?00 a7 9b a1 a4 9d 91 63 57 d6 9f 26 b8 ee 79 b5 cb and you’ll need to strip out the spaces in order to use it in the next step. Next open up an Administrative command prompt and issue the following command: certutil -repairstore my 00a79ba1a49d916357d69f26b8ee79b5cb You should get a confirmation message that the repair worked. If you now go back to the certificate store you should now see the key icon show up on the certificate. Your certificate is fixed. Now go back into IIS Manager and refresh the list of certificates and if all goes well you should see all the certificates that showed in the cert store now: Remember – back up the key first then map to your site… Summary I deal with a lot of customers who run their own IIS servers, and I can’t tell you how often I hear about botched SSL installations. When I posted some of my issues on Twitter yesterday I got a hell storm of “me too” responses. I’m clearly not the only one, who’s run into this especially with renewals. I feel pretty comfortable with IIS configuration and I do a lot of it for support purposes, but the SSL configuration is one that never seems to go seamlessly. This blog post is meant as reminder to myself to read next time I do a renewal. So I can dot my i's and dash my t’s before I get caught in the mess I’m dealing with today. Hopefully some of you find this useful as well.© Rick Strahl, West Wind Technologies, 2005-2014Posted in IIS7  Security   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Creating STA COM compatible ASP.NET Applications

    - by Rick Strahl
    When building ASP.NET applications that interface with old school COM objects like those created with VB6 or Visual FoxPro (MTDLL), it's extremely important that the threads that are serving requests use Single Threaded Apartment Threading. STA is a COM built-in technology that allows essentially single threaded components to operate reliably in a multi-threaded environment. STA's guarantee that COM objects instantiated on a specific thread stay on that specific thread and any access to a COM object from another thread automatically marshals that thread to the STA thread. The end effect is that you can have multiple threads, but a COM object instance lives on a fixed never changing thread. ASP.NET by default uses MTA (multi-threaded apartment) threads which are truly free spinning threads that pay no heed to COM object marshaling. This is vastly more efficient than STA threading which has a bit of overhead in determining whether it's OK to run code on a given thread or whether some sort of thread/COM marshaling needs to occur. MTA COM components can be very efficient, but STA COM components in a multi-threaded environment always tend to have a fair amount of overhead. It's amazing how much COM Interop I still see today so while it seems really old school to be talking about this topic, it's actually quite apropos for me as I have many customers using legacy COM systems that need to interface with other .NET applications. In this post I'm consolidating some of the hacks I've used to integrate with various ASP.NET technologies when using STA COM Components. STA in ASP.NET Support for STA threading in the ASP.NET framework is fairly limited. Specifically only the original ASP.NET WebForms technology supports STA threading directly via its STA Page Handler implementation or what you might know as ASPCOMPAT mode. For WebForms running STA components is as easy as specifying the ASPCOMPAT attribute in the @Page tag:<%@ Page Language="C#" AspCompat="true" %> which runs the page in STA mode. Removing it runs in MTA mode. Simple. Unfortunately all other ASP.NET technologies built on top of the core ASP.NET engine do not support STA natively. So if you want to use STA COM components in MVC or with class ASMX Web Services, there's no automatic way like the ASPCOMPAT keyword available. So what happens when you run an STA COM component in an MTA application? In low volume environments - nothing much will happen. The COM objects will appear to work just fine as there are no simultaneous thread interactions and the COM component will happily run on a single thread or multiple single threads one at a time. So for testing running components in MTA environments may appear to work just fine. However as load increases and threads get re-used by ASP.NET COM objects will end up getting created on multiple different threads. This can result in crashes or hangs, or data corruption in the STA components which store their state in thread local storage on the STA thread. If threads overlap this global store can easily get corrupted which in turn causes problems. STA ensures that any COM object instance loaded always stays on the same thread it was instantiated on. What about COM+? COM+ is supposed to address the problem of STA in MTA applications by providing an abstraction with it's own thread pool manager for COM objects. It steps in to the COM instantiation pipeline and hands out COM instances from its own internally maintained STA Thread pool. This guarantees that the COM instantiation threads are STA threads if using STA components. COM+ works, but in my experience the technology is very, very slow for STA components. It adds a ton of overhead and reduces COM performance noticably in load tests in IIS. COM+ can make sense in some situations but for Web apps with STA components it falls short. In addition there's also the need to ensure that COM+ is set up and configured on the target machine and the fact that components have to be registered in COM+. COM+ also keeps components up at all times, so if a component needs to be replaced the COM+ package needs to be unloaded (same is true for IIS hosted components but it's more common to manage that). COM+ is an option for well established components, but native STA support tends to provide better performance and more consistent usability, IMHO. STA for non supporting ASP.NET Technologies As mentioned above only WebForms supports STA natively. However, by utilizing the WebForms ASP.NET Page handler internally it's actually possible to trick various other ASP.NET technologies and let them work with STA components. This is ugly but I've used each of these in various applications and I've had minimal problems making them work with FoxPro STA COM components which is about as dififcult as it gets for COM Interop in .NET. In this post I summarize several STA workarounds that enable you to use STA threading with these ASP.NET Technologies: ASMX Web Services ASP.NET MVC WCF Web Services ASP.NET Web API ASMX Web Services I start with classic ASP.NET ASMX Web Services because it's the easiest mechanism that allows for STA modification. It also clearly demonstrates how the WebForms STA Page Handler is the key technology to enable the various other solutions to create STA components. Essentially the way this works is to override the WebForms Page class and hijack it's init functionality for processing requests. Here's what this looks like for Web Services:namespace FoxProAspNet { public class WebServiceStaHandler : System.Web.UI.Page, IHttpAsyncHandler { protected override void OnInit(EventArgs e) { IHttpHandler handler = new WebServiceHandlerFactory().GetHandler( this.Context, this.Context.Request.HttpMethod, this.Context.Request.FilePath, this.Context.Request.PhysicalPath); handler.ProcessRequest(this.Context); this.Context.ApplicationInstance.CompleteRequest(); } public IAsyncResult BeginProcessRequest( HttpContext context, AsyncCallback cb, object extraData) { return this.AspCompatBeginProcessRequest(context, cb, extraData); } public void EndProcessRequest(IAsyncResult result) { this.AspCompatEndProcessRequest(result); } } public class AspCompatWebServiceStaHandlerWithSessionState : WebServiceStaHandler, IRequiresSessionState { } } This class overrides the ASP.NET WebForms Page class which has a little known AspCompatBeginProcessRequest() and AspCompatEndProcessRequest() method that is responsible for providing the WebForms ASPCOMPAT functionality. These methods handle routing requests to STA threads. Note there are two classes - one that includes session state and one that does not. If you plan on using ASP.NET Session state use the latter class, otherwise stick to the former. This maps to the EnableSessionState page setting in WebForms. This class simply hooks into this functionality by overriding the BeginProcessRequest and EndProcessRequest methods and always forcing it into the AspCompat methods. The way this works is that BeginProcessRequest() fires first to set up the threads and starts intializing the handler. As part of that process the OnInit() method is fired which is now already running on an STA thread. The code then creates an instance of the actual WebService handler factory and calls its ProcessRequest method to start executing which generates the Web Service result. Immediately after ProcessRequest the request is stopped with Application.CompletRequest() which ensures that the rest of the Page handler logic doesn't fire. This means that even though the fairly heavy Page class is overridden here, it doesn't end up executing any of its internal processing which makes this code fairly efficient. In a nutshell, we're highjacking the Page HttpHandler and forcing it to process the WebService process handler in the context of the AspCompat handler behavior. Hooking up the Handler Because the above is an HttpHandler implementation you need to hook up the custom handler and replace the standard ASMX handler. To do this you need to modify the web.config file (here for IIS 7 and IIS Express): <configuration> <system.webServer> <handlers> <remove name="WebServiceHandlerFactory-Integrated-4.0" /> <add name="Asmx STA Web Service Handler" path="*.asmx" verb="*" type="FoxProAspNet.WebServiceStaHandler" precondition="integrated"/> </handlers> </system.webServer> </configuration> (Note: The name for the WebServiceHandlerFactory-Integrated-4.0 might be slightly different depending on your server version. Check the IIS Handler configuration in the IIS Management Console for the exact name or simply remove the handler from the list there which will propagate to your web.config). For IIS 5 & 6 (Windows XP/2003) or the Visual Studio Web Server use:<configuration> <system.web> <httpHandlers> <remove path="*.asmx" verb="*" /> <add path="*.asmx" verb="*" type="FoxProAspNet.WebServiceStaHandler" /> </httpHandlers> </system.web></configuration> To test, create a new ASMX Web Service and create a method like this: [WebService(Namespace = "http://foxaspnet.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] public class FoxWebService : System.Web.Services.WebService { [WebMethod] public string HelloWorld() { return "Hello World. Threading mode is: " + System.Threading.Thread.CurrentThread.GetApartmentState(); } } Run this before you put in the web.config configuration changes and you should get: Hello World. Threading mode is: MTA Then put the handler mapping into Web.config and you should see: Hello World. Threading mode is: STA And you're on your way to using STA COM components. It's a hack but it works well! I've used this with several high volume Web Service installations with various customers and it's been fast and reliable. ASP.NET MVC ASP.NET MVC has quickly become the most popular ASP.NET technology, replacing WebForms for creating HTML output. MVC is more complex to get started with, but once you understand the basic structure of how requests flow through the MVC pipeline it's easy to use and amazingly flexible in manipulating HTML requests. In addition, MVC has great support for non-HTML output sources like JSON and XML, making it an excellent choice for AJAX requests without any additional tools. Unlike WebForms ASP.NET MVC doesn't support STA threads natively and so some trickery is needed to make it work with STA threads as well. MVC gets its handler implementation through custom route handlers using ASP.NET's built in routing semantics. To work in an STA handler requires working in the Page Handler as part of the Route Handler implementation. As with the Web Service handler the first step is to create a custom HttpHandler that can instantiate an MVC request pipeline properly:public class MvcStaThreadHttpAsyncHandler : Page, IHttpAsyncHandler, IRequiresSessionState { private RequestContext _requestContext; public MvcStaThreadHttpAsyncHandler(RequestContext requestContext) { if (requestContext == null) throw new ArgumentNullException("requestContext"); _requestContext = requestContext; } public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData) { return this.AspCompatBeginProcessRequest(context, cb, extraData); } protected override void OnInit(EventArgs e) { var controllerName = _requestContext.RouteData.GetRequiredString("controller"); var controllerFactory = ControllerBuilder.Current.GetControllerFactory(); var controller = controllerFactory.CreateController(_requestContext, controllerName); if (controller == null) throw new InvalidOperationException("Could not find controller: " + controllerName); try { controller.Execute(_requestContext); } finally { controllerFactory.ReleaseController(controller); } this.Context.ApplicationInstance.CompleteRequest(); } public void EndProcessRequest(IAsyncResult result) { this.AspCompatEndProcessRequest(result); } public override void ProcessRequest(HttpContext httpContext) { throw new NotSupportedException("STAThreadRouteHandler does not support ProcessRequest called (only BeginProcessRequest)"); } } This handler code figures out which controller to load and then executes the controller. MVC internally provides the information needed to route to the appropriate method and pass the right parameters. Like the Web Service handler the logic occurs in the OnInit() and performs all the processing in that part of the request. Next, we need a RouteHandler that can actually pick up this handler. Unlike the Web Service handler where we simply registered the handler, MVC requires a RouteHandler to pick up the handler. RouteHandlers look at the URL's path and based on that decide on what handler to invoke. The route handler is pretty simple - all it does is load our custom handler: public class MvcStaThreadRouteHandler : IRouteHandler { public IHttpHandler GetHttpHandler(RequestContext requestContext) { if (requestContext == null) throw new ArgumentNullException("requestContext"); return new MvcStaThreadHttpAsyncHandler(requestContext); } } At this point you can instantiate this route handler and force STA requests to MVC by specifying a route. The following sets up the ASP.NET Default Route:Route mvcRoute = new Route("{controller}/{action}/{id}", new RouteValueDictionary( new { controller = "Home", action = "Index", id = UrlParameter.Optional }), new MvcStaThreadRouteHandler()); RouteTable.Routes.Add(mvcRoute);   To make this code a little easier to work with and mimic the behavior of the routes.MapRoute() functionality extension method that MVC provides, here is an extension method for MapMvcStaRoute(): public static class RouteCollectionExtensions { public static void MapMvcStaRoute(this RouteCollection routeTable, string name, string url, object defaults = null) { Route mvcRoute = new Route(url, new RouteValueDictionary(defaults), new MvcStaThreadRouteHandler()); RouteTable.Routes.Add(mvcRoute); } } With this the syntax to add  route becomes a little easier and matches the MapRoute() method:RouteTable.Routes.MapMvcStaRoute( name: "Default", url: "{controller}/{action}/{id}", defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional } ); The nice thing about this route handler, STA Handler and extension method is that it's fully self contained. You can put all three into a single class file and stick it into your Web app, and then simply call MapMvcStaRoute() and it just works. Easy! To see whether this works create an MVC controller like this: public class ThreadTestController : Controller { public string ThreadingMode() { return Thread.CurrentThread.GetApartmentState().ToString(); } } Try this test both with only the MapRoute() hookup in the RouteConfiguration in which case you should get MTA as the value. Then change the MapRoute() call to MapMvcStaRoute() leaving all the parameters the same and re-run the request. You now should see STA as the result. You're on your way using STA COM components reliably in ASP.NET MVC. WCF Web Services running through IIS WCF Web Services provide a more robust and wider range of services for Web Services. You can use WCF over HTTP, TCP, and Pipes, and WCF services support WS* secure services. There are many features in WCF that go way beyond what ASMX can do. But it's also a bit more complex than ASMX. As a basic rule if you need to serve straight SOAP Services over HTTP I 'd recommend sticking with the simpler ASMX services especially if COM is involved. If you need WS* support or want to serve data over non-HTTP protocols then WCF makes more sense. WCF is not my forte but I found a solution from Scott Seely on his blog that describes the progress and that seems to work well. I'm copying his code below so this STA information is all in one place and quickly explain. Scott's code basically works by creating a custom OperationBehavior which can be specified via an [STAOperation] attribute on every method. Using his attribute you end up with a class (or Interface if you separate the contract and class) that looks like this: [ServiceContract] public class WcfService { [OperationContract] public string HelloWorldMta() { return Thread.CurrentThread.GetApartmentState().ToString(); } // Make sure you use this custom STAOperationBehavior // attribute to force STA operation of service methods [STAOperationBehavior] [OperationContract] public string HelloWorldSta() { return Thread.CurrentThread.GetApartmentState().ToString(); } } Pretty straight forward. The latter method returns STA while the former returns MTA. To make STA work every method needs to be marked up. The implementation consists of the attribute and OperationInvoker implementation. Here are the two classes required to make this work from Scott's post:public class STAOperationBehaviorAttribute : Attribute, IOperationBehavior { public void AddBindingParameters(OperationDescription operationDescription, System.ServiceModel.Channels.BindingParameterCollection bindingParameters) { } public void ApplyClientBehavior(OperationDescription operationDescription, System.ServiceModel.Dispatcher.ClientOperation clientOperation) { // If this is applied on the client, well, it just doesn’t make sense. // Don’t throw in case this attribute was applied on the contract // instead of the implementation. } public void ApplyDispatchBehavior(OperationDescription operationDescription, System.ServiceModel.Dispatcher.DispatchOperation dispatchOperation) { // Change the IOperationInvoker for this operation. dispatchOperation.Invoker = new STAOperationInvoker(dispatchOperation.Invoker); } public void Validate(OperationDescription operationDescription) { if (operationDescription.SyncMethod == null) { throw new InvalidOperationException("The STAOperationBehaviorAttribute " + "only works for synchronous method invocations."); } } } public class STAOperationInvoker : IOperationInvoker { IOperationInvoker _innerInvoker; public STAOperationInvoker(IOperationInvoker invoker) { _innerInvoker = invoker; } public object[] AllocateInputs() { return _innerInvoker.AllocateInputs(); } public object Invoke(object instance, object[] inputs, out object[] outputs) { // Create a new, STA thread object[] staOutputs = null; object retval = null; Thread thread = new Thread( delegate() { retval = _innerInvoker.Invoke(instance, inputs, out staOutputs); }); thread.SetApartmentState(ApartmentState.STA); thread.Start(); thread.Join(); outputs = staOutputs; return retval; } public IAsyncResult InvokeBegin(object instance, object[] inputs, AsyncCallback callback, object state) { // We don’t handle async… throw new NotImplementedException(); } public object InvokeEnd(object instance, out object[] outputs, IAsyncResult result) { // We don’t handle async… throw new NotImplementedException(); } public bool IsSynchronous { get { return true; } } } The key in this setup is the Invoker and the Invoke method which creates a new thread and then fires the request on this new thread. Because this approach creates a new thread for every request it's not super efficient. There's a bunch of overhead involved in creating the thread and throwing it away after each thread, but it'll work for low volume requests and insure each thread runs in STA mode. If better performance is required it would be useful to create a custom thread manager that can pool a number of STA threads and hand off threads as needed rather than creating new threads on every request. If your Web Service needs are simple and you need only to serve standard SOAP 1.x requests, I would recommend sticking with ASMX services. It's easier to set up and work with and for STA component use it'll be significantly better performing since ASP.NET manages the STA thread pool for you rather than firing new threads for each request. One nice thing about Scotts code is though that it works in any WCF environment including self hosting. It has no dependency on ASP.NET or WebForms for that matter. STA - If you must STA components are a  pain in the ass and thankfully there isn't too much stuff out there anymore that requires it. But when you need it and you need to access STA functionality from .NET at least there are a few options available to make it happen. Each of these solutions is a bit hacky, but they work - I've used all of them in production with good results with FoxPro components. I hope compiling all of these in one place here makes it STA consumption a little bit easier. I feel your pain :-) Resources Download STA Handler Code Examples Scott Seely's original STA WCF OperationBehavior Article© Rick Strahl, West Wind Technologies, 2005-2012Posted in FoxPro   ASP.NET  .NET  COM   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Improving Partitioned Table Join Performance

    - by Paul White
    The query optimizer does not always choose an optimal strategy when joining partitioned tables. This post looks at an example, showing how a manual rewrite of the query can almost double performance, while reducing the memory grant to almost nothing. Test Data The two tables in this example use a common partitioning partition scheme. The partition function uses 41 equal-size partitions: CREATE PARTITION FUNCTION PFT (integer) AS RANGE RIGHT FOR VALUES ( 125000, 250000, 375000, 500000, 625000, 750000, 875000, 1000000, 1125000, 1250000, 1375000, 1500000, 1625000, 1750000, 1875000, 2000000, 2125000, 2250000, 2375000, 2500000, 2625000, 2750000, 2875000, 3000000, 3125000, 3250000, 3375000, 3500000, 3625000, 3750000, 3875000, 4000000, 4125000, 4250000, 4375000, 4500000, 4625000, 4750000, 4875000, 5000000 ); GO CREATE PARTITION SCHEME PST AS PARTITION PFT ALL TO ([PRIMARY]); There two tables are: CREATE TABLE dbo.T1 ( TID integer NOT NULL IDENTITY(0,1), Column1 integer NOT NULL, Padding binary(100) NOT NULL DEFAULT 0x,   CONSTRAINT PK_T1 PRIMARY KEY CLUSTERED (TID) ON PST (TID) );   CREATE TABLE dbo.T2 ( TID integer NOT NULL, Column1 integer NOT NULL, Padding binary(100) NOT NULL DEFAULT 0x,   CONSTRAINT PK_T2 PRIMARY KEY CLUSTERED (TID, Column1) ON PST (TID) ); The next script loads 5 million rows into T1 with a pseudo-random value between 1 and 5 for Column1. The table is partitioned on the IDENTITY column TID: INSERT dbo.T1 WITH (TABLOCKX) (Column1) SELECT (ABS(CHECKSUM(NEWID())) % 5) + 1 FROM dbo.Numbers AS N WHERE n BETWEEN 1 AND 5000000; In case you don’t already have an auxiliary table of numbers lying around, here’s a script to create one with 10 million rows: CREATE TABLE dbo.Numbers (n bigint PRIMARY KEY);   WITH L0 AS(SELECT 1 AS c UNION ALL SELECT 1), L1 AS(SELECT 1 AS c FROM L0 AS A CROSS JOIN L0 AS B), L2 AS(SELECT 1 AS c FROM L1 AS A CROSS JOIN L1 AS B), L3 AS(SELECT 1 AS c FROM L2 AS A CROSS JOIN L2 AS B), L4 AS(SELECT 1 AS c FROM L3 AS A CROSS JOIN L3 AS B), L5 AS(SELECT 1 AS c FROM L4 AS A CROSS JOIN L4 AS B), Nums AS(SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS n FROM L5) INSERT dbo.Numbers WITH (TABLOCKX) SELECT TOP (10000000) n FROM Nums ORDER BY n OPTION (MAXDOP 1); Table T1 contains data like this: Next we load data into table T2. The relationship between the two tables is that table 2 contains ‘n’ rows for each row in table 1, where ‘n’ is determined by the value in Column1 of table T1. There is nothing particularly special about the data or distribution, by the way. INSERT dbo.T2 WITH (TABLOCKX) (TID, Column1) SELECT T.TID, N.n FROM dbo.T1 AS T JOIN dbo.Numbers AS N ON N.n >= 1 AND N.n <= T.Column1; Table T2 ends up containing about 15 million rows: The primary key for table T2 is a combination of TID and Column1. The data is partitioned according to the value in column TID alone. Partition Distribution The following query shows the number of rows in each partition of table T1: SELECT PartitionID = CA1.P, NumRows = COUNT_BIG(*) FROM dbo.T1 AS T CROSS APPLY (VALUES ($PARTITION.PFT(TID))) AS CA1 (P) GROUP BY CA1.P ORDER BY CA1.P; There are 40 partitions containing 125,000 rows (40 * 125k = 5m rows). The rightmost partition remains empty. The next query shows the distribution for table 2: SELECT PartitionID = CA1.P, NumRows = COUNT_BIG(*) FROM dbo.T2 AS T CROSS APPLY (VALUES ($PARTITION.PFT(TID))) AS CA1 (P) GROUP BY CA1.P ORDER BY CA1.P; There are roughly 375,000 rows in each partition (the rightmost partition is also empty): Ok, that’s the test data done. Test Query and Execution Plan The task is to count the rows resulting from joining tables 1 and 2 on the TID column: SET STATISTICS IO ON; DECLARE @s datetime2 = SYSUTCDATETIME();   SELECT COUNT_BIG(*) FROM dbo.T1 AS T1 JOIN dbo.T2 AS T2 ON T2.TID = T1.TID;   SELECT DATEDIFF(Millisecond, @s, SYSUTCDATETIME()); SET STATISTICS IO OFF; The optimizer chooses a plan using parallel hash join, and partial aggregation: The Plan Explorer plan tree view shows accurate cardinality estimates and an even distribution of rows across threads (click to enlarge the image): With a warm data cache, the STATISTICS IO output shows that no physical I/O was needed, and all 41 partitions were touched: Running the query without actual execution plan or STATISTICS IO information for maximum performance, the query returns in around 2600ms. Execution Plan Analysis The first step toward improving on the execution plan produced by the query optimizer is to understand how it works, at least in outline. The two parallel Clustered Index Scans use multiple threads to read rows from tables T1 and T2. Parallel scan uses a demand-based scheme where threads are given page(s) to scan from the table as needed. This arrangement has certain important advantages, but does result in an unpredictable distribution of rows amongst threads. The point is that multiple threads cooperate to scan the whole table, but it is impossible to predict which rows end up on which threads. For correct results from the parallel hash join, the execution plan has to ensure that rows from T1 and T2 that might join are processed on the same thread. For example, if a row from T1 with join key value ‘1234’ is placed in thread 5’s hash table, the execution plan must guarantee that any rows from T2 that also have join key value ‘1234’ probe thread 5’s hash table for matches. The way this guarantee is enforced in this parallel hash join plan is by repartitioning rows to threads after each parallel scan. The two repartitioning exchanges route rows to threads using a hash function over the hash join keys. The two repartitioning exchanges use the same hash function so rows from T1 and T2 with the same join key must end up on the same hash join thread. Expensive Exchanges This business of repartitioning rows between threads can be very expensive, especially if a large number of rows is involved. The execution plan selected by the optimizer moves 5 million rows through one repartitioning exchange and around 15 million across the other. As a first step toward removing these exchanges, consider the execution plan selected by the optimizer if we join just one partition from each table, disallowing parallelism: SELECT COUNT_BIG(*) FROM dbo.T1 AS T1 JOIN dbo.T2 AS T2 ON T2.TID = T1.TID WHERE $PARTITION.PFT(T1.TID) = 1 AND $PARTITION.PFT(T2.TID) = 1 OPTION (MAXDOP 1); The optimizer has chosen a (one-to-many) merge join instead of a hash join. The single-partition query completes in around 100ms. If everything scaled linearly, we would expect that extending this strategy to all 40 populated partitions would result in an execution time around 4000ms. Using parallelism could reduce that further, perhaps to be competitive with the parallel hash join chosen by the optimizer. This raises a question. If the most efficient way to join one partition from each of the tables is to use a merge join, why does the optimizer not choose a merge join for the full query? Forcing a Merge Join Let’s force the optimizer to use a merge join on the test query using a hint: SELECT COUNT_BIG(*) FROM dbo.T1 AS T1 JOIN dbo.T2 AS T2 ON T2.TID = T1.TID OPTION (MERGE JOIN); This is the execution plan selected by the optimizer: This plan results in the same number of logical reads reported previously, but instead of 2600ms the query takes 5000ms. The natural explanation for this drop in performance is that the merge join plan is only using a single thread, whereas the parallel hash join plan could use multiple threads. Parallel Merge Join We can get a parallel merge join plan using the same query hint as before, and adding trace flag 8649: SELECT COUNT_BIG(*) FROM dbo.T1 AS T1 JOIN dbo.T2 AS T2 ON T2.TID = T1.TID OPTION (MERGE JOIN, QUERYTRACEON 8649); The execution plan is: This looks promising. It uses a similar strategy to distribute work across threads as seen for the parallel hash join. In practice though, performance is disappointing. On a typical run, the parallel merge plan runs for around 8400ms; slower than the single-threaded merge join plan (5000ms) and much worse than the 2600ms for the parallel hash join. We seem to be going backwards! The logical reads for the parallel merge are still exactly the same as before, with no physical IOs. The cardinality estimates and thread distribution are also still very good (click to enlarge): A big clue to the reason for the poor performance is shown in the wait statistics (captured by Plan Explorer Pro): CXPACKET waits require careful interpretation, and are most often benign, but in this case excessive waiting occurs at the repartitioning exchanges. Unlike the parallel hash join, the repartitioning exchanges in this plan are order-preserving ‘merging’ exchanges (because merge join requires ordered inputs): Parallelism works best when threads can just grab any available unit of work and get on with processing it. Preserving order introduces inter-thread dependencies that can easily lead to significant waits occurring. In extreme cases, these dependencies can result in an intra-query deadlock, though the details of that will have to wait for another time to explore in detail. The potential for waits and deadlocks leads the query optimizer to cost parallel merge join relatively highly, especially as the degree of parallelism (DOP) increases. This high costing resulted in the optimizer choosing a serial merge join rather than parallel in this case. The test results certainly confirm its reasoning. Collocated Joins In SQL Server 2008 and later, the optimizer has another available strategy when joining tables that share a common partition scheme. This strategy is a collocated join, also known as as a per-partition join. It can be applied in both serial and parallel execution plans, though it is limited to 2-way joins in the current optimizer. Whether the optimizer chooses a collocated join or not depends on cost estimation. The primary benefits of a collocated join are that it eliminates an exchange and requires less memory, as we will see next. Costing and Plan Selection The query optimizer did consider a collocated join for our original query, but it was rejected on cost grounds. The parallel hash join with repartitioning exchanges appeared to be a cheaper option. There is no query hint to force a collocated join, so we have to mess with the costing framework to produce one for our test query. Pretending that IOs cost 50 times more than usual is enough to convince the optimizer to use collocated join with our test query: -- Pretend IOs are 50x cost temporarily DBCC SETIOWEIGHT(50);   -- Co-located hash join SELECT COUNT_BIG(*) FROM dbo.T1 AS T1 JOIN dbo.T2 AS T2 ON T2.TID = T1.TID OPTION (RECOMPILE);   -- Reset IO costing DBCC SETIOWEIGHT(1); Collocated Join Plan The estimated execution plan for the collocated join is: The Constant Scan contains one row for each partition of the shared partitioning scheme, from 1 to 41. The hash repartitioning exchanges seen previously are replaced by a single Distribute Streams exchange using Demand partitioning. Demand partitioning means that the next partition id is given to the next parallel thread that asks for one. My test machine has eight logical processors, and all are available for SQL Server to use. As a result, there are eight threads in the single parallel branch in this plan, each processing one partition from each table at a time. Once a thread finishes processing a partition, it grabs a new partition number from the Distribute Streams exchange…and so on until all partitions have been processed. It is important to understand that the parallel scans in this plan are different from the parallel hash join plan. Although the scans have the same parallelism icon, tables T1 and T2 are not being co-operatively scanned by multiple threads in the same way. Each thread reads a single partition of T1 and performs a hash match join with the same partition from table T2. The properties of the two Clustered Index Scans show a Seek Predicate (unusual for a scan!) limiting the rows to a single partition: The crucial point is that the join between T1 and T2 is on TID, and TID is the partitioning column for both tables. A thread that processes partition ‘n’ is guaranteed to see all rows that can possibly join on TID for that partition. In addition, no other thread will see rows from that partition, so this removes the need for repartitioning exchanges. CPU and Memory Efficiency Improvements The collocated join has removed two expensive repartitioning exchanges and added a single exchange processing 41 rows (one for each partition id). Remember, the parallel hash join plan exchanges had to process 5 million and 15 million rows. The amount of processor time spent on exchanges will be much lower in the collocated join plan. In addition, the collocated join plan has a maximum of 8 threads processing single partitions at any one time. The 41 partitions will all be processed eventually, but a new partition is not started until a thread asks for it. Threads can reuse hash table memory for the new partition. The parallel hash join plan also had 8 hash tables, but with all 5,000,000 build rows loaded at the same time. The collocated plan needs memory for only 8 * 125,000 = 1,000,000 rows at any one time. Collocated Hash Join Performance The collated join plan has disappointing performance in this case. The query runs for around 25,300ms despite the same IO statistics as usual. This is much the worst result so far, so what went wrong? It turns out that cardinality estimation for the single partition scans of table T1 is slightly low. The properties of the Clustered Index Scan of T1 (graphic immediately above) show the estimation was for 121,951 rows. This is a small shortfall compared with the 125,000 rows actually encountered, but it was enough to cause the hash join to spill to physical tempdb: A level 1 spill doesn’t sound too bad, until you realize that the spill to tempdb probably occurs for each of the 41 partitions. As a side note, the cardinality estimation error is a little surprising because the system tables accurately show there are 125,000 rows in every partition of T1. Unfortunately, the optimizer uses regular column and index statistics to derive cardinality estimates here rather than system table information (e.g. sys.partitions). Collocated Merge Join We will never know how well the collocated parallel hash join plan might have worked without the cardinality estimation error (and the resulting 41 spills to tempdb) but we do know: Merge join does not require a memory grant; and Merge join was the optimizer’s preferred join option for a single partition join Putting this all together, what we would really like to see is the same collocated join strategy, but using merge join instead of hash join. Unfortunately, the current query optimizer cannot produce a collocated merge join; it only knows how to do collocated hash join. So where does this leave us? CROSS APPLY sys.partitions We can try to write our own collocated join query. We can use sys.partitions to find the partition numbers, and CROSS APPLY to get a count per partition, with a final step to sum the partial counts. The following query implements this idea: SELECT row_count = SUM(Subtotals.cnt) FROM ( -- Partition numbers SELECT p.partition_number FROM sys.partitions AS p WHERE p.[object_id] = OBJECT_ID(N'T1', N'U') AND p.index_id = 1 ) AS P CROSS APPLY ( -- Count per collocated join SELECT cnt = COUNT_BIG(*) FROM dbo.T1 AS T1 JOIN dbo.T2 AS T2 ON T2.TID = T1.TID WHERE $PARTITION.PFT(T1.TID) = p.partition_number AND $PARTITION.PFT(T2.TID) = p.partition_number ) AS SubTotals; The estimated plan is: The cardinality estimates aren’t all that good here, especially the estimate for the scan of the system table underlying the sys.partitions view. Nevertheless, the plan shape is heading toward where we would like to be. Each partition number from the system table results in a per-partition scan of T1 and T2, a one-to-many Merge Join, and a Stream Aggregate to compute the partial counts. The final Stream Aggregate just sums the partial counts. Execution time for this query is around 3,500ms, with the same IO statistics as always. This compares favourably with 5,000ms for the serial plan produced by the optimizer with the OPTION (MERGE JOIN) hint. This is another case of the sum of the parts being less than the whole – summing 41 partial counts from 41 single-partition merge joins is faster than a single merge join and count over all partitions. Even so, this single-threaded collocated merge join is not as quick as the original parallel hash join plan, which executed in 2,600ms. On the positive side, our collocated merge join uses only one logical processor and requires no memory grant. The parallel hash join plan used 16 threads and reserved 569 MB of memory:   Using a Temporary Table Our collocated merge join plan should benefit from parallelism. The reason parallelism is not being used is that the query references a system table. We can work around that by writing the partition numbers to a temporary table (or table variable): SET STATISTICS IO ON; DECLARE @s datetime2 = SYSUTCDATETIME();   CREATE TABLE #P ( partition_number integer PRIMARY KEY);   INSERT #P (partition_number) SELECT p.partition_number FROM sys.partitions AS p WHERE p.[object_id] = OBJECT_ID(N'T1', N'U') AND p.index_id = 1;   SELECT row_count = SUM(Subtotals.cnt) FROM #P AS p CROSS APPLY ( SELECT cnt = COUNT_BIG(*) FROM dbo.T1 AS T1 JOIN dbo.T2 AS T2 ON T2.TID = T1.TID WHERE $PARTITION.PFT(T1.TID) = p.partition_number AND $PARTITION.PFT(T2.TID) = p.partition_number ) AS SubTotals;   DROP TABLE #P;   SELECT DATEDIFF(Millisecond, @s, SYSUTCDATETIME()); SET STATISTICS IO OFF; Using the temporary table adds a few logical reads, but the overall execution time is still around 3500ms, indistinguishable from the same query without the temporary table. The problem is that the query optimizer still doesn’t choose a parallel plan for this query, though the removal of the system table reference means that it could if it chose to: In fact the optimizer did enter the parallel plan phase of query optimization (running search 1 for a second time): Unfortunately, the parallel plan found seemed to be more expensive than the serial plan. This is a crazy result, caused by the optimizer’s cost model not reducing operator CPU costs on the inner side of a nested loops join. Don’t get me started on that, we’ll be here all night. In this plan, everything expensive happens on the inner side of a nested loops join. Without a CPU cost reduction to compensate for the added cost of exchange operators, candidate parallel plans always look more expensive to the optimizer than the equivalent serial plan. Parallel Collocated Merge Join We can produce the desired parallel plan using trace flag 8649 again: SELECT row_count = SUM(Subtotals.cnt) FROM #P AS p CROSS APPLY ( SELECT cnt = COUNT_BIG(*) FROM dbo.T1 AS T1 JOIN dbo.T2 AS T2 ON T2.TID = T1.TID WHERE $PARTITION.PFT(T1.TID) = p.partition_number AND $PARTITION.PFT(T2.TID) = p.partition_number ) AS SubTotals OPTION (QUERYTRACEON 8649); The actual execution plan is: One difference between this plan and the collocated hash join plan is that a Repartition Streams exchange operator is used instead of Distribute Streams. The effect is similar, though not quite identical. The Repartition uses round-robin partitioning, meaning the next partition id is pushed to the next thread in sequence. The Distribute Streams exchange seen earlier used Demand partitioning, meaning the next partition id is pulled across the exchange by the next thread that is ready for more work. There are subtle performance implications for each partitioning option, but going into that would again take us too far off the main point of this post. Performance The important thing is the performance of this parallel collocated merge join – just 1350ms on a typical run. The list below shows all the alternatives from this post (all timings include creation, population, and deletion of the temporary table where appropriate) from quickest to slowest: Collocated parallel merge join: 1350ms Parallel hash join: 2600ms Collocated serial merge join: 3500ms Serial merge join: 5000ms Parallel merge join: 8400ms Collated parallel hash join: 25,300ms (hash spill per partition) The parallel collocated merge join requires no memory grant (aside from a paltry 1.2MB used for exchange buffers). This plan uses 16 threads at DOP 8; but 8 of those are (rather pointlessly) allocated to the parallel scan of the temporary table. These are minor concerns, but it turns out there is a way to address them if it bothers you. Parallel Collocated Merge Join with Demand Partitioning This final tweak replaces the temporary table with a hard-coded list of partition ids (dynamic SQL could be used to generate this query from sys.partitions): SELECT row_count = SUM(Subtotals.cnt) FROM ( VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10), (11),(12),(13),(14),(15),(16),(17),(18),(19),(20), (21),(22),(23),(24),(25),(26),(27),(28),(29),(30), (31),(32),(33),(34),(35),(36),(37),(38),(39),(40),(41) ) AS P (partition_number) CROSS APPLY ( SELECT cnt = COUNT_BIG(*) FROM dbo.T1 AS T1 JOIN dbo.T2 AS T2 ON T2.TID = T1.TID WHERE $PARTITION.PFT(T1.TID) = p.partition_number AND $PARTITION.PFT(T2.TID) = p.partition_number ) AS SubTotals OPTION (QUERYTRACEON 8649); The actual execution plan is: The parallel collocated hash join plan is reproduced below for comparison: The manual rewrite has another advantage that has not been mentioned so far: the partial counts (per partition) can be computed earlier than the partial counts (per thread) in the optimizer’s collocated join plan. The earlier aggregation is performed by the extra Stream Aggregate under the nested loops join. The performance of the parallel collocated merge join is unchanged at around 1350ms. Final Words It is a shame that the current query optimizer does not consider a collocated merge join (Connect item closed as Won’t Fix). The example used in this post showed an improvement in execution time from 2600ms to 1350ms using a modestly-sized data set and limited parallelism. In addition, the memory requirement for the query was almost completely eliminated  – down from 569MB to 1.2MB. The problem with the parallel hash join selected by the optimizer is that it attempts to process the full data set all at once (albeit using eight threads). It requires a large memory grant to hold all 5 million rows from table T1 across the eight hash tables, and does not take advantage of the divide-and-conquer opportunity offered by the common partitioning. The great thing about the collocated join strategies is that each parallel thread works on a single partition from both tables, reading rows, performing the join, and computing a per-partition subtotal, before moving on to a new partition. From a thread’s point of view… If you have trouble visualizing what is happening from just looking at the parallel collocated merge join execution plan, let’s look at it again, but from the point of view of just one thread operating between the two Parallelism (exchange) operators. Our thread picks up a single partition id from the Distribute Streams exchange, and starts a merge join using ordered rows from partition 1 of table T1 and partition 1 of table T2. By definition, this is all happening on a single thread. As rows join, they are added to a (per-partition) count in the Stream Aggregate immediately above the Merge Join. Eventually, either T1 (partition 1) or T2 (partition 1) runs out of rows and the merge join stops. The per-partition count from the aggregate passes on through the Nested Loops join to another Stream Aggregate, which is maintaining a per-thread subtotal. Our same thread now picks up a new partition id from the exchange (say it gets id 9 this time). The count in the per-partition aggregate is reset to zero, and the processing of partition 9 of both tables proceeds just as it did for partition 1, and on the same thread. Each thread picks up a single partition id and processes all the data for that partition, completely independently from other threads working on other partitions. One thread might eventually process partitions (1, 9, 17, 25, 33, 41) while another is concurrently processing partitions (2, 10, 18, 26, 34) and so on for the other six threads at DOP 8. The point is that all 8 threads can execute independently and concurrently, continuing to process new partitions until the wider job (of which the thread has no knowledge!) is done. This divide-and-conquer technique can be much more efficient than simply splitting the entire workload across eight threads all at once. Related Reading Understanding and Using Parallelism in SQL Server Parallel Execution Plans Suck © 2013 Paul White – All Rights Reserved Twitter: @SQL_Kiwi

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  • Rounded Corners and Shadows &ndash; Dialogs with CSS

    - by Rick Strahl
    Well, it looks like we’ve finally arrived at a place where at least all of the latest versions of main stream browsers support rounded corners and box shadows. The two CSS properties that make this possible are box-shadow and box-radius. Both of these CSS Properties now supported in all the major browsers as shown in this chart from QuirksMode: In it’s simplest form you can use box-shadow and border radius like this: .boxshadow { -moz-box-shadow: 3px 3px 5px #535353; -webkit-box-shadow: 3px 3px 5px #535353; box-shadow: 3px 3px 5px #535353; } .roundbox { -moz-border-radius: 6px 6px 6px 6px; -webkit-border-radius: 6px; border-radius: 6px 6px 6px 6px; } box-shadow: horizontal-shadow-pixels vertical-shadow-pixels blur-distance shadow-color box-shadow attributes specify the the horizontal and vertical offset of the shadow, the blur distance (to give the shadow a smooth soft look) and a shadow color. The spec also supports multiple shadows separated by commas using the attributes above but we’re not using that functionality here. box-radius: top-left-radius top-right-radius bottom-right-radius bottom-left-radius border-radius takes a pixel size for the radius for each corner going clockwise. CSS 3 also specifies each of the individual corner elements such as border-top-left-radius, but support for these is much less prevalent so I would recommend not using them for now until support improves. Instead use the single box-radius to specify all corners. Browser specific Support in older Browsers Notice that there are two variations: The actual CSS 3 properties (box-shadow and box-radius) and the browser specific ones (-moz, –webkit prefixes for FireFox and Chrome/Safari respectively) which work in slightly older versions of modern browsers before official CSS 3 support was added. The goal is to spread support as widely as possible and the prefix versions extend the range slightly more to those browsers that provided early support for these features. Notice that box-shadow and border-radius are used after the browser specific versions to ensure that the latter versions get precedence if the browser supports both (last assignment wins). Use the .boxshadow and .roundbox Styles in HTML To use these two styles create a simple rounded box with a shadow you can use HTML like this: <!-- Simple Box with rounded corners and shadow --> <div class="roundbox boxshadow" style="width: 550px; border: solid 2px steelblue"> <div class="boxcontenttext"> Simple Rounded Corner Box. </div> </div> which looks like this in the browser: This works across browsers and it’s pretty sweet and simple. Watch out for nested Elements! There are a couple of things to be aware of however when using rounded corners. Specifically, you need to be careful when you nest other non-transparent content into the rounded box. For example check out what happens when I change the inside <div> to have a colored background: <!-- Simple Box with rounded corners and shadow --> <div class="roundbox boxshadow" style="width: 550px; border: solid 2px steelblue"> <div class="boxcontenttext" style="background: khaki;"> Simple Rounded Corner Box. </div> </div> which renders like this:   If you look closely you’ll find that the inside <div>’s corners are not rounded and so ‘poke out’ slightly over the rounded corners. It looks like the rounded corners are ‘broken’ up instead of a solid rounded line around the corner, which his pretty ugly. The bigger the radius the more drastic this effect becomes . To fix this issue the inner <div> also has have rounded corners at the same or slightly smaller radius than the outer <div>. The simple fix for this is to simply also apply the roundbox style to the inner <div> in addition to the boxcontenttext style already applied: <div class="boxcontenttext roundbox" style="background: khaki;"> The fixed display now looks proper: Separate Top and Bottom Elements This gets even a little more tricky if you have an element at the top or bottom only of the rounded box. What if you need to add something like a header or footer <div> that have non-transparent backgrounds which is a pretty common scenario? In those cases you want only the top or bottom corners rounded and not both. To make this work a couple of additional styles to round only the top and bottom corners can be created: .roundbox-top { -moz-border-radius: 4px 4px 0 0; -webkit-border-radius: 4px 4px 0 0; border-radius: 4px 4px 0 0; } .roundbox-bottom { -moz-border-radius: 0 0 4px 4px; -webkit-border-radius: 0 0 4px 4px; border-radius: 0 0 4px 4px; } Notice that radius used for the ‘inside’ rounding is smaller (4px) than the outside radius (6px). This is so the inner radius fills into the outer border – if you use the same size you may have some white space showing between inner and out rounded corners. Experiment with values to see what works – in my experimenting the behavior across browsers here is consistent (thankfully). These styles can be applied in addition to other styles to make only the top or bottom portions of an element rounded. For example imagine I have styles like this: .gridheader, .gridheaderbig, .gridheaderleft, .gridheaderright { padding: 4px 4px 4px 4px; background: #003399 url(images/vertgradient.png) repeat-x; text-align: center; font-weight: bold; text-decoration: none; color: khaki; } .gridheaderleft { text-align: left; } .gridheaderright { text-align: right; } .gridheaderbig { font-size: 135%; } If I just apply say gridheader by itself in HTML like this: <div class="roundbox boxshadow" style="width: 550px; border: solid 2px steelblue"> <div class="gridheaderleft">Box with a Header</div> <div class="boxcontenttext" style="background: khaki;"> Simple Rounded Corner Box. </div> </div> This results in a pretty funky display – again due to the fact that the inner elements render square rather than rounded corners: If you look close again you can see that both the header and the main content have square edges which jumps out at the eye. To fix this you can now apply the roundbox-top and roundbox-bottom to the header and content respectively: <div class="roundbox boxshadow" style="width: 550px; border: solid 2px steelblue"> <div class="gridheaderleft roundbox-top">Box with a Header</div> <div class="boxcontenttext roundbox-bottom" style="background: khaki;"> Simple Rounded Corner Box. </div> </div> Which now gives the proper display with rounded corners both on the top and bottom: All of this is sweet to be supported – at least by the newest browser – without having to resort to images and nasty JavaScripts solutions. While this is still not a mainstream feature yet for the majority of actually installed browsers, the majority of browser users are very likely to have this support as most browsers other than IE are actively pushing users to upgrade to newer versions. Since this is a ‘visual display only feature it degrades reasonably well in non-supporting browsers: You get an uninteresting square and non-shadowed browser box, but the display is still overall functional. The main sticking point – as always is Internet Explorer versions 8.0 and down as well as older versions of other browsers. With those browsers you get a functional view that is a little less interesting to look at obviously: but at least it’s still functional. Maybe that’s just one more incentive for people using older browsers to upgrade to a  more modern browser :-) Creating Dialog Related Styles In a lot of my AJAX based applications I use pop up windows which effectively work like dialogs. Using the simple CSS behaviors above, it’s really easy to create some fairly nice looking overlaid windows with nothing but CSS. Here’s what a typical ‘dialog’ I use looks like: The beauty of this is that it’s plain CSS – no plug-ins or images (other than the gradients which are optional) required. Add jQuery-ui draggable (or ww.jquery.js as shown below) and you have a nice simple inline implementation of a dialog represented by a simple <div> tag. Here’s the HTML for this dialog: <div id="divDialog" class="dialog boxshadow" style="width: 450px;"> <div class="dialog-header"> <div class="closebox"></div> User Sign-in </div> <div class="dialog-content"> <label>Username:</label> <input type="text" name="txtUsername" value=" " /> <label>Password</label> <input type="text" name="txtPassword" value=" " /> <hr /> <input type="button" id="btnLogin" value="Login" /> </div> <div class="dialog-statusbar">Ready</div> </div> Most of this behavior is driven by the ‘dialog’ styles which are fairly basic and easy to understand. They do use a few support images for the gradients which are provided in the sample I’ve provided. Here’s what the CSS looks like: .dialog { background: White; overflow: hidden; border: solid 1px steelblue; -moz-border-radius: 6px 6px 4px 4px; -webkit-border-radius: 6px 6px 4px 4px; border-radius: 6px 6px 3px 3px; } .dialog-header { background-image: url(images/dialogheader.png); background-repeat: repeat-x; text-align: left; color: cornsilk; padding: 5px; padding-left: 10px; font-size: 1.02em; font-weight: bold; position: relative; -moz-border-radius: 4px 4px 0px 0px; -webkit-border-radius: 4px 4px 0px 0px; border-radius: 4px 4px 0px 0px; } .dialog-top { -moz-border-radius: 4px 4px 0px 0px; -webkit-border-radius: 4px 4px 0px 0px; border-radius: 4px 4px 0px 0px; } .dialog-bottom { -moz-border-radius: 0 0 3px 3px; -webkit-border-radius: 0 0 3px 3px; border-radius: 0 0 3px 3px; } .dialog-content { padding: 15px; } .dialog-statusbar, .dialog-toolbar { background: #eeeeee; background-image: url(images/dialogstrip.png); background-repeat: repeat-x; padding: 5px; padding-left: 10px; border-top: solid 1px silver; border-bottom: solid 1px silver; font-size: 0.8em; } .dialog-statusbar { -moz-border-radius: 0 0 3px 3px; -webkit-border-radius: 0 0 3px 3px; border-radius: 0 0 3px 3px; padding-right: 10px; } .closebox { position: absolute; right: 2px; top: 2px; background-image: url(images/close.gif); background-repeat: no-repeat; width: 14px; height: 14px; cursor: pointer; opacity: 0.60; filter: alpha(opacity="80"); } .closebox:hover { opacity: 1; filter: alpha(opacity="100"); } The main style is the dialog class which is the outer box. It has the rounded border that serves as the outline. Note that I didn’t add the box-shadow to this style because in some situations I just want the rounded box in an inline display that doesn’t have a shadow so it’s still applied separately. dialog-header, then has the rounded top corners and displays a typical dialog heading format. dialog-bottom and dialog-top then provide the same functionality as roundbox-top and roundbox-bottom described earlier but are provided mainly in the stylesheet for consistency to match the dialog’s round edges and making it easier to  remember and find in Intellisense as it shows up in the same dialog- group. dialog-statusbar and dialog-toolbar are two elements I use a lot for floating windows – the toolbar serves for buttons and options and filters typically, while the status bar provides information specific to the floating window. Since the the status bar is always on the bottom of the dialog it automatically handles the rounding of the bottom corners. Finally there’s  closebox style which is to be applied to an empty <div> tag in the header typically. What this does is render a close image that is by default low-lighted with a low opacity value, and then highlights when hovered over. All you’d have to do handle the close operation is handle the onclick of the <div>. Note that the <div> right aligns so typically you should specify it before any other content in the header. Speaking of closable – some time ago I created a closable jQuery plug-in that basically automates this process and can be applied against ANY element in a page, automatically removing or closing the element with some simple script code. Using this you can leave out the <div> tag for closable and just do the following: To make the above dialog closable (and draggable) which makes it effectively and overlay window, you’d add jQuery.js and ww.jquery.js to the page: <script type="text/javascript" src="../../scripts/jquery.min.js"></script> <script type="text/javascript" src="../../scripts/ww.jquery.min.js"></script> and then simply call: <script type="text/javascript"> $(document).ready(function () { $("#divDialog") .draggable({ handle: ".dialog-header" }) .closable({ handle: ".dialog-header", closeHandler: function () { alert("Window about to be closed."); return true; // true closes - false leaves open } }); }); </script> * ww.jquery.js emulates base features in jQuery-ui’s draggable. If jQuery-ui is loaded its draggable version will be used instead and voila you have now have a draggable and closable window – here in mid-drag:   The dragging and closable behaviors are of course optional, but it’s the final touch that provides dialog like window behavior. Relief for older Internet Explorer Versions with CSS Pie If you want to get these features to work with older versions of Internet Explorer all the way back to version 6 you can check out CSS Pie. CSS Pie provides an Internet Explorer behavior file that attaches to specific CSS rules and simulates these behavior using script code in IE (mostly by implementing filters). You can simply add the behavior to each CSS style that uses box-shadow and border-radius like this: .boxshadow {     -moz-box-shadow: 3px 3px 5px #535353;     -webkit-box-shadow: 3px 3px 5px #535353;           box-shadow: 3px 3px 5px #535353;     behavior: url(scripts/PIE.htc);           } .roundbox {      -moz-border-radius: 6px 6px 6px 6px;     -webkit-border-radius: 6px;      border-radius: 6px 6px 6px 6px;     behavior: url(scripts/PIE.htc); } CSS Pie requires the PIE.htc on your server and referenced from each CSS style that needs it. Note that the url() for IE behaviors is NOT CSS file relative as other CSS resources, but rather PAGE relative , so if you have more than one folder you probably need to reference the HTC file with a fixed path like this: behavior: url(/MyApp/scripts/PIE.htc); in the style. Small price to pay, but a royal pain if you have a common CSS file you use in many applications. Once the PIE.htc file has been copied and you have applied the behavior to each style that uses these new features Internet Explorer will render rounded corners and box shadows! Yay! Hurray for box-shadow and border-radius All of this functionality is very welcome natively in the browser. If you think this is all frivolous visual candy, you might be right :-), but if you take a look on the Web and search for rounded corner solutions that predate these CSS attributes you’ll find a boatload of stuff from image files, to custom drawn content to Javascript solutions that play tricks with a few images. It’s sooooo much easier to have this functionality built in and I for one am glad to see that’s it’s finally becoming standard in the box. Still remember that when you use these new CSS features, they are not universal, and are not going to be really soon. Legacy browsers, especially old versions of Internet Explorer that can’t be updated will continue to be around and won’t work with this shiny new stuff. I say screw ‘em: Let them get a decent recent browser or see a degraded and ugly UI. We have the luxury with this functionality in that it doesn’t typically affect usability – it just doesn’t look as nice. Resources Download the Sample The sample includes the styles and images and sample page as well as ww.jquery.js for the draggable/closable example. Online Sample Check out the sample described in this post online. Closable and Draggable Documentation Documentation for the closeable and draggable plug-ins in ww.jquery.js. You can also check out the full documentation for all the plug-ins contained in ww.jquery.js here. © Rick Strahl, West Wind Technologies, 2005-2011Posted in HTML  CSS  

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  • What Every Developer Should Know About MSI Components

    - by Alois Kraus
    Hopefully nothing. But if you have to do more than simple XCopy deployment and you need to support updates, upgrades and perhaps side by side scenarios there is no way around MSI. You can create Msi files with a Visual Studio Setup project which is severely limited or you can use the Windows Installer Toolset. I cannot talk about WIX with my German colleagues because WIX has a very special meaning. It is funny to always use the long name when I talk about deployment possibilities. Alternatively you can buy commercial tools which help you to author Msi files but I am not sure how good they are. Given enough pain with existing solutions you can also learn the MSI Apis and create your own packaging solution. If I were you I would use either a commercial visual tool when you do easy deployments or use the free Windows Installer Toolset. Once you know the WIX schema you can create well formed wix xml files easily with any editor. Then you can “compile” from the wxs files your Msi package. Recently I had the “pleasure” to get my hands dirty with C++ (again) and the MSI technology. Installation is a complex topic but after several month of digging into arcane MSI issues I can safely say that there should exist an easier way to install and update files as today. I am not alone with this statement as John Robbins (creator of the cool tool Paraffin) states: “.. It's a brittle and scary API in Windows …”. To help other people struggling with installation issues I present you the advice I (and others) found useful and what will happen if you ignore this advice. What is a MSI file? A MSI file is basically a database with tables which reference each other to control how your un/installation should work. The basic idea is that you declare via these tables what you want to install and MSI controls the how to get your stuff onto or off your machine. Your “stuff” consists usually of files, registry keys, shortcuts and environment variables. Therefore the most important tables are File, Registry, Environment and Shortcut table which define what will be un/installed. The key to master MSI is that every resource (file, registry key ,…) is associated with a MSI component. The actual payload consists of compressed files in the CAB format which can either be embedded into the MSI file or reside beside the MSI file or in a subdirectory below it. To examine MSI files you need Orca a free MSI editor provided by MS. There is also another free editor called Super Orca which does support diffs between MSI and it does not lock the MSI files. But since Orca comes with a shell extension I tend to use only Orca because it is so easy to right click on a MSI file and open it with this tool. How Do I Install It? Double click it. This does work for fresh installations as well as major upgrades. Updates need to be installed via the command line via msiexec /i <msi> REINSTALL=ALL REINSTALLMODE=vomus   This tells the installer to reinstall all already installed features (new features will NOT be installed). The reinstallmode letters do force an overwrite of the old cached package in the %WINDIR%\Installer folder. All files, shortcuts and registry keys are redeployed if they are missing or need to be replaced with a newer version. When things did go really wrong and you want to overwrite everything unconditionally use REINSTALLMODE=vamus. How To Enable MSI Logs? You can download a MSI from Microsoft which installs some registry keys to enable full MSI logging. The log files can be found in your %TEMP% folder and are called MSIxxxx.log. Alternatively you can add to your msiexec command line the option msiexec …. /l*vx <LogFileName> Personally I find it rather strange that * does not mean full logging. To really get all logs I need to add v and x which is documented in the msiexec help but I still find this behavior unintuitive. What are MSI components? The whole MSI logic is bound to the concept of MSI components. Nearly every msi table has a Component column which binds an installable resource to a component. Below are the screenshots of the FeatureComponents and Component table of an example MSI. The Feature table defines basically the feature hierarchy.  To find out what belongs to a feature you need to look at the FeatureComponents table where for each feature the components are listed which will be installed when a feature is installed. The MSI components are defined in the  Component table. This table has as first column the component name and as second column the component id which is a GUID. All resources you want to install belong to a MSI component. Therefore nearly all MSI tables have a Component_ column which contains the component name. If you look e.g. a the File table you see that every file belongs to a component which is true for all other tables which install resources. The component table is the glue between all other tables which contain the resources you want to install. So far so easy. Why is MSI then so complex? Most MSI problems arise from the fact that you did violate a MSI component rule in one or the other way. When you install a feature the reference count for all components belonging to this feature will increase by one. If your component is installed by more than one feature it will get a higher refcount. When you uninstall a feature its refcount will drop by one. Interesting things happen if the component reference count reaches zero: Then all associated resources will be deleted. That looks like a reasonable thing and it is. What it makes complex are the strange component rules you have to follow. Below are some important component rules from the Tao of the Windows Installer … Rule 16: Follow Component Rules Components are a very important part of the Installer technology. They are the means whereby the Installer manages the resources that make up your application. The SDK provides the following guidelines for creating components in your package: Never create two components that install a resource under the same name and target location. If a resource must be duplicated in multiple components, change its name or target location in each component. This rule should be applied across applications, products, product versions, and companies. Two components must not have the same key path file. This is a consequence of the previous rule. The key path value points to a particular file or folder belonging to the component that the installer uses to detect the component. If two components had the same key path file, the installer would be unable to distinguish which component is installed. Two components however may share a key path folder. Do not create a version of a component that is incompatible with all previous versions of the component. This rule should be applied across applications, products, product versions, and companies. Do not create components containing resources that will need to be installed into more than one directory on the user’s system. The installer installs all of the resources in a component into the same directory. It is not possible to install some resources into subdirectories. Do not include more than one COM server per component. If a component contains a COM server, this must be the key path for the component. Do not specify more than one file per component as a target for the Start menu or a Desktop shortcut. … And these rules do not even talk about component ids, update packages and upgrades which you need to understand as well. Lets suppose you install two MSIs (MSI1 and MSI2) which have the same ComponentId but different component names. Both do install the same file. What will happen when you uninstall MSI2?   Hm the file should stay there. But the component names are different. Yes and yes. But MSI uses not use the component name as key for the refcount. Instead the ComponentId column of the Component table which contains a GUID is used as identifier under which the refcount is stored. The components Comp1 and Comp2 are identical from the MSI perspective. After the installation of both MSIs the Component with the Id {100000….} has a refcount of two. After uninstallation of one MSI there is still a refcount of one which drops to zero just as expected when we uninstall the last msi. Then the file which was the same for both MSIs is deleted. You should remember that MSI keeps a refcount across MSIs for components with the same component id. MSI does manage components not the resources you did install. The resources associated with a component are then and only then deleted when the refcount of the component reaches zero.   The dependencies between features, components and resources can be described as relations. m,k are numbers >= 1, n can be 0. Inside a MSI the following relations are valid Feature    1  –> n Components Component    1 –> m Features Component      1  –>  k Resources These relations express that one feature can install several components and features can share components between them. Every (meaningful) component will install at least one resource which means that its name (primary key to stay in database speak) does occur in some other table in the Component column as value which installs some resource. Lets make it clear with an example. We want to install with the feature MainFeature some files a registry key and a shortcut. We can then create components Comp1..3 which are referenced by the resources defined in the corresponding tables.   Feature Component Registry File Shortcuts MainFeature Comp1 RegistryKey1     MainFeature Comp2   File.txt   MainFeature Comp3   File2.txt Shortcut to File2.txt   It is illegal that the same resource is part of more than one component since this would break the refcount mechanism. Lets illustrate this:            Feature ComponentId Resource Reference Count Feature1 {1000-…} File1.txt 1 Feature2 {2000-….} File1.txt 1 The installation part works well but what happens when you uninstall Feature2? Component {20000…} gets a refcount of zero where MSI deletes all resources belonging to this component. In this case File1.txt will be deleted. But Feature1 still has another component {10000…} with a refcount of one which means that the file was deleted too early. You just have ruined your installation. To fix it you then need to click on the Repair button under Add/Remove Programs to let MSI reinstall any missing registry keys, files or shortcuts. The vigilant reader might has noticed that there is more in the Component table. Beside its name and GUID it has also an installation directory, attributes and a KeyPath. The KeyPath is a reference to a file or registry key which is used to detect if the component is already installed. This becomes important when you repair or uninstall a component. To find out if the component is already installed MSI checks if the registry key or file referenced by the KeyPath property does exist. When it does not exist it assumes that it was either already uninstalled (can lead to problems during uninstall) or that it is already installed and all is fine. Why is this detail so important? Lets put all files into one component. The KeyPath should be then one of the files of your component to check if it was installed or not. When your installation becomes corrupt because a file was deleted you cannot repair it with the Repair button under Add/Remove Programs because MSI checks the component integrity via the Resource referenced by its KeyPath. As long as you did not delete the KeyPath file MSI thinks all resources with your component are installed and never executes any repair action. You get even more trouble when you try to remove files during an upgrade (you cannot remove files during an update) from your super component which contains all files. The only way out and therefore best practice is to assign for every resource you want to install an extra component. This ensures painless updatability and repairs and you have much less effort to remove specific files during an upgrade. In effect you get this best practice relation Feature 1  –> n Components Component   1  –>  1 Resources MSI Component Rules Rule 1 – One component per resource Every resource you want to install (file, registry key, value, environment value, shortcut, directory, …) must get its own component which does never change between versions as long as the install location is the same. Penalty If you add more than one resources to a component you will break the repair capability of MSI because the KeyPath is used to check if the component needs repair. MSI ComponentId Files MSI 1.0 {1000} File1-5 MSI 2.0 {2000} File2-5 You want to remove File1 in version 2.0 of your MSI. Since you want to keep the other files you create a new component and add them there. MSI will delete all files if the component refcount of {1000} drops to zero. The files you want to keep are added to the new component {2000}. Ok that does work if your upgrade does uninstall the old MSI first. This will cause the refcount of all previously installed components to reach zero which means that all files present in version 1.0 are deleted. But there is a faster way to perform your upgrade by first installing your new MSI and then remove the old one.  If you choose this upgrade path then you will loose File1-5 after your upgrade and not only File1 as intended by your new component design.   Rule 2 – Only add, never remove resources from a component If you did follow rule 1 you will not need Rule 2. You can add in a patch more resources to one component. That is ok. But you can never remove anything from it. There are tricky ways around that but I do not want to encourage bad component design. Penalty Lets assume you have 2 MSI files which install under the same component one file   MSI1 MSI2 {1000} - ComponentId {1000} – ComponentId File1.txt File2.txt   When you install and uninstall both MSIs you will end up with an installation where either File1 or File2 will be left. Why? It seems that MSI does not store the resources associated with each component in its internal database. Instead Windows will simply query the MSI that is currently uninstalled for all resources belonging to this component. Since it will find only one file and not two it will only uninstall one file. That is the main reason why you never can remove resources from a component!   Rule 3 Never Remove A Component From an Update MSI. This is the same as if you change the GUID of a component by accident for your new update package. The resulting update package will not contain all components from the previously installed package. Penalty When you remove a component from a feature MSI will set the feature state during update to Advertised and log a warning message into its log file when you did enable MSI logging. SELMGR: ComponentId '{2DCEA1BA-3E27-E222-484C-D0D66AEA4F62}' is registered to feature 'xxxxxxx, but is not present in the Component table.  Removal of components from a feature is not supported! MSI (c) (24:44) [07:53:13:436]: SELMGR: Removal of a component from a feature is not supported Advertised means that MSI treats all components of this feature as not installed. As a consequence during uninstall nothing will be removed since it is not installed! This is not only bad because uninstall does no longer work but this feature will also not get the required patches. All other features which have followed component versioning rules for update packages will be updated but the one faulty feature will not. This results in very hard to find bugs why an update was only partially successful. Things got better with Windows Installer 4.5 but you cannot rely on that nobody will use an older installer. It is a good idea to add to your update msiexec call MSIENFORCEUPGRADECOMPONENTRULES=1 which will abort the installation if you did violate this rule.

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  • How to find and fix performance problems in ORM powered applications

    - by FransBouma
    Once in a while we get requests about how to fix performance problems with our framework. As it comes down to following the same steps and looking into the same things every single time, I decided to write a blogpost about it instead, so more people can learn from this and solve performance problems in their O/R mapper powered applications. In some parts it's focused on LLBLGen Pro but it's also usable for other O/R mapping frameworks, as the vast majority of performance problems in O/R mapper powered applications are not specific for a certain O/R mapper framework. Too often, the developer looks at the wrong part of the application, trying to fix what isn't a problem in that part, and getting frustrated that 'things are so slow with <insert your favorite framework X here>'. I'm in the O/R mapper business for a long time now (almost 10 years, full time) and as it's a small world, we O/R mapper developers know almost all tricks to pull off by now: we all know what to do to make task ABC faster and what compromises (because there are almost always compromises) to deal with if we decide to make ABC faster that way. Some O/R mapper frameworks are faster in X, others in Y, but you can be sure the difference is mainly a result of a compromise some developers are willing to deal with and others aren't. That's why the O/R mapper frameworks on the market today are different in many ways, even though they all fetch and save entities from and to a database. I'm not suggesting there's no room for improvement in today's O/R mapper frameworks, there always is, but it's not a matter of 'the slowness of the application is caused by the O/R mapper' anymore. Perhaps query generation can be optimized a bit here, row materialization can be optimized a bit there, but it's mainly coming down to milliseconds. Still worth it if you're a framework developer, but it's not much compared to the time spend inside databases and in user code: if a complete fetch takes 40ms or 50ms (from call to entity object collection), it won't make a difference for your application as that 10ms difference won't be noticed. That's why it's very important to find the real locations of the problems so developers can fix them properly and don't get frustrated because their quest to get a fast, performing application failed. Performance tuning basics and rules Finding and fixing performance problems in any application is a strict procedure with four prescribed steps: isolate, analyze, interpret and fix, in that order. It's key that you don't skip a step nor make assumptions: these steps help you find the reason of a problem which seems to be there, and how to fix it or leave it as-is. Skipping a step, or when you assume things will be bad/slow without doing analysis will lead to the path of premature optimization and won't actually solve your problems, only create new ones. The most important rule of finding and fixing performance problems in software is that you have to understand what 'performance problem' actually means. Most developers will say "when a piece of software / code is slow, you have a performance problem". But is that actually the case? If I write a Linq query which will aggregate, group and sort 5 million rows from several tables to produce a resultset of 10 rows, it might take more than a couple of milliseconds before that resultset is ready to be consumed by other logic. If I solely look at the Linq query, the code consuming the resultset of the 10 rows and then look at the time it takes to complete the whole procedure, it will appear to me to be slow: all that time taken to produce and consume 10 rows? But if you look closer, if you analyze and interpret the situation, you'll see it does a tremendous amount of work, and in that light it might even be extremely fast. With every performance problem you encounter, always do realize that what you're trying to solve is perhaps not a technical problem at all, but a perception problem. The second most important rule you have to understand is based on the old saying "Penny wise, Pound Foolish": the part which takes e.g. 5% of the total time T for a given task isn't worth optimizing if you have another part which takes a much larger part of the total time T for that same given task. Optimizing parts which are relatively insignificant for the total time taken is not going to bring you better results overall, even if you totally optimize that part away. This is the core reason why analysis of the complete set of application parts which participate in a given task is key to being successful in solving performance problems: No analysis -> no problem -> no solution. One warning up front: hunting for performance will always include making compromises. Fast software can be made maintainable, but if you want to squeeze as much performance out of your software, you will inevitably be faced with the dilemma of compromising one or more from the group {readability, maintainability, features} for the extra performance you think you'll gain. It's then up to you to decide whether it's worth it. In almost all cases it's not. The reason for this is simple: the vast majority of performance problems can be solved by implementing the proper algorithms, the ones with proven Big O-characteristics so you know the performance you'll get plus you know the algorithm will work. The time taken by the algorithm implementing code is inevitable: you already implemented the best algorithm. You might find some optimizations on the technical level but in general these are minor. Let's look at the four steps to see how they guide us through the quest to find and fix performance problems. Isolate The first thing you need to do is to isolate the areas in your application which are assumed to be slow. For example, if your application is a web application and a given page is taking several seconds or even minutes to load, it's a good candidate to check out. It's important to start with the isolate step because it allows you to focus on a single code path per area with a clear begin and end and ignore the rest. The rest of the steps are taken per identified problematic area. Keep in mind that isolation focuses on tasks in an application, not code snippets. A task is something that's started in your application by either another task or the user, or another program, and has a beginning and an end. You can see a task as a piece of functionality offered by your application.  Analyze Once you've determined the problem areas, you have to perform analysis on the code paths of each area, to see where the performance problems occur and which areas are not the problem. This is a multi-layered effort: an application which uses an O/R mapper typically consists of multiple parts: there's likely some kind of interface (web, webservice, windows etc.), a part which controls the interface and business logic, the O/R mapper part and the RDBMS, all connected with either a network or inter-process connections provided by the OS or other means. Each of these parts, including the connectivity plumbing, eat up a part of the total time it takes to complete a task, e.g. load a webpage with all orders of a given customer X. To understand which parts participate in the task / area we're investigating and how much they contribute to the total time taken to complete the task, analysis of each participating task is essential. Start with the code you wrote which starts the task, analyze the code and track the path it follows through your application. What does the code do along the way, verify whether it's correct or not. Analyze whether you have implemented the right algorithms in your code for this particular area. Remember we're looking at one area at a time, which means we're ignoring all other code paths, just the code path of the current problematic area, from begin to end and back. Don't dig in and start optimizing at the code level just yet. We're just analyzing. If your analysis reveals big architectural stupidity, it's perhaps a good idea to rethink the architecture at this point. For the rest, we're analyzing which means we collect data about what could be wrong, for each participating part of the complete application. Reviewing the code you wrote is a good tool to get deeper understanding of what is going on for a given task but ultimately it lacks precision and overview what really happens: humans aren't good code interpreters, computers are. We therefore need to utilize tools to get deeper understanding about which parts contribute how much time to the total task, triggered by which other parts and for example how many times are they called. There are two different kind of tools which are necessary: .NET profilers and O/R mapper / RDBMS profilers. .NET profiling .NET profilers (e.g. dotTrace by JetBrains or Ants by Red Gate software) show exactly which pieces of code are called, how many times they're called, and the time it took to run that piece of code, at the method level and sometimes even at the line level. The .NET profilers are essential tools for understanding whether the time taken to complete a given task / area in your application is consumed by .NET code, where exactly in your code, the path to that code, how many times that code was called by other code and thus reveals where hotspots are located: the areas where a solution can be found. Importantly, they also reveal which areas can be left alone: remember our penny wise pound foolish saying: if a profiler reveals that a group of methods are fast, or don't contribute much to the total time taken for a given task, ignore them. Even if the code in them is perhaps complex and looks like a candidate for optimization: you can work all day on that, it won't matter.  As we're focusing on a single area of the application, it's best to start profiling right before you actually activate the task/area. Most .NET profilers support this by starting the application without starting the profiling procedure just yet. You navigate to the particular part which is slow, start profiling in the profiler, in your application you perform the actions which are considered slow, and afterwards you get a snapshot in the profiler. The snapshot contains the data collected by the profiler during the slow action, so most data is produced by code in the area to investigate. This is important, because it allows you to stay focused on a single area. O/R mapper and RDBMS profiling .NET profilers give you a good insight in the .NET side of things, but not in the RDBMS side of the application. As this article is about O/R mapper powered applications, we're also looking at databases, and the software making it possible to consume the database in your application: the O/R mapper. To understand which parts of the O/R mapper and database participate how much to the total time taken for task T, we need different tools. There are two kind of tools focusing on O/R mappers and database performance profiling: O/R mapper profilers and RDBMS profilers. For O/R mapper profilers, you can look at LLBLGen Prof by hibernating rhinos or the Linq to Sql/LLBLGen Pro profiler by Huagati. Hibernating rhinos also have profilers for other O/R mappers like NHibernate (NHProf) and Entity Framework (EFProf) and work the same as LLBLGen Prof. For RDBMS profilers, you have to look whether the RDBMS vendor has a profiler. For example for SQL Server, the profiler is shipped with SQL Server, for Oracle it's build into the RDBMS, however there are also 3rd party tools. Which tool you're using isn't really important, what's important is that you get insight in which queries are executed during the task / area we're currently focused on and how long they took. Here, the O/R mapper profilers have an advantage as they collect the time it took to execute the query from the application's perspective so they also collect the time it took to transport data across the network. This is important because a query which returns a massive resultset or a resultset with large blob/clob/ntext/image fields takes more time to get transported across the network than a small resultset and a database profiler doesn't take this into account most of the time. Another tool to use in this case, which is more low level and not all O/R mappers support it (though LLBLGen Pro and NHibernate as well do) is tracing: most O/R mappers offer some form of tracing or logging system which you can use to collect the SQL generated and executed and often also other activity behind the scenes. While tracing can produce a tremendous amount of data in some cases, it also gives insight in what's going on. Interpret After we've completed the analysis step it's time to look at the data we've collected. We've done code reviews to see whether we've done anything stupid and which parts actually take place and if the proper algorithms have been implemented. We've done .NET profiling to see which parts are choke points and how much time they contribute to the total time taken to complete the task we're investigating. We've performed O/R mapper profiling and RDBMS profiling to see which queries were executed during the task, how many queries were generated and executed and how long they took to complete, including network transportation. All this data reveals two things: which parts are big contributors to the total time taken and which parts are irrelevant. Both aspects are very important. The parts which are irrelevant (i.e. don't contribute significantly to the total time taken) can be ignored from now on, we won't look at them. The parts which contribute a lot to the total time taken are important to look at. We now have to first look at the .NET profiler results, to see whether the time taken is consumed in our own code, in .NET framework code, in the O/R mapper itself or somewhere else. For example if most of the time is consumed by DbCommand.ExecuteReader, the time it took to complete the task is depending on the time the data is fetched from the database. If there was just 1 query executed, according to tracing or O/R mapper profilers / RDBMS profilers, check whether that query is optimal, uses indexes or has to deal with a lot of data. Interpret means that you follow the path from begin to end through the data collected and determine where, along the path, the most time is contributed. It also means that you have to check whether this was expected or is totally unexpected. My previous example of the 10 row resultset of a query which groups millions of rows will likely reveal that a long time is spend inside the database and almost no time is spend in the .NET code, meaning the RDBMS part contributes the most to the total time taken, the rest is compared to that time, irrelevant. Considering the vastness of the source data set, it's expected this will take some time. However, does it need tweaking? Perhaps all possible tweaks are already in place. In the interpret step you then have to decide that further action in this area is necessary or not, based on what the analysis results show: if the analysis results were unexpected and in the area where the most time is contributed to the total time taken is room for improvement, action should be taken. If not, you can only accept the situation and move on. In all cases, document your decision together with the analysis you've done. If you decide that the perceived performance problem is actually expected due to the nature of the task performed, it's essential that in the future when someone else looks at the application and starts asking questions you can answer them properly and new analysis is only necessary if situations changed. Fix After interpreting the analysis results you've concluded that some areas need adjustment. This is the fix step: you're actively correcting the performance problem with proper action targeted at the real cause. In many cases related to O/R mapper powered applications it means you'll use different features of the O/R mapper to achieve the same goal, or apply optimizations at the RDBMS level. It could also mean you apply caching inside your application (compromise memory consumption over performance) to avoid unnecessary re-querying data and re-consuming the results. After applying a change, it's key you re-do the analysis and interpretation steps: compare the results and expectations with what you had before, to see whether your actions had any effect or whether it moved the problem to a different part of the application. Don't fall into the trap to do partly analysis: do the full analysis again: .NET profiling and O/R mapper / RDBMS profiling. It might very well be that the changes you've made make one part faster but another part significantly slower, in such a way that the overall problem hasn't changed at all. Performance tuning is dealing with compromises and making choices: to use one feature over the other, to accept a higher memory footprint, to go away from the strict-OO path and execute queries directly onto the RDBMS, these are choices and compromises which will cross your path if you want to fix performance problems with respect to O/R mappers or data-access and databases in general. In most cases it's not a big issue: alternatives are often good choices too and the compromises aren't that hard to deal with. What is important is that you document why you made a choice, a compromise: which analysis data, which interpretation led you to the choice made. This is key for good maintainability in the years to come. Most common performance problems with O/R mappers Below is an incomplete list of common performance problems related to data-access / O/R mappers / RDBMS code. It will help you with fixing the hotspots you found in the interpretation step. SELECT N+1: (Lazy-loading specific). Lazy loading triggered performance bottlenecks. Consider a list of Orders bound to a grid. You have a Field mapped onto a related field in Order, Customer.CompanyName. Showing this column in the grid will make the grid fetch (indirectly) for each row the Customer row. This means you'll get for the single list not 1 query (for the orders) but 1+(the number of orders shown) queries. To solve this: use eager loading using a prefetch path to fetch the customers with the orders. SELECT N+1 is easy to spot with an O/R mapper profiler or RDBMS profiler: if you see a lot of identical queries executed at once, you have this problem. Prefetch paths using many path nodes or sorting, or limiting. Eager loading problem. Prefetch paths can help with performance, but as 1 query is fetched per node, it can be the number of data fetched in a child node is bigger than you think. Also consider that data in every node is merged on the client within the parent. This is fast, but it also can take some time if you fetch massive amounts of entities. If you keep fetches small, you can use tuning parameters like the ParameterizedPrefetchPathThreshold setting to get more optimal queries. Deep inheritance hierarchies of type Target Per Entity/Type. If you use inheritance of type Target per Entity / Type (each type in the inheritance hierarchy is mapped onto its own table/view), fetches will join subtype- and supertype tables in many cases, which can lead to a lot of performance problems if the hierarchy has many types. With this problem, keep inheritance to a minimum if possible, or switch to a hierarchy of type Target Per Hierarchy, which means all entities in the inheritance hierarchy are mapped onto the same table/view. Of course this has its own set of drawbacks, but it's a compromise you might want to take. Fetching massive amounts of data by fetching large lists of entities. LLBLGen Pro supports paging (and limiting the # of rows returned), which is often key to process through large sets of data. Use paging on the RDBMS if possible (so a query is executed which returns only the rows in the page requested). When using paging in a web application, be sure that you switch server-side paging on on the datasourcecontrol used. In this case, paging on the grid alone is not enough: this can lead to fetching a lot of data which is then loaded into the grid and paged there. Keep note that analyzing queries for paging could lead to the false assumption that paging doesn't occur, e.g. when the query contains a field of type ntext/image/clob/blob and DISTINCT can't be applied while it should have (e.g. due to a join): the datareader will do DISTINCT filtering on the client. this is a little slower but it does perform paging functionality on the data-reader so it won't fetch all rows even if the query suggests it does. Fetch massive amounts of data because blob/clob/ntext/image fields aren't excluded. LLBLGen Pro supports field exclusion for queries. You can exclude fields (also in prefetch paths) per query to avoid fetching all fields of an entity, e.g. when you don't need them for the logic consuming the resultset. Excluding fields can greatly reduce the amount of time spend on data-transport across the network. Use this optimization if you see that there's a big difference between query execution time on the RDBMS and the time reported by the .NET profiler for the ExecuteReader method call. Doing client-side aggregates/scalar calculations by consuming a lot of data. If possible, try to formulate a scalar query or group by query using the projection system or GetScalar functionality of LLBLGen Pro to do data consumption on the RDBMS server. It's far more efficient to process data on the RDBMS server than to first load it all in memory, then traverse the data in-memory to calculate a value. Using .ToList() constructs inside linq queries. It might be you use .ToList() somewhere in a Linq query which makes the query be run partially in-memory. Example: var q = from c in metaData.Customers.ToList() where c.Country=="Norway" select c; This will actually fetch all customers in-memory and do an in-memory filtering, as the linq query is defined on an IEnumerable<T>, and not on the IQueryable<T>. Linq is nice, but it can often be a bit unclear where some parts of a Linq query might run. Fetching all entities to delete into memory first. To delete a set of entities it's rather inefficient to first fetch them all into memory and then delete them one by one. It's more efficient to execute a DELETE FROM ... WHERE query on the database directly to delete the entities in one go. LLBLGen Pro supports this feature, and so do some other O/R mappers. It's not always possible to do this operation in the context of an O/R mapper however: if an O/R mapper relies on a cache, these kind of operations are likely not supported because they make it impossible to track whether an entity is actually removed from the DB and thus can be removed from the cache. Fetching all entities to update with an expression into memory first. Similar to the previous point: it is more efficient to update a set of entities directly with a single UPDATE query using an expression instead of fetching the entities into memory first and then updating the entities in a loop, and afterwards saving them. It might however be a compromise you don't want to take as it is working around the idea of having an object graph in memory which is manipulated and instead makes the code fully aware there's a RDBMS somewhere. Conclusion Performance tuning is almost always about compromises and making choices. It's also about knowing where to look and how the systems in play behave and should behave. The four steps I provided should help you stay focused on the real problem and lead you towards the solution. Knowing how to optimally use the systems participating in your own code (.NET framework, O/R mapper, RDBMS, network/services) is key for success as well as knowing what's going on inside the application you built. I hope you'll find this guide useful in tracking down performance problems and dealing with them in a useful way.  

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  • Using Rich Text Editor (WYSIWYG) in ASP.NET MVC

    - by imran_ku07
       Introduction:          In ASP.NET MVC forum I found some question regarding a sample HTML Rich Text Box Editor(also known as wysiwyg).So i decided to create a sample ASP.NET MVC web application which will use a Rich Text Box Editor. There are are lot of Html Editors are available, but for creating a sample application, i decided to use cross-browser WYSIWYG editor from openwebware. In this article I will discuss what changes needed to work this editor with ASP.NET MVC. Also I had attached the sample application for download at http://www.speedfile.org/155076. Also note that I will only show the important features, not discuss every feature in detail.   Description:          So Let's start create a sample ASP.NET MVC application. You need to add the following script files,         jquery-1.3.2.min.js        jquery_form.js        wysiwyg.js        wysiwyg-settings.js        wysiwyg-popup.js          Just put these files inside Scripts folder. Also put wysiwyg.css in your Content Folder and add the following folders in your project        addons        popups          Also create a empty folder Uploads to store the uploaded images. Next open wysiwyg.js and set your configuration                  // Images Directory        this.ImagesDir = "/addons/imagelibrary/images/";                // Popups Directory        this.PopupsDir = "/popups/";                // CSS Directory File        this.CSSFile = "/Content/wysiwyg.css";              Next create a simple View TextEditor.aspx inside View / Home Folder and add the folllowing HTML.        <%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage" %>            <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">        <html >            <head runat="server">                <title>TextEditor</title>                <script src="../../Scripts/wysiwyg.js" type="text/javascript"></script>                <script src="../../Scripts/wysiwyg-settings.js" type="text/javascript"></script>                <script type="text/javascript">                            WYSIWYG.attach('text', full);                            </script>            </head>            <body>                <% using (Html.BeginForm()){ %>                    <textarea id="text" name="test2" style="width:850px;height:200px;">                    </textarea>                    <input type="submit" value="submit" />                <%} %>            </body>        </html>                  Here i have just added a text area control and a submit button inside a form. Note the id of text area and WYSIWYG.attach function's first parameter is same and next to watch is the HomeController.cs        using System;        using System.Collections.Generic;        using System.Linq;        using System.Web;        using System.Web.Mvc;        using System.IO;        namespace HtmlTextEditor.Controllers        {            [HandleError]            public class HomeController : Controller            {                public ActionResult Index()                {                    ViewData["Message"] = "Welcome to ASP.NET MVC!";                    return View();                }                    public ActionResult About()                {                                return View();                }                        public ActionResult TextEditor()                {                    return View();                }                [AcceptVerbs(HttpVerbs.Post)]                [ValidateInput(false)]                public ActionResult TextEditor(string test2)                {                    Session["html"] = test2;                            return RedirectToAction("Index");                }                        public ActionResult UploadImage()                {                    if (Request.Files[0].FileName != "")                    {                        Request.Files[0].SaveAs(Server.MapPath("~/Uploads/" + Path.GetFileName(Request.Files[0].FileName)));                        return Content(Url.Content("~/Uploads/" + Path.GetFileName(Request.Files[0].FileName)));                    }                    return Content("a");                }            }        }          So simple code, just save the posted Html into Session. Here the parameter of TextArea action is test2 which is same as textarea control name of TextArea.aspx View. Also note ValidateInputAttribute is false, so it's up to you to defends against XSS. Also there is an Action method which simply saves the file inside Upload Folder.          I am uploading the file using Jquery Form Plugin. Here is the code which is found in insert_image.html inside addons folder,        function ChangeImage() {            var myform=document.getElementById("formUpload");                    $(myform).ajaxSubmit({success: function(responseText){                insertImage(responseText);                        window.close();                }            });        }          and here is the Index View which simply renders the html of Editor which was saved in Session        <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" %>        <asp:Content ID="indexTitle" ContentPlaceHolderID="TitleContent" runat="server">            Home Page        </asp:Content>        <asp:Content ID="indexContent" ContentPlaceHolderID="MainContent" runat="server">            <h2><%= Html.Encode(ViewData["Message"]) %></h2>            <p>                To learn more about ASP.NET MVC visit <a href="http://asp.net/mvc" title="ASP.NET MVC Website">http://asp.net/mvc</a>.            </p>            <%if (Session["html"] != null){                  Response.Write(Session["html"].ToString());            } %>                    </asp:Content>   Summary:          Hopefully you will enjoy this article. Just download the code and see the effect. From security point, you must handle the XSS attack your self. I had uploaded the sample application in http://www.speedfile.org/155076

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  • Syncing Data with a Server using Silverlight and HTTP Polling Duplex

    - by dwahlin
    Many applications have the need to stay in-sync with data provided by a service. Although web applications typically rely on standard polling techniques to check if data has changed, Silverlight provides several interesting options for keeping an application in-sync that rely on server “push” technologies. A few years back I wrote several blog posts covering different “push” technologies available in Silverlight that rely on sockets or HTTP Polling Duplex. We recently had a project that looked like it could benefit from pushing data from a server to one or more clients so I thought I’d revisit the subject and provide some updates to the original code posted. If you’ve worked with AJAX before in Web applications then you know that until browsers fully support web sockets or other duplex (bi-directional communication) technologies that it’s difficult to keep applications in-sync with a server without relying on polling. The problem with polling is that you have to check for changes on the server on a timed-basis which can often be wasteful and take up unnecessary resources. With server “push” technologies, data can be pushed from the server to the client as it changes. Once the data is received, the client can update the user interface as appropriate. Using “push” technologies allows the client to listen for changes from the data but stay 100% focused on client activities as opposed to worrying about polling and asking the server if anything has changed. Silverlight provides several options for pushing data from a server to a client including sockets, TCP bindings and HTTP Polling Duplex.  Each has its own strengths and weaknesses as far as performance and setup work with HTTP Polling Duplex arguably being the easiest to setup and get going.  In this article I’ll demonstrate how HTTP Polling Duplex can be used in Silverlight 4 applications to push data and show how you can create a WCF server that provides an HTTP Polling Duplex binding that a Silverlight client can consume.   What is HTTP Polling Duplex? Technologies that allow data to be pushed from a server to a client rely on duplex functionality. Duplex (or bi-directional) communication allows data to be passed in both directions.  A client can call a service and the server can call the client. HTTP Polling Duplex (as its name implies) allows a server to communicate with a client without forcing the client to constantly poll the server. It has the benefit of being able to run on port 80 making setup a breeze compared to the other options which require specific ports to be used and cross-domain policy files to be exposed on port 943 (as with sockets and TCP bindings). Having said that, if you’re looking for the best speed possible then sockets and TCP bindings are the way to go. But, they’re not the only game in town when it comes to duplex communication. The first time I heard about HTTP Polling Duplex (initially available in Silverlight 2) I wasn’t exactly sure how it was any better than standard polling used in AJAX applications. I read the Silverlight SDK, looked at various resources and generally found the following definition unhelpful as far as understanding the actual benefits that HTTP Polling Duplex provided: "The Silverlight client periodically polls the service on the network layer, and checks for any new messages that the service wants to send on the callback channel. The service queues all messages sent on the client callback channel and delivers them to the client when the client polls the service." Although the previous definition explained the overall process, it sounded as if standard polling was used. Fortunately, Microsoft’s Scott Guthrie provided me with a more clear definition several years back that explains the benefits provided by HTTP Polling Duplex quite well (used with his permission): "The [HTTP Polling Duplex] duplex support does use polling in the background to implement notifications – although the way it does it is different than manual polling. It initiates a network request, and then the request is effectively “put to sleep” waiting for the server to respond (it doesn’t come back immediately). The server then keeps the connection open but not active until it has something to send back (or the connection times out after 90 seconds – at which point the duplex client will connect again and wait). This way you are avoiding hitting the server repeatedly – but still get an immediate response when there is data to send." After hearing Scott’s definition the light bulb went on and it all made sense. A client makes a request to a server to check for changes, but instead of the request returning immediately, it parks itself on the server and waits for data. It’s kind of like waiting to pick up a pizza at the store. Instead of calling the store over and over to check the status, you sit in the store and wait until the pizza (the request data) is ready. Once it’s ready you take it back home (to the client). This technique provides a lot of efficiency gains over standard polling techniques even though it does use some polling of its own as a request is initially made from a client to a server. So how do you implement HTTP Polling Duplex in your Silverlight applications? Let’s take a look at the process by starting with the server. Creating an HTTP Polling Duplex WCF Service Creating a WCF service that exposes an HTTP Polling Duplex binding is straightforward as far as coding goes. Add some one way operations into an interface, create a client callback interface and you’re ready to go. The most challenging part comes into play when configuring the service to properly support the necessary binding and that’s more of a cut and paste operation once you know the configuration code to use. To create an HTTP Polling Duplex service you’ll need to expose server-side and client-side interfaces and reference the System.ServiceModel.PollingDuplex assembly (located at C:\Program Files (x86)\Microsoft SDKs\Silverlight\v4.0\Libraries\Server on my machine) in the server project. For the demo application I upgraded a basketball simulation service to support the latest polling duplex assemblies. The service simulates a simple basketball game using a Game class and pushes information about the game such as score, fouls, shots and more to the client as the game changes over time. Before jumping too far into the game push service, it’s important to discuss two interfaces used by the service to communicate in a bi-directional manner. The first is called IGameStreamService and defines the methods/operations that the client can call on the server (see Listing 1). The second is IGameStreamClient which defines the callback methods that a server can use to communicate with a client (see Listing 2).   [ServiceContract(Namespace = "Silverlight", CallbackContract = typeof(IGameStreamClient))] public interface IGameStreamService { [OperationContract(IsOneWay = true)] void GetTeamData(); } Listing 1. The IGameStreamService interface defines server operations that can be called on the server.   [ServiceContract] public interface IGameStreamClient { [OperationContract(IsOneWay = true)] void ReceiveTeamData(List<Team> teamData); [OperationContract(IsOneWay = true, AsyncPattern=true)] IAsyncResult BeginReceiveGameData(GameData gameData, AsyncCallback callback, object state); void EndReceiveGameData(IAsyncResult result); } Listing 2. The IGameStreamClient interfaces defines client operations that a server can call.   The IGameStreamService interface is decorated with the standard ServiceContract attribute but also contains a value for the CallbackContract property.  This property is used to define the interface that the client will expose (IGameStreamClient in this example) and use to receive data pushed from the service. Notice that each OperationContract attribute in both interfaces sets the IsOneWay property to true. This means that the operation can be called and passed data as appropriate, however, no data will be passed back. Instead, data will be pushed back to the client as it’s available.  Looking through the IGameStreamService interface you can see that the client can request team data whereas the IGameStreamClient interface allows team and game data to be received by the client. One interesting point about the IGameStreamClient interface is the inclusion of the AsyncPattern property on the BeginReceiveGameData operation. I initially created this operation as a standard one way operation and it worked most of the time. However, as I disconnected clients and reconnected new ones game data wasn’t being passed properly. After researching the problem more I realized that because the service could take up to 7 seconds to return game data, things were getting hung up. By setting the AsyncPattern property to true on the BeginReceivedGameData operation and providing a corresponding EndReceiveGameData operation I was able to get around this problem and get everything running properly. I’ll provide more details on the implementation of these two methods later in this post. Once the interfaces were created I moved on to the game service class. The first order of business was to create a class that implemented the IGameStreamService interface. Since the service can be used by multiple clients wanting game data I added the ServiceBehavior attribute to the class definition so that I could set its InstanceContextMode to InstanceContextMode.Single (in effect creating a Singleton service object). Listing 3 shows the game service class as well as its fields and constructor.   [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, InstanceContextMode = InstanceContextMode.Single)] public class GameStreamService : IGameStreamService { object _Key = new object(); Game _Game = null; Timer _Timer = null; Random _Random = null; Dictionary<string, IGameStreamClient> _ClientCallbacks = new Dictionary<string, IGameStreamClient>(); static AsyncCallback _ReceiveGameDataCompleted = new AsyncCallback(ReceiveGameDataCompleted); public GameStreamService() { _Game = new Game(); _Timer = new Timer { Enabled = false, Interval = 2000, AutoReset = true }; _Timer.Elapsed += new ElapsedEventHandler(_Timer_Elapsed); _Timer.Start(); _Random = new Random(); }} Listing 3. The GameStreamService implements the IGameStreamService interface which defines a callback contract that allows the service class to push data back to the client. By implementing the IGameStreamService interface, GameStreamService must supply a GetTeamData() method which is responsible for supplying information about the teams that are playing as well as individual players.  GetTeamData() also acts as a client subscription method that tracks clients wanting to receive game data.  Listing 4 shows the GetTeamData() method. public void GetTeamData() { //Get client callback channel var context = OperationContext.Current; var sessionID = context.SessionId; var currClient = context.GetCallbackChannel<IGameStreamClient>(); context.Channel.Faulted += Disconnect; context.Channel.Closed += Disconnect; IGameStreamClient client; if (!_ClientCallbacks.TryGetValue(sessionID, out client)) { lock (_Key) { _ClientCallbacks[sessionID] = currClient; } } currClient.ReceiveTeamData(_Game.GetTeamData()); //Start timer which when fired sends updated score information to client if (!_Timer.Enabled) { _Timer.Enabled = true; } } Listing 4. The GetTeamData() method subscribes a given client to the game service and returns. The key the line of code in the GetTeamData() method is the call to GetCallbackChannel<IGameStreamClient>().  This method is responsible for accessing the calling client’s callback channel. The callback channel is defined by the IGameStreamClient interface shown earlier in Listing 2 and used by the server to communicate with the client. Before passing team data back to the client, GetTeamData() grabs the client’s session ID and checks if it already exists in the _ClientCallbacks dictionary object used to track clients wanting callbacks from the server. If the client doesn’t exist it adds it into the collection. It then pushes team data from the Game class back to the client by calling ReceiveTeamData().  Since the service simulates a basketball game, a timer is then started if it’s not already enabled which is then used to randomly send data to the client. When the timer fires, game data is pushed down to the client. Listing 5 shows the _Timer_Elapsed() method that is called when the timer fires as well as the SendGameData() method used to send data to the client. void _Timer_Elapsed(object sender, ElapsedEventArgs e) { int interval = _Random.Next(3000, 7000); lock (_Key) { _Timer.Interval = interval; _Timer.Enabled = false; } SendGameData(_Game.GetGameData()); } private void SendGameData(GameData gameData) { var cbs = _ClientCallbacks.Where(cb => ((IContextChannel)cb.Value).State == CommunicationState.Opened); for (int i = 0; i < cbs.Count(); i++) { var cb = cbs.ElementAt(i).Value; try { cb.BeginReceiveGameData(gameData, _ReceiveGameDataCompleted, cb); } catch (TimeoutException texp) { //Log timeout error } catch (CommunicationException cexp) { //Log communication error } } lock (_Key) _Timer.Enabled = true; } private static void ReceiveGameDataCompleted(IAsyncResult result) { try { ((IGameStreamClient)(result.AsyncState)).EndReceiveGameData(result); } catch (CommunicationException) { // empty } catch (TimeoutException) { // empty } } LIsting 5. _Timer_Elapsed is used to simulate time in a basketball game. When _Timer_Elapsed() fires the SendGameData() method is called which iterates through the clients wanting to be notified of changes. As each client is identified, their respective BeginReceiveGameData() method is called which ultimately pushes game data down to the client. Recall that this method was defined in the client callback interface named IGameStreamClient shown earlier in Listing 2. Notice that BeginReceiveGameData() accepts _ReceiveGameDataCompleted as its second parameter (an AsyncCallback delegate defined in the service class) and passes the client callback as the third parameter. The initial version of the sample application had a standard ReceiveGameData() method in the client callback interface. However, sometimes the client callbacks would work properly and sometimes they wouldn’t which was a little baffling at first glance. After some investigation I realized that I needed to implement an asynchronous pattern for client callbacks to work properly since 3 – 7 second delays are occurring as a result of the timer. Once I added the BeginReceiveGameData() and ReceiveGameDataCompleted() methods everything worked properly since each call was handled in an asynchronous manner. The final task that had to be completed to get the server working properly with HTTP Polling Duplex was adding configuration code into web.config. In the interest of brevity I won’t post all of the code here since the sample application includes everything you need. However, Listing 6 shows the key configuration code to handle creating a custom binding named pollingDuplexBinding and associate it with the service’s endpoint.   <bindings> <customBinding> <binding name="pollingDuplexBinding"> <binaryMessageEncoding /> <pollingDuplex maxPendingSessions="2147483647" maxPendingMessagesPerSession="2147483647" inactivityTimeout="02:00:00" serverPollTimeout="00:05:00"/> <httpTransport /> </binding> </customBinding> </bindings> <services> <service name="GameService.GameStreamService" behaviorConfiguration="GameStreamServiceBehavior"> <endpoint address="" binding="customBinding" bindingConfiguration="pollingDuplexBinding" contract="GameService.IGameStreamService"/> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" /> </service> </services>   Listing 6. Configuring an HTTP Polling Duplex binding in web.config and associating an endpoint with it. Calling the Service and Receiving “Pushed” Data Calling the service and handling data that is pushed from the server is a simple and straightforward process in Silverlight. Since the service is configured with a MEX endpoint and exposes a WSDL file, you can right-click on the Silverlight project and select the standard Add Service Reference item. After the web service proxy is created you may notice that the ServiceReferences.ClientConfig file only contains an empty configuration element instead of the normal configuration elements created when creating a standard WCF proxy. You can certainly update the file if you want to read from it at runtime but for the sample application I fed the service URI directly to the service proxy as shown next: var address = new EndpointAddress("http://localhost.:5661/GameStreamService.svc"); var binding = new PollingDuplexHttpBinding(); _Proxy = new GameStreamServiceClient(binding, address); _Proxy.ReceiveTeamDataReceived += _Proxy_ReceiveTeamDataReceived; _Proxy.ReceiveGameDataReceived += _Proxy_ReceiveGameDataReceived; _Proxy.GetTeamDataAsync(); This code creates the proxy and passes the endpoint address and binding to use to its constructor. It then wires the different receive events to callback methods and calls GetTeamDataAsync().  Calling GetTeamDataAsync() causes the server to store the client in the server-side dictionary collection mentioned earlier so that it can receive data that is pushed.  As the server-side timer fires and game data is pushed to the client, the user interface is updated as shown in Listing 7. Listing 8 shows the _Proxy_ReceiveGameDataReceived() method responsible for handling the data and calling UpdateGameData() to process it.   Listing 7. The Silverlight interface. Game data is pushed from the server to the client using HTTP Polling Duplex. void _Proxy_ReceiveGameDataReceived(object sender, ReceiveGameDataReceivedEventArgs e) { UpdateGameData(e.gameData); } private void UpdateGameData(GameData gameData) { //Update Score this.tbTeam1Score.Text = gameData.Team1Score.ToString(); this.tbTeam2Score.Text = gameData.Team2Score.ToString(); //Update ball visibility if (gameData.Action != ActionsEnum.Foul) { if (tbTeam1.Text == gameData.TeamOnOffense) { AnimateBall(this.BB1, this.BB2); } else //Team 2 { AnimateBall(this.BB2, this.BB1); } } if (this.lbActions.Items.Count > 9) this.lbActions.Items.Clear(); this.lbActions.Items.Add(gameData.LastAction); if (this.lbActions.Visibility == Visibility.Collapsed) this.lbActions.Visibility = Visibility.Visible; } private void AnimateBall(Image onBall, Image offBall) { this.FadeIn.Stop(); Storyboard.SetTarget(this.FadeInAnimation, onBall); Storyboard.SetTarget(this.FadeOutAnimation, offBall); this.FadeIn.Begin(); } Listing 8. As the server pushes game data, the client’s _Proxy_ReceiveGameDataReceived() method is called to process the data. In a real-life application I’d go with a ViewModel class to handle retrieving team data, setup data bindings and handle data that is pushed from the server. However, for the sample application I wanted to focus on HTTP Polling Duplex and keep things as simple as possible.   Summary Silverlight supports three options when duplex communication is required in an application including TCP bindins, sockets and HTTP Polling Duplex. In this post you’ve seen how HTTP Polling Duplex interfaces can be created and implemented on the server as well as how they can be consumed by a Silverlight client. HTTP Polling Duplex provides a nice way to “push” data from a server while still allowing the data to flow over port 80 or another port of your choice.   Sample Application Download

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  • The Incremental Architect&acute;s Napkin &ndash; #3 &ndash; Make Evolvability inevitable

    - by Ralf Westphal
    Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/06/04/the-incremental-architectacutes-napkin-ndash-3-ndash-make-evolvability-inevitable.aspxThe easier something to measure the more likely it will be produced. Deviations between what is and what should be can be readily detected. That´s what automated acceptance tests are for. That´s what sprint reviews in Scrum are for. It´s no small wonder our software looks like it looks. It has all the traits whose conformance with requirements can easily be measured. And it´s lacking traits which cannot easily be measured. Evolvability (or Changeability) is such a trait. If an operation is correct, if an operation if fast enough, that can be checked very easily. But whether Evolvability is high or low, that cannot be checked by taking a measure or two. Evolvability might correlate with certain traits, e.g. number of lines of code (LOC) per function or Cyclomatic Complexity or test coverage. But there is no threshold value signalling “evolvability too low”; also Evolvability is hardly tangible for the customer. Nevertheless Evolvability is of great importance - at least in the long run. You can get away without much of it for a short time. Eventually, though, it´s needed like any other requirement. Or even more. Because without Evolvability no other requirement can be implemented. Evolvability is the foundation on which all else is build. Such fundamental importance is in stark contrast with its immeasurability. To compensate this, Evolvability must be put at the very center of software development. It must become the hub around everything else revolves. Since we cannot measure Evolvability, though, we cannot start watching it more. Instead we need to establish practices to keep it high (enough) at all times. Chefs have known that for long. That´s why everybody in a restaurant kitchen is constantly seeing after cleanliness. Hygiene is important as is to have clean tools at standardized locations. Only then the health of the patrons can be guaranteed and production efficiency is constantly high. Still a kitchen´s level of cleanliness is easier to measure than software Evolvability. That´s why important practices like reviews, pair programming, or TDD are not enough, I guess. What we need to keep Evolvability in focus and high is… to continually evolve. Change must not be something to avoid but too embrace. To me that means the whole change cycle from requirement analysis to delivery needs to be gone through more often. Scrum´s sprints of 4, 2 even 1 week are too long. Kanban´s flow of user stories across is too unreliable; it takes as long as it takes. Instead we should fix the cycle time at 2 days max. I call that Spinning. No increment must take longer than from this morning until tomorrow evening to finish. Then it should be acceptance checked by the customer (or his/her representative, e.g. a Product Owner). For me there are several resasons for such a fixed and short cycle time for each increment: Clear expectations Absolute estimates (“This will take X days to complete.”) are near impossible in software development as explained previously. Too much unplanned research and engineering work lurk in every feature. And then pervasive interruptions of work by peers and management. However, the smaller the scope the better our absolute estimates become. That´s because we understand better what really are the requirements and what the solution should look like. But maybe more importantly the shorter the timespan the more we can control how we use our time. So much can happen over the course of a week and longer timespans. But if push comes to shove I can block out all distractions and interruptions for a day or possibly two. That´s why I believe we can give rough absolute estimates on 3 levels: Noon Tonight Tomorrow Think of a meeting with a Product Owner at 8:30 in the morning. If she asks you, how long it will take you to implement a user story or bug fix, you can say, “It´ll be fixed by noon.”, or you can say, “I can manage to implement it until tonight before I leave.”, or you can say, “You´ll get it by tomorrow night at latest.” Yes, I believe all else would be naive. If you´re not confident to get something done by tomorrow night (some 34h from now) you just cannot reliably commit to any timeframe. That means you should not promise anything, you should not even start working on the issue. So when estimating use these four categories: Noon, Tonight, Tomorrow, NoClue - with NoClue meaning the requirement needs to be broken down further so each aspect can be assigned to one of the first three categories. If you like absolute estimates, here you go. But don´t do deep estimates. Don´t estimate dozens of issues; don´t think ahead (“Issue A is a Tonight, then B will be a Tomorrow, after that it´s C as a Noon, finally D is a Tonight - that´s what I´ll do this week.”). Just estimate so Work-in-Progress (WIP) is 1 for everybody - plus a small number of buffer issues. To be blunt: Yes, this makes promises impossible as to what a team will deliver in terms of scope at a certain date in the future. But it will give a Product Owner a clear picture of what to pull for acceptance feedback tonight and tomorrow. Trust through reliability Our trade is lacking trust. Customers don´t trust software companies/departments much. Managers don´t trust developers much. I find that perfectly understandable in the light of what we´re trying to accomplish: delivering software in the face of uncertainty by means of material good production. Customers as well as managers still expect software development to be close to production of houses or cars. But that´s a fundamental misunderstanding. Software development ist development. It´s basically research. As software developers we´re constantly executing experiments to find out what really provides value to users. We don´t know what they need, we just have mediated hypothesises. That´s why we cannot reliably deliver on preposterous demands. So trust is out of the window in no time. If we switch to delivering in short cycles, though, we can regain trust. Because estimates - explicit or implicit - up to 32 hours at most can be satisfied. I´d say: reliability over scope. It´s more important to reliably deliver what was promised then to cover a lot of requirement area. So when in doubt promise less - but deliver without delay. Deliver on scope (Functionality and Quality); but also deliver on Evolvability, i.e. on inner quality according to accepted principles. Always. Trust will be the reward. Less complexity of communication will follow. More goodwill buffer will follow. So don´t wait for some Kanban board to show you, that flow can be improved by scheduling smaller stories. You don´t need to learn that the hard way. Just start with small batch sizes of three different sizes. Fast feedback What has been finished can be checked for acceptance. Why wait for a sprint of several weeks to end? Why let the mental model of the issue and its solution dissipate? If you get final feedback after one or two weeks, you hardly remember what you did and why you did it. Resoning becomes hard. But more importantly youo probably are not in the mood anymore to go back to something you deemed done a long time ago. It´s boring, it´s frustrating to open up that mental box again. Learning is harder the longer it takes from event to feedback. Effort can be wasted between event (finishing an issue) and feedback, because other work might go in the wrong direction based on false premises. Checking finished issues for acceptance is the most important task of a Product Owner. It´s even more important than planning new issues. Because as long as work started is not released (accepted) it´s potential waste. So before starting new work better make sure work already done has value. By putting the emphasis on acceptance rather than planning true pull is established. As long as planning and starting work is more important, it´s a push process. Accept a Noon issue on the same day before leaving. Accept a Tonight issue before leaving today or first thing tomorrow morning. Accept a Tomorrow issue tomorrow night before leaving or early the day after tomorrow. After acceptance the developer(s) can start working on the next issue. Flexibility As if reliability/trust and fast feedback for less waste weren´t enough economic incentive, there is flexibility. After each issue the Product Owner can change course. If on Monday morning feature slices A, B, C, D, E were important and A, B, C were scheduled for acceptance by Monday evening and Tuesday evening, the Product Owner can change her mind at any time. Maybe after A got accepted she asks for continuation with D. But maybe, just maybe, she has gotten a completely different idea by then. Maybe she wants work to continue on F. And after B it´s neither D nor E, but G. And after G it´s D. With Spinning every 32 hours at latest priorities can be changed. And nothing is lost. Because what got accepted is of value. It provides an incremental value to the customer/user. Or it provides internal value to the Product Owner as increased knowledge/decreased uncertainty. I find such reactivity over commitment economically very benefical. Why commit a team to some workload for several weeks? It´s unnecessary at beast, and inflexible and wasteful at worst. If we cannot promise delivery of a certain scope on a certain date - which is what customers/management usually want -, we can at least provide them with unpredecented flexibility in the face of high uncertainty. Where the path is not clear, cannot be clear, make small steps so you´re able to change your course at any time. Premature completion Customers/management are used to premeditating budgets. They want to know exactly how much to pay for a certain amount of requirements. That´s understandable. But it does not match with the nature of software development. We should know that by now. Maybe there´s somewhere in the world some team who can consistently deliver on scope, quality, and time, and budget. Great! Congratulations! I, however, haven´t seen such a team yet. Which does not mean it´s impossible, but I think it´s nothing I can recommend to strive for. Rather I´d say: Don´t try this at home. It might hurt you one way or the other. However, what we can do, is allow customers/management stop work on features at any moment. With spinning every 32 hours a feature can be declared as finished - even though it might not be completed according to initial definition. I think, progress over completion is an important offer software development can make. Why think in terms of completion beyond a promise for the next 32 hours? Isn´t it more important to constantly move forward? Step by step. We´re not running sprints, we´re not running marathons, not even ultra-marathons. We´re in the sport of running forever. That makes it futile to stare at the finishing line. The very concept of a burn-down chart is misleading (in most cases). Whoever can only think in terms of completed requirements shuts out the chance for saving money. The requirements for a features mostly are uncertain. So how does a Product Owner know in the first place, how much is needed. Maybe more than specified is needed - which gets uncovered step by step with each finished increment. Maybe less than specified is needed. After each 4–32 hour increment the Product Owner can do an experient (or invite users to an experiment) if a particular trait of the software system is already good enough. And if so, she can switch the attention to a different aspect. In the end, requirements A, B, C then could be finished just 70%, 80%, and 50%. What the heck? It´s good enough - for now. 33% money saved. Wouldn´t that be splendid? Isn´t that a stunning argument for any budget-sensitive customer? You can save money and still get what you need? Pull on practices So far, in addition to more trust, more flexibility, less money spent, Spinning led to “doing less” which also means less code which of course means higher Evolvability per se. Last but not least, though, I think Spinning´s short acceptance cycles have one more effect. They excert pull-power on all sorts of practices known for increasing Evolvability. If, for example, you believe high automated test coverage helps Evolvability by lowering the fear of inadverted damage to a code base, why isn´t 90% of the developer community practicing automated tests consistently? I think, the answer is simple: Because they can do without. Somehow they manage to do enough manual checks before their rare releases/acceptance checks to ensure good enough correctness - at least in the short term. The same goes for other practices like component orientation, continuous build/integration, code reviews etc. None of that is compelling, urgent, imperative. Something else always seems more important. So Evolvability principles and practices fall through the cracks most of the time - until a project hits a wall. Then everybody becomes desperate; but by then (re)gaining Evolvability has become as very, very difficult and tedious undertaking. Sometimes up to the point where the existence of a project/company is in danger. With Spinning that´s different. If you´re practicing Spinning you cannot avoid all those practices. With Spinning you very quickly realize you cannot deliver reliably even on your 32 hour promises. Spinning thus is pulling on developers to adopt principles and practices for Evolvability. They will start actively looking for ways to keep their delivery rate high. And if not, management will soon tell them to do that. Because first the Product Owner then management will notice an increasing difficulty to deliver value within 32 hours. There, finally there emerges a way to measure Evolvability: The more frequent developers tell the Product Owner there is no way to deliver anything worth of feedback until tomorrow night, the poorer Evolvability is. Don´t count the “WTF!”, count the “No way!” utterances. In closing For sustainable software development we need to put Evolvability first. Functionality and Quality must not rule software development but be implemented within a framework ensuring (enough) Evolvability. Since Evolvability cannot be measured easily, I think we need to put software development “under pressure”. Software needs to be changed more often, in smaller increments. Each increment being relevant to the customer/user in some way. That does not mean each increment is worthy of shipment. It´s sufficient to gain further insight from it. Increments primarily serve the reduction of uncertainty, not sales. Sales even needs to be decoupled from this incremental progress. No more promises to sales. No more delivery au point. Rather sales should look at a stream of accepted increments (or incremental releases) and scoup from that whatever they find valuable. Sales and marketing need to realize they should work on what´s there, not what might be possible in the future. But I digress… In my view a Spinning cycle - which is not easy to reach, which requires practice - is the core practice to compensate the immeasurability of Evolvability. From start to finish of each issue in 32 hours max - that´s the challenge we need to accept if we´re serious increasing Evolvability. Fortunately higher Evolvability is not the only outcome of Spinning. Customer/management will like the increased flexibility and “getting more bang for the buck”.

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  • Scaling-out Your Services by Message Bus based WCF Transport Extension &ndash; Part 1 &ndash; Background

    - by Shaun
    Cloud computing gives us more flexibility on the computing resource, we can provision and deploy an application or service with multiple instances over multiple machines. With the increment of the service instances, how to balance the incoming message and workload would become a new challenge. Currently there are two approaches we can use to pass the incoming messages to the service instances, I would like call them dispatcher mode and pulling mode.   Dispatcher Mode The dispatcher mode introduces a role which takes the responsible to find the best service instance to process the request. The image below describes the sharp of this mode. There are four clients communicate with the service through the underlying transportation. For example, if we are using HTTP the clients might be connecting to the same service URL. On the server side there’s a dispatcher listening on this URL and try to retrieve all messages. When a message came in, the dispatcher will find a proper service instance to process it. There are three mechanism to find the instance: Round-robin: Dispatcher will always send the message to the next instance. For example, if the dispatcher sent the message to instance 2, then the next message will be sent to instance 3, regardless if instance 3 is busy or not at that moment. Random: Dispatcher will find a service instance randomly, and same as the round-robin mode it regardless if the instance is busy or not. Sticky: Dispatcher will send all related messages to the same service instance. This approach always being used if the service methods are state-ful or session-ful. But as you can see, all of these approaches are not really load balanced. The clients will send messages at any time, and each message might take different process duration on the server side. This means in some cases, some of the service instances are very busy while others are almost idle. For example, if we were using round-robin mode, it could be happened that most of the simple task messages were passed to instance 1 while the complex ones were sent to instance 3, even though instance 1 should be idle. This brings some problem in our architecture. The first one is that, the response to the clients might be longer than it should be. As it’s shown in the figure above, message 6 and 9 can be processed by instance 1 or instance 2, but in reality they were dispatched to the busy instance 3 since the dispatcher and round-robin mode. Secondly, if there are many requests came from the clients in a very short period, service instances might be filled by tons of pending tasks and some instances might be crashed. Third, if we are using some cloud platform to host our service instances, for example the Windows Azure, the computing resource is billed by service deployment period instead of the actual CPU usage. This means if any service instance is idle it is wasting our money! Last one, the dispatcher would be the bottleneck of our system since all incoming messages must be routed by the dispatcher. If we are using HTTP or TCP as the transport, the dispatcher would be a network load balance. If we wants more capacity, we have to scale-up, or buy a hardware load balance which is very expensive, as well as scaling-out the service instances. Pulling Mode Pulling mode doesn’t need a dispatcher to route the messages. All service instances are listening to the same transport and try to retrieve the next proper message to process if they are idle. Since there is no dispatcher in pulling mode, it requires some features on the transportation. The transportation must support multiple client connection and server listening. HTTP and TCP doesn’t allow multiple clients are listening on the same address and port, so it cannot be used in pulling mode directly. All messages in the transportation must be FIFO, which means the old message must be received before the new one. Message selection would be a plus on the transportation. This means both service and client can specify some selection criteria and just receive some specified kinds of messages. This feature is not mandatory but would be very useful when implementing the request reply and duplex WCF channel modes. Otherwise we must have a memory dictionary to store the reply messages. I will explain more about this in the following articles. Message bus, or the message queue would be best candidate as the transportation when using the pulling mode. First, it allows multiple application to listen on the same queue, and it’s FIFO. Some of the message bus also support the message selection, such as TIBCO EMS, RabbitMQ. Some others provide in memory dictionary which can store the reply messages, for example the Redis. The principle of pulling mode is to let the service instances self-managed. This means each instance will try to retrieve the next pending incoming message if they finished the current task. This gives us more benefit and can solve the problems we met with in the dispatcher mode. The incoming message will be received to the best instance to process, which means this will be very balanced. And it will not happen that some instances are busy while other are idle, since the idle one will retrieve more tasks to make them busy. Since all instances are try their best to be busy we can use less instances than dispatcher mode, which more cost effective. Since there’s no dispatcher in the system, there is no bottleneck. When we introduced more service instances, in dispatcher mode we have to change something to let the dispatcher know the new instances. But in pulling mode since all service instance are self-managed, there no extra change at all. If there are many incoming messages, since the message bus can queue them in the transportation, service instances would not be crashed. All above are the benefits using the pulling mode, but it will introduce some problem as well. The process tracking and debugging become more difficult. Since the service instances are self-managed, we cannot know which instance will process the message. So we need more information to support debug and track. Real-time response may not be supported. All service instances will process the next message after the current one has done, if we have some real-time request this may not be a good solution. Compare with the Pros and Cons above, the pulling mode would a better solution for the distributed system architecture. Because what we need more is the scalability, cost-effect and the self-management.   WCF and WCF Transport Extensibility Windows Communication Foundation (WCF) is a framework for building service-oriented applications. In the .NET world WCF is the best way to implement the service. In this series I’m going to demonstrate how to implement the pulling mode on top of a message bus by extending the WCF. I don’t want to deep into every related field in WCF but will highlight its transport extensibility. When we implemented an RPC foundation there are many aspects we need to deal with, for example the message encoding, encryption, authentication and message sending and receiving. In WCF, each aspect is represented by a channel. A message will be passed through all necessary channels and finally send to the underlying transportation. And on the other side the message will be received from the transport and though the same channels until the business logic. This mode is called “Channel Stack” in WCF, and the last channel in the channel stack must always be a transport channel, which takes the responsible for sending and receiving the messages. As we are going to implement the WCF over message bus and implement the pulling mode scaling-out solution, we need to create our own transport channel so that the client and service can exchange messages over our bus. Before we deep into the transport channel, let’s have a look on the message exchange patterns that WCF defines. Message exchange pattern (MEP) defines how client and service exchange the messages over the transportation. WCF defines 3 basic MEPs which are datagram, Request-Reply and Duplex. Datagram: Also known as one-way, or fire-forgot mode. The message sent from the client to the service, and no need any reply from the service. The client doesn’t care about the message result at all. Request-Reply: Very common used pattern. The client send the request message to the service and wait until the reply message comes from the service. Duplex: The client sent message to the service, when the service processing the message it can callback to the client. When callback the service would be like a client while the client would be like a service. In WCF, each MEP represent some channels associated. MEP Channels Datagram IInputChannel, IOutputChannel Request-Reply IRequestChannel, IReplyChannel Duplex IDuplexChannel And the channels are created by ChannelListener on the server side, and ChannelFactory on the client side. The ChannelListener and ChannelFactory are created by the TransportBindingElement. The TransportBindingElement is created by the Binding, which can be defined as a new binding or from a custom binding. For more information about the transport channel mode, please refer to the MSDN document. The figure below shows the transport channel objects when using the request-reply MEP. And this is the datagram MEP. And this is the duplex MEP. After investigated the WCF transport architecture, channel mode and MEP, we finally identified what we should do to extend our message bus based transport layer. They are: Binding: (Optional) Defines the channel elements in the channel stack and added our transport binding element at the bottom of the stack. But we can use the build-in CustomBinding as well. TransportBindingElement: Defines which MEP is supported in our transport and create the related ChannelListener and ChannelFactory. This also defines the scheme of the endpoint if using this transport. ChannelListener: Create the server side channel based on the MEP it’s. We can have one ChannelListener to create channels for all supported MEPs, or we can have ChannelListener for each MEP. In this series I will use the second approach. ChannelFactory: Create the client side channel based on the MEP it’s. We can have one ChannelFactory to create channels for all supported MEPs, or we can have ChannelFactory for each MEP. In this series I will use the second approach. Channels: Based on the MEPs we want to support, we need to implement the channels accordingly. For example, if we want our transport support Request-Reply mode we should implement IRequestChannel and IReplyChannel. In this series I will implement all 3 MEPs listed above one by one. Scaffold: In order to make our transport extension works we also need to implement some scaffold stuff. For example we need some classes to send and receive message though out message bus. We also need some codes to read and write the WCF message, etc.. These are not necessary but would be very useful in our example.   Message Bus There is only one thing remained before we can begin to implement our scaling-out support WCF transport, which is the message bus. As I mentioned above, the message bus must have some features to fulfill all the WCF MEPs. In my company we will be using TIBCO EMS, which is an enterprise message bus product. And I have said before we can use any message bus production if it’s satisfied with our requests. Here I would like to introduce an interface to separate the message bus from the WCF. This allows us to implement the bus operations by any kinds bus we are going to use. The interface would be like this. 1: public interface IBus : IDisposable 2: { 3: string SendRequest(string message, bool fromClient, string from, string to = null); 4:  5: void SendReply(string message, bool fromClient, string replyTo); 6:  7: BusMessage Receive(bool fromClient, string replyTo); 8: } There are only three methods for the bus interface. Let me explain one by one. The SendRequest method takes the responsible for sending the request message into the bus. The parameters description are: message: The WCF message content. fromClient: Indicates if this message was came from the client. from: The channel ID that this message was sent from. The channel ID will be generated when any kinds of channel was created, which will be explained in the following articles. to: The channel ID that this message should be received. In Request-Reply and Duplex MEP this is necessary since the reply message must be received by the channel which sent the related request message. The SendReply method takes the responsible for sending the reply message. It’s very similar as the previous one but no “from” parameter. This is because it’s no need to reply a reply message again in any MEPs. The Receive method takes the responsible for waiting for a incoming message, includes the request message and specified reply message. It returned a BusMessage object, which contains some information about the channel information. The code of the BusMessage class is 1: public class BusMessage 2: { 3: public string MessageID { get; private set; } 4: public string From { get; private set; } 5: public string ReplyTo { get; private set; } 6: public string Content { get; private set; } 7:  8: public BusMessage(string messageId, string fromChannelId, string replyToChannelId, string content) 9: { 10: MessageID = messageId; 11: From = fromChannelId; 12: ReplyTo = replyToChannelId; 13: Content = content; 14: } 15: } Now let’s implement a message bus based on the IBus interface. Since I don’t want you to buy and install the TIBCO EMS or any other message bus products, I will implement an in process memory bus. This bus is only for test and sample purpose. It can only be used if the service and client are in the same process. Very straightforward. 1: public class InProcMessageBus : IBus 2: { 3: private readonly ConcurrentDictionary<Guid, InProcMessageEntity> _queue; 4: private readonly object _lock; 5:  6: public InProcMessageBus() 7: { 8: _queue = new ConcurrentDictionary<Guid, InProcMessageEntity>(); 9: _lock = new object(); 10: } 11:  12: public string SendRequest(string message, bool fromClient, string from, string to = null) 13: { 14: var entity = new InProcMessageEntity(message, fromClient, from, to); 15: _queue.TryAdd(entity.ID, entity); 16: return entity.ID.ToString(); 17: } 18:  19: public void SendReply(string message, bool fromClient, string replyTo) 20: { 21: var entity = new InProcMessageEntity(message, fromClient, null, replyTo); 22: _queue.TryAdd(entity.ID, entity); 23: } 24:  25: public BusMessage Receive(bool fromClient, string replyTo) 26: { 27: InProcMessageEntity e = null; 28: while (true) 29: { 30: lock (_lock) 31: { 32: var entity = _queue 33: .Where(kvp => kvp.Value.FromClient == fromClient && (kvp.Value.To == replyTo || string.IsNullOrWhiteSpace(kvp.Value.To))) 34: .FirstOrDefault(); 35: if (entity.Key != Guid.Empty && entity.Value != null) 36: { 37: _queue.TryRemove(entity.Key, out e); 38: } 39: } 40: if (e == null) 41: { 42: Thread.Sleep(100); 43: } 44: else 45: { 46: return new BusMessage(e.ID.ToString(), e.From, e.To, e.Content); 47: } 48: } 49: } 50:  51: public void Dispose() 52: { 53: } 54: } The InProcMessageBus stores the messages in the objects of InProcMessageEntity, which can take some extra information beside the WCF message itself. 1: public class InProcMessageEntity 2: { 3: public Guid ID { get; set; } 4: public string Content { get; set; } 5: public bool FromClient { get; set; } 6: public string From { get; set; } 7: public string To { get; set; } 8:  9: public InProcMessageEntity() 10: : this(string.Empty, false, string.Empty, string.Empty) 11: { 12: } 13:  14: public InProcMessageEntity(string content, bool fromClient, string from, string to) 15: { 16: ID = Guid.NewGuid(); 17: Content = content; 18: FromClient = fromClient; 19: From = from; 20: To = to; 21: } 22: }   Summary OK, now I have all necessary stuff ready. The next step would be implementing our WCF message bus transport extension. In this post I described two scaling-out approaches on the service side especially if we are using the cloud platform: dispatcher mode and pulling mode. And I compared the Pros and Cons of them. Then I introduced the WCF channel stack, channel mode and the transport extension part, and identified what we should do to create our own WCF transport extension, to let our WCF services using pulling mode based on a message bus. And finally I provided some classes that need to be used in the future posts that working against an in process memory message bus, for the demonstration purpose only. In the next post I will begin to implement the transport extension step by step.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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  • ANTS Memory Profiler 7.0 Review

    - by Michael B. McLaughlin
    (This is my first review as a part of the GeeksWithBlogs.net Influencers program. It’s a program in which I (and the others who have been selected for it) get the opportunity to check out new products and services and write reviews about them. We don’t get paid for this, but we do generally get to keep a copy of the software or retain an account for some period of time on the service that we review. In this case I received a copy of Red Gate Software’s ANTS Memory Profiler 7.0, which was released in January. I don’t have any upgrade rights nor is my review guided, restrained, influenced, or otherwise controlled by Red Gate or anyone else. But I do get to keep the software license. I will always be clear about what I received whenever I do a review – I leave it up to you to decide whether you believe I can be objective. I believe I can be. If I used something and really didn’t like it, keeping a copy of it wouldn’t be worth anything to me. In that case though, I would simply uninstall/deactivate/whatever the software or service and tell the company what I didn’t like about it so they could (hopefully) make it better in the future. I don’t think it’d be polite to write up a terrible review, nor do I think it would be a particularly good use of my time. There are people who get paid for a living to review things, so I leave it to them to tell you what they think is bad and why. I’ll only spend my time telling you about things I think are good.) Overview of Common .NET Memory Problems When coming to land of managed memory from the wilds of unmanaged code, it’s easy to say to one’s self, “Wow! Now I never have to worry about memory problems again!” But this simply isn’t true. Managed code environments, such as .NET, make many, many things easier. You will never have to worry about memory corruption due to a bad pointer, for example (unless you’re working with unsafe code, of course). But managed code has its own set of memory concerns. For example, failing to unsubscribe from events when you are done with them leaves the publisher of an event with a reference to the subscriber. If you eliminate all your own references to the subscriber, then that memory is effectively lost since the GC won’t delete it because of the publishing object’s reference. When the publishing object itself becomes subject to garbage collection then you’ll get that memory back finally, but that could take a very long time depending of the life of the publisher. Another common source of resource leaks is failing to properly release unmanaged resources. When writing a class that contains members that hold unmanaged resources (e.g. any of the Stream-derived classes, IsolatedStorageFile, most classes ending in “Reader” or “Writer”), you should always implement IDisposable, making sure to use a properly written Dispose method. And when you are using an instance of a class that implements IDisposable, you should always make sure to use a 'using' statement in order to ensure that the object’s unmanaged resources are disposed of properly. (A ‘using’ statement is a nicer, cleaner looking, and easier to use version of a try-finally block. The compiler actually translates it as though it were a try-finally block. Note that Code Analysis warning 2202 (CA2202) will often be triggered by nested using blocks. A properly written dispose method ensures that it only runs once such that calling dispose multiple times should not be a problem. Nonetheless, CA2202 exists and if you want to avoid triggering it then you should write your code such that only the innermost IDisposable object uses a ‘using’ statement, with any outer code making use of appropriate try-finally blocks instead). Then, of course, there are situations where you are operating in a memory-constrained environment or else you want to limit or even eliminate allocations within a certain part of your program (e.g. within the main game loop of an XNA game) in order to avoid having the GC run. On the Xbox 360 and Windows Phone 7, for example, for every 1 MB of heap allocations you make, the GC runs; the added time of a GC collection can cause a game to drop frames or run slowly thereby making it look bad. Eliminating allocations (or else minimizing them and calling an explicit Collect at an appropriate time) is a common way of avoiding this (the other way is to simplify your heap so that the GC’s latency is low enough not to cause performance issues). ANTS Memory Profiler 7.0 When the opportunity to review Red Gate’s recently released ANTS Memory Profiler 7.0 arose, I jumped at it. In order to review it, I was given a free copy (which does not include upgrade rights for future versions) which I am allowed to keep. For those of you who are familiar with ANTS Memory Profiler, you can find a list of new features and enhancements here. If you are an experienced .NET developer who is familiar with .NET memory management issues, ANTS Memory Profiler is great. More importantly still, if you are new to .NET development or you have no experience or limited experience with memory profiling, ANTS Memory Profiler is awesome. From the very beginning, it guides you through the process of memory profiling. If you’re experienced and just want dive in however, it doesn’t get in your way. The help items GAHSFLASHDAJLDJA are well designed and located right next to the UI controls so that they are easy to find without being intrusive. When you first launch it, it presents you with a “Getting Started” screen that contains links to “Memory profiling video tutorials”, “Strategies for memory profiling”, and the “ANTS Memory Profiler forum”. I’m normally the kind of person who looks at a screen like that only to find the “Don’t show this again” checkbox. Since I was doing a review, though, I decided I should examine them. I was pleasantly surprised. The overview video clocks in at three minutes and fifty seconds. It begins by showing you how to get started profiling an application. It explains that profiling is done by taking memory snapshots periodically while your program is running and then comparing them. ANTS Memory Profiler (I’m just going to call it “ANTS MP” from here) analyzes these snapshots in the background while your application is running. It briefly mentions a new feature in Version 7, a new API that give you the ability to trigger snapshots from within your application’s source code (more about this below). You can also, and this is the more common way you would do it, take a memory snapshot at any time from within the ANTS MP window by clicking the “Take Memory Snapshot” button in the upper right corner. The overview video goes on to demonstrate a basic profiling session on an application that pulls information from a database and displays it. It shows how to switch which snapshots you are comparing, explains the different sections of the Summary view and what they are showing, and proceeds to show you how to investigate memory problems using the “Instance Categorizer” to track the path from an object (or set of objects) to the GC’s root in order to find what things along the path are holding a reference to it/them. For a set of objects, you can then click on it and get the “Instance List” view. This displays all of the individual objects (including their individual sizes, values, etc.) of that type which share the same path to the GC root. You can then click on one of the objects to generate an “Instance Retention Graph” view. This lets you track directly up to see the reference chain for that individual object. In the overview video, it turned out that there was an event handler which was holding on to a reference, thereby keeping a large number of strings that should have been freed in memory. Lastly the video shows the “Class List” view, which lets you dig in deeply to find problems that might not have been clear when following the previous workflow. Once you have at least one memory snapshot you can begin analyzing. The main interface is in the “Analysis” tab. You can also switch to the “Session Overview” tab, which gives you several bar charts highlighting basic memory data about the snapshots you’ve taken. If you hover over the individual bars (and the individual colors in bars that have more than one), you will see a detailed text description of what the bar is representing visually. The Session Overview is good for a quick summary of memory usage and information about the different heaps. You are going to spend most of your time in the Analysis tab, but it’s good to remember that the Session Overview is there to give you some quick feedback on basic memory usage stats. As described above in the summary of the overview video, there is a certain natural workflow to the Analysis tab. You’ll spin up your application and take some snapshots at various times such as before and after clicking a button to open a window or before and after closing a window. Taking these snapshots lets you examine what is happening with memory. You would normally expect that a lot of memory would be freed up when closing a window or exiting a document. By taking snapshots before and after performing an action like that you can see whether or not the memory is really being freed. If you already know an area that’s giving you trouble, you can run your application just like normal until just before getting to that part and then you can take a few strategic snapshots that should help you pin down the problem. Something the overview didn’t go into is how to use the “Filters” section at the bottom of ANTS MP together with the Class List view in order to narrow things down. The video tutorials page has a nice 3 minute intro video called “How to use the filters”. It’s a nice introduction and covers some of the basics. I’m going to cover a bit more because I think they’re a really neat, really helpful feature. Large programs can bring up thousands of classes. Even simple programs can instantiate far more classes than you might realize. In a basic .NET 4 WPF application for example (and when I say basic, I mean just MainWindow.xaml with a button added to it), the unfiltered Class List view will have in excess of 1000 classes (my simple test app had anywhere from 1066 to 1148 classes depending on which snapshot I was using as the “Current” snapshot). This is amazing in some ways as it shows you how in stark detail just how immensely powerful the WPF framework is. But hunting through 1100 classes isn’t productive, no matter how cool it is that there are that many classes instantiated and doing all sorts of awesome things. Let’s say you wanted to examine just the classes your application contains source code for (in my simple example, that would be the MainWindow and App). Under “Basic Filters”, click on “Classes with source” under “Show only…”. Voilà. Down from 1070 classes in the snapshot I was using as “Current” to 2 classes. If you then click on a class’s name, it will show you (to the right of the class name) two little icon buttons. Hover over them and you will see that you can click one to view the Instance Categorizer for the class and another to view the Instance List for the class. You can also show classes based on which heap they live on. If you chose both a Baseline snapshot and a Current snapshot then you can use the “Comparing snapshots” filters to show only: “New objects”; “Surviving objects”; “Survivors in growing classes”; or “Zombie objects” (if you aren’t sure what one of these means, you can click the helpful “?” in a green circle icon to bring up a popup that explains them and provides context). Remember that your selection(s) under the “Show only…” heading will still apply, so you should update those selections to make sure you are seeing the view you want. There are also links under the “What is my memory problem?” heading that can help you diagnose the problems you are seeing including one for “I don’t know which kind I have” for situations where you know generally that your application has some problems but aren’t sure what the behavior you have been seeing (OutOfMemoryExceptions, continually growing memory usage, larger memory use than expected at certain points in the program). The Basic Filters are not the only filters there are. “Filter by Object Type” gives you the ability to filter by: “Objects that are disposable”; “Objects that are/are not disposed”; “Objects that are/are not GC roots” (GC roots are things like static variables); and “Objects that implement _______”. “Objects that implement” is particularly neat. Once you check the box, you can then add one or more classes and interfaces that an object must implement in order to survive the filtering. Lastly there is “Filter by Reference”, which gives you the option to pare down the list based on whether an object is “Kept in memory exclusively by” a particular item, a class/interface, or a namespace; whether an object is “Referenced by” one or more of those choices; and whether an object is “Never referenced by” one or more of those choices. Remember that filtering is cumulative, so anything you had set in one of the filter sections still remains in effect unless and until you go back and change it. There’s quite a bit more to ANTS MP – it’s a very full featured product – but I think I touched on all of the most significant pieces. You can use it to debug: a .NET executable; an ASP.NET web application (running on IIS); an ASP.NET web application (running on Visual Studio’s built-in web development server); a Silverlight 4 browser application; a Windows service; a COM+ server; and even something called an XBAP (local XAML browser application). You can also attach to a .NET 4 process to profile an application that’s already running. The startup screen also has a large number of “Charting Options” that let you adjust which statistics ANTS MP should collect. The default selection is a good, minimal set. It’s worth your time to browse through the charting options to examine other statistics that may also help you diagnose a particular problem. The more statistics ANTS MP collects, the longer it will take to collect statistics. So just turning everything on is probably a bad idea. But the option to selectively add in additional performance counters from the extensive list could be a very helpful thing for your memory profiling as it lets you see additional data that might provide clues about a particular problem that has been bothering you. ANTS MP integrates very nicely with all versions of Visual Studio that support plugins (i.e. all of the non-Express versions). Just note that if you choose “Profile Memory” from the “ANTS” menu that it will launch profiling for whichever project you have set as the Startup project. One quick tip from my experience so far using ANTS MP: if you want to properly understand your memory usage in an application you’ve written, first create an “empty” version of the type of project you are going to profile (a WPF application, an XNA game, etc.) and do a quick profiling session on that so that you know the baseline memory usage of the framework itself. By “empty” I mean just create a new project of that type in Visual Studio then compile it and run it with profiling – don’t do anything special or add in anything (except perhaps for any external libraries you’re planning to use). The first thing I tried ANTS MP out on was a demo XNA project of an editor that I’ve been working on for quite some time that involves a custom extension to XNA’s content pipeline. The first time I ran it and saw the unmanaged memory usage I was convinced I had some horrible bug that was creating extra copies of texture data (the demo project didn’t have a lot of texture data so when I saw a lot of unmanaged memory I instantly figured I was doing something wrong). Then I thought to run an empty project through and when I saw that the amount of unmanaged memory was virtually identical, it dawned on me that the CLR itself sits in unmanaged memory and that (thankfully) there was nothing wrong with my code! Quite a relief. Earlier, when discussing the overview video, I mentioned the API that lets you take snapshots from within your application. I gave it a quick trial and it’s very easy to integrate and make use of and is a really nice addition (especially for projects where you want to know what, if any, allocations there are in a specific, complicated section of code). The only concern I had was that if I hadn’t watched the overview video I might never have known it existed. Even then it took me five minutes of hunting around Red Gate’s website before I found the “Taking snapshots from your code" article that explains what DLL you need to add as a reference and what method of what class you should call in order to take an automatic snapshot (including the helpful warning to wrap it in a try-catch block since, under certain circumstances, it can raise an exception, such as trying to call it more than 5 times in 30 seconds. The difficulty in discovering and then finding information about the automatic snapshots API was one thing I thought could use improvement. Another thing I think would make it even better would be local copies of the webpages it links to. Although I’m generally always connected to the internet, I imagine there are more than a few developers who aren’t or who are behind very restrictive firewalls. For them (and for me, too, if my internet connection happens to be down), it would be nice to have those documents installed locally or to have the option to download an additional “documentation” package that would add local copies. Another thing that I wish could be easier to manage is the Filters area. Finding and setting individual filters is very easy as is understanding what those filter do. And breaking it up into three sections (basic, by object, and by reference) makes sense. But I could easily see myself running a long profiling session and forgetting that I had set some filter a long while earlier in a different filter section and then spending quite a bit of time trying to figure out why some problem that was clearly visible in the data wasn’t showing up in, e.g. the instance list before remembering to check all the filters for that one setting that was only culling a few things from view. Some sort of indicator icon next to the filter section names that appears you have at least one filter set in that area would be a nice visual clue to remind me that “oh yeah, I told it to only show objects on the Gen 2 heap! That’s why I’m not seeing those instances of the SuperMagic class!” Something that would be nice (but that Red Gate cannot really do anything about) would be if this could be used in Windows Phone 7 development. If Microsoft and Red Gate could work together to make this happen (even if just on the WP7 emulator), that would be amazing. Especially given the memory constraints that apps and games running on mobile devices need to work within, a good memory profiler would be a phenomenally helpful tool. If anyone at Microsoft reads this, it’d be really great if you could make something like that happen. Perhaps even a (subsidized) custom version just for WP7 development. (For XNA games, of course, you can create a Windows version of the game and use ANTS MP on the Windows version in order to get a better picture of your memory situation. For Silverlight on WP7, though, there’s quite a bit of educated guess work and WeakReference creation followed by forced collections in order to find the source of a memory problem.) The only other thing I found myself wanting was a “Back” button. Between my Windows Phone 7, Zune, and other things, I’ve grown very used to having a “back stack” that lets me just navigate back to where I came from. The ANTS MP interface is surprisingly easy to use given how much it lets you do, and once you start using it for any amount of time, you learn all of the different areas such that you know where to go. And it does remember the state of the areas you were previously in, of course. So if you go to, e.g., the Instance Retention Graph from the Class List and then return back to the Class List, it will remember which class you had selected and all that other state information. Still, a “Back” button would be a welcome addition to a future release. Bottom Line ANTS Memory Profiler is not an inexpensive tool. But my time is valuable. I can easily see ANTS MP saving me enough time tracking down memory problems to justify it on a cost basis. More importantly to me, knowing what is happening memory-wise in my programs and having the confidence that my code doesn’t have any hidden time bombs in it that will cause it to OOM if I leave it running for longer than I do when I spin it up real quickly for debugging or just to see how a new feature looks and feels is a good feeling. It’s a feeling that I like having and want to continue to have. I got the current version for free in order to review it. Having done so, I’ve now added it to my must-have tools and will gladly lay out the money for the next version when it comes out. It has a 14 day free trial, so if you aren’t sure if it’s right for you or if you think it seems interesting but aren’t really sure if it’s worth shelling out the money for it, give it a try.

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  • Much Ado About Nothing: Stub Objects

    - by user9154181
    The Solaris 11 link-editor (ld) contains support for a new type of object that we call a stub object. A stub object is a shared object, built entirely from mapfiles, that supplies the same linking interface as the real object, while containing no code or data. Stub objects cannot be executed — the runtime linker will kill any process that attempts to load one. However, you can link to a stub object as a dependency, allowing the stub to act as a proxy for the real version of the object. You may well wonder if there is a point to producing an object that contains nothing but linking interface. As it turns out, stub objects are very useful for building large bodies of code such as Solaris. In the last year, we've had considerable success in applying them to one of our oldest and thorniest build problems. In this discussion, I will describe how we came to invent these objects, and how we apply them to building Solaris. This posting explains where the idea for stub objects came from, and details our long and twisty journey from hallway idea to standard link-editor feature. I expect that these details are mainly of interest to those who work on Solaris and its makefiles, those who have done so in the past, and those who work with other similar bodies of code. A subsequent posting will omit the history and background details, and instead discuss how to build and use stub objects. If you are mainly interested in what stub objects are, and don't care about the underlying software war stories, I encourage you to skip ahead. The Long Road To Stubs This all started for me with an email discussion in May of 2008, regarding a change request that was filed in 2002, entitled: 4631488 lib/Makefile is too patient: .WAITs should be reduced This CR encapsulates a number of cronic issues with Solaris builds: We build Solaris with a parallel make (dmake) that tries to build as much of the code base in parallel as possible. There is a lot of code to build, and we've long made use of parallelized builds to get the job done quicker. This is even more important in today's world of massively multicore hardware. Solaris contains a large number of executables and shared objects. Executables depend on shared objects, and shared objects can depend on each other. Before you can build an object, you need to ensure that the objects it needs have been built. This implies a need for serialization, which is in direct opposition to the desire to build everying in parallel. To accurately build objects in the right order requires an accurate set of make rules defining the things that depend on each other. This sounds simple, but the reality is quite complex. In practice, having programmers explicitly specify these dependencies is a losing strategy: It's really hard to get right. It's really easy to get it wrong and never know it because things build anyway. Even if you get it right, it won't stay that way, because dependencies between objects can change over time, and make cannot help you detect such drifing. You won't know that you got it wrong until the builds break. That can be a long time after the change that triggered the breakage happened, making it hard to connect the cause and the effect. Usually this happens just before a release, when the pressure is on, its hard to think calmly, and there is no time for deep fixes. As a poor compromise, the libraries in core Solaris were built using a set of grossly incomplete hand written rules, supplemented with a number of dmake .WAIT directives used to group the libraries into sets of non-interacting groups that can be built in parallel because we think they don't depend on each other. From time to time, someone will suggest that we could analyze the built objects themselves to determine their dependencies and then generate make rules based on those relationships. This is possible, but but there are complications that limit the usefulness of that approach: To analyze an object, you have to build it first. This is a classic chicken and egg scenario. You could analyze the results of a previous build, but then you're not necessarily going to get accurate rules for the current code. It should be possible to build the code without having a built workspace available. The analysis will take time, and remember that we're constantly trying to make builds faster, not slower. By definition, such an approach will always be approximate, and therefore only incremantally more accurate than the hand written rules described above. The hand written rules are fast and cheap, while this idea is slow and complex, so we stayed with the hand written approach. Solaris was built that way, essentially forever, because these are genuinely difficult problems that had no easy answer. The makefiles were full of build races in which the right outcomes happened reliably for years until a new machine or a change in build server workload upset the accidental balance of things. After figuring out what had happened, you'd mutter "How did that ever work?", add another incomplete and soon to be inaccurate make dependency rule to the system, and move on. This was not a satisfying solution, as we tend to be perfectionists in the Solaris group, but we didn't have a better answer. It worked well enough, approximately. And so it went for years. We needed a different approach — a new idea to cut the Gordian Knot. In that discussion from May 2008, my fellow linker-alien Rod Evans had the initial spark that lead us to a game changing series of realizations: The link-editor is used to link objects together, but it only uses the ELF metadata in the object, consisting of symbol tables, ELF versioning sections, and similar data. Notably, it does not look at, or understand, the machine code that makes an object useful at runtime. If you had an object that only contained the ELF metadata for a dependency, but not the code or data, the link-editor would find it equally useful for linking, and would never know the difference. Call it a stub object. In the core Solaris OS, we require all objects to be built with a link-editor mapfile that describes all of its publically available functions and data. Could we build a stub object using the mapfile for the real object? It ought to be very fast to build stub objects, as there are no input objects to process. Unlike the real object, stub objects would not actually require any dependencies, and so, all of the stubs for the entire system could be built in parallel. When building the real objects, one could link against the stub objects instead of the real dependencies. This means that all the real objects can be built built in parallel too, without any serialization. We could replace a system that requires perfect makefile rules with a system that requires no ordering rules whatsoever. The results would be considerably more robust. We immediately realized that this idea had potential, but also that there were many details to sort out, lots of work to do, and that perhaps it wouldn't really pan out. As is often the case, it would be necessary to do the work and see how it turned out. Following that conversation, I set about trying to build a stub object. We determined that a faithful stub has to do the following: Present the same set of global symbols, with the same ELF versioning, as the real object. Functions are simple — it suffices to have a symbol of the right type, possibly, but not necessarily, referencing a null function in its text segment. Copy relocations make data more complicated to stub. The possibility of a copy relocation means that when you create a stub, the data symbols must have the actual size of the real data. Any error in this will go uncaught at link time, and will cause tragic failures at runtime that are very hard to diagnose. For reasons too obscure to go into here, involving tentative symbols, it is also important that the data reside in bss, or not, matching its placement in the real object. If the real object has more than one symbol pointing at the same data item, we call these aliased symbols. All data symbols in the stub object must exhibit the same aliasing as the real object. We imagined the stub library feature working as follows: A command line option to ld tells it to produce a stub rather than a real object. In this mode, only mapfiles are examined, and any object or shared libraries on the command line are are ignored. The extra information needed (function or data, size, and bss details) would be added to the mapfile. When building the real object instead of the stub, the extra information for building stubs would be validated against the resulting object to ensure that they match. In exploring these ideas, I immediately run headfirst into the reality of the original mapfile syntax, a subject that I would later write about as The Problem(s) With Solaris SVR4 Link-Editor Mapfiles. The idea of extending that poor language was a non-starter. Until a better mapfile syntax became available, which seemed unlikely in 2008, the solution could not involve extentions to the mapfile syntax. Instead, we cooked up the idea (hack) of augmenting mapfiles with stylized comments that would carry the necessary information. A typical definition might look like: # DATA(i386) __iob 0x3c0 # DATA(amd64,sparcv9) __iob 0xa00 # DATA(sparc) __iob 0x140 iob; A further problem then became clear: If we can't extend the mapfile syntax, then there's no good way to extend ld with an option to produce stub objects, and to validate them against the real objects. The idea of having ld read comments in a mapfile and parse them for content is an unacceptable hack. The entire point of comments is that they are strictly for the human reader, and explicitly ignored by the tool. Taking all of these speed bumps into account, I made a new plan: A perl script reads the mapfiles, generates some small C glue code to produce empty functions and data definitions, compiles and links the stub object from the generated glue code, and then deletes the generated glue code. Another perl script used after both objects have been built, to compare the real and stub objects, using data from elfdump, and validate that they present the same linking interface. By June 2008, I had written the above, and generated a stub object for libc. It was a useful prototype process to go through, and it allowed me to explore the ideas at a deep level. Ultimately though, the result was unsatisfactory as a basis for real product. There were so many issues: The use of stylized comments were fine for a prototype, but not close to professional enough for shipping product. The idea of having to document and support it was a large concern. The ideal solution for stub objects really does involve having the link-editor accept the same arguments used to build the real object, augmented with a single extra command line option. Any other solution, such as our prototype script, will require makefiles to be modified in deeper ways to support building stubs, and so, will raise barriers to converting existing code. A validation script that rederives what the linker knew when it built an object will always be at a disadvantage relative to the actual linker that did the work. A stub object should be identifyable as such. In the prototype, there was no tag or other metadata that would let you know that they weren't real objects. Being able to identify a stub object in this way means that the file command can tell you what it is, and that the runtime linker can refuse to try and run a program that loads one. At that point, we needed to apply this prototype to building Solaris. As you might imagine, the task of modifying all the makefiles in the core Solaris code base in order to do this is a massive task, and not something you'd enter into lightly. The quality of the prototype just wasn't good enough to justify that sort of time commitment, so I tabled the project, putting it on my list of long term things to think about, and moved on to other work. It would sit there for a couple of years. Semi-coincidentally, one of the projects I tacked after that was to create a new mapfile syntax for the Solaris link-editor. We had wanted to do something about the old mapfile syntax for many years. Others before me had done some paper designs, and a great deal of thought had already gone into the features it should, and should not have, but for various reasons things had never moved beyond the idea stage. When I joined Sun in late 2005, I got involved in reviewing those things and thinking about the problem. Now in 2008, fresh from relearning for the Nth time why the old mapfile syntax was a huge impediment to linker progress, it seemed like the right time to tackle the mapfile issue. Paving the way for proper stub object support was not the driving force behind that effort, but I certainly had them in mind as I moved forward. The new mapfile syntax, which we call version 2, integrated into Nevada build snv_135 in in February 2010: 6916788 ld version 2 mapfile syntax PSARC/2009/688 Human readable and extensible ld mapfile syntax In order to prove that the new mapfile syntax was adequate for general purpose use, I had also done an overhaul of the ON consolidation to convert all mapfiles to use the new syntax, and put checks in place that would ensure that no use of the old syntax would creep back in. That work went back into snv_144 in June 2010: 6916796 OSnet mapfiles should use version 2 link-editor syntax That was a big putback, modifying 517 files, adding 18 new files, and removing 110 old ones. I would have done this putback anyway, as the work was already done, and the benefits of human readable syntax are obvious. However, among the justifications listed in CR 6916796 was this We anticipate adding additional features to the new mapfile language that will be applicable to ON, and which will require all sharable object mapfiles to use the new syntax. I never explained what those additional features were, and no one asked. It was premature to say so, but this was a reference to stub objects. By that point, I had already put together a working prototype link-editor with the necessary support for stub objects. I was pleased to find that building stubs was indeed very fast. On my desktop system (Ultra 24), an amd64 stub for libc can can be built in a fraction of a second: % ptime ld -64 -z stub -o stubs/libc.so.1 -G -hlibc.so.1 \ -ztext -zdefs -Bdirect ... real 0.019708910 user 0.010101680 sys 0.008528431 In order to go from prototype to integrated link-editor feature, I knew that I would need to prove that stub objects were valuable. And to do that, I knew that I'd have to switch the Solaris ON consolidation to use stub objects and evaluate the outcome. And in order to do that experiment, ON would first need to be converted to version 2 mapfiles. Sub-mission accomplished. Normally when you design a new feature, you can devise reasonably small tests to show it works, and then deploy it incrementally, letting it prove its value as it goes. The entire point of stub objects however was to demonstrate that they could be successfully applied to an extremely large and complex code base, and specifically to solve the Solaris build issues detailed above. There was no way to finesse the matter — in order to move ahead, I would have to successfully use stub objects to build the entire ON consolidation and demonstrate their value. In software, the need to boil the ocean can often be a warning sign that things are trending in the wrong direction. Conversely, sometimes progress demands that you build something large and new all at once. A big win, or a big loss — sometimes all you can do is try it and see what happens. And so, I spent some time staring at ON makefiles trying to get a handle on how things work, and how they'd have to change. It's a big and messy world, full of complex interactions, unspecified dependencies, special cases, and knowledge of arcane makefile features... ...and so, I backed away, put it down for a few months and did other work... ...until the fall, when I felt like it was time to stop thinking and pondering (some would say stalling) and get on with it. Without stubs, the following gives a simplified high level view of how Solaris is built: An initially empty directory known as the proto, and referenced via the ROOT makefile macro is established to receive the files that make up the Solaris distribution. A top level setup rule creates the proto area, and performs operations needed to initialize the workspace so that the main build operations can be launched, such as copying needed header files into the proto area. Parallel builds are launched to build the kernel (usr/src/uts), libraries (usr/src/lib), and commands. The install makefile target builds each item and delivers a copy to the proto area. All libraries and executables link against the objects previously installed in the proto, implying the need to synchronize the order in which things are built. Subsequent passes run lint, and do packaging. Given this structure, the additions to use stub objects are: A new second proto area is established, known as the stub proto and referenced via the STUBROOT makefile macro. The stub proto has the same structure as the real proto, but is used to hold stub objects. All files in the real proto are delivered as part of the Solaris product. In contrast, the stub proto is used to build the product, and then thrown away. A new target is added to library Makefiles called stub. This rule builds the stub objects. The ld command is designed so that you can build a stub object using the same ld command line you'd use to build the real object, with the addition of a single -z stub option. This means that the makefile rules for building the stub objects are very similar to those used to build the real objects, and many existing makefile definitions can be shared between them. A new target is added to the Makefiles called stubinstall which delivers the stub objects built by the stub rule into the stub proto. These rules reuse much of existing plumbing used by the existing install rule. The setup rule runs stubinstall over the entire lib subtree as part of its initialization. All libraries and executables link against the objects in the stub proto rather than the main proto, and can therefore be built in parallel without any synchronization. There was no small way to try this that would yield meaningful results. I would have to take a leap of faith and edit approximately 1850 makefiles and 300 mapfiles first, trusting that it would all work out. Once the editing was done, I'd type make and see what happened. This took about 6 weeks to do, and there were many dark days when I'd question the entire project, or struggle to understand some of the many twisted and complex situations I'd uncover in the makefiles. I even found a couple of new issues that required changes to the new stub object related code I'd added to ld. With a substantial amount of encouragement and help from some key people in the Solaris group, I eventually got the editing done and stub objects for the entire workspace built. I found that my desktop system could build all the stub objects in the workspace in roughly a minute. This was great news, as it meant that use of the feature is effectively free — no one was likely to notice or care about the cost of building them. After another week of typing make, fixing whatever failed, and doing it again, I succeeded in getting a complete build! The next step was to remove all of the make rules and .WAIT statements dedicated to controlling the order in which libraries under usr/src/lib are built. This came together pretty quickly, and after a few more speed bumps, I had a workspace that built cleanly and looked like something you might actually be able to integrate someday. This was a significant milestone, but there was still much left to do. I turned to doing full nightly builds. Every type of build (open, closed, OpenSolaris, export, domestic) had to be tried. Each type failed in a new and unique way, requiring some thinking and rework. As things came together, I became aware of things that could have been done better, simpler, or cleaner, and those things also required some rethinking, the seeking of wisdom from others, and some rework. After another couple of weeks, it was in close to final form. My focus turned towards the end game and integration. This was a huge workspace, and needed to go back soon, before changes in the gate would made merging increasingly difficult. At this point, I knew that the stub objects had greatly simplified the makefile logic and uncovered a number of race conditions, some of which had been there for years. I assumed that the builds were faster too, so I did some builds intended to quantify the speedup in build time that resulted from this approach. It had never occurred to me that there might not be one. And so, I was very surprised to find that the wall clock build times for a stock ON workspace were essentially identical to the times for my stub library enabled version! This is why it is important to always measure, and not just to assume. One can tell from first principles, based on all those removed dependency rules in the library makefile, that the stub object version of ON gives dmake considerably more opportunities to overlap library construction. Some hypothesis were proposed, and shot down: Could we have disabled dmakes parallel feature? No, a quick check showed things being build in parallel. It was suggested that we might be I/O bound, and so, the threads would be mostly idle. That's a plausible explanation, but system stats didn't really support it. Plus, the timing between the stub and non-stub cases were just too suspiciously identical. Are our machines already handling as much parallelism as they are capable of, and unable to exploit these additional opportunities? Once again, we didn't see the evidence to back this up. Eventually, a more plausible and obvious reason emerged: We build the libraries and commands (usr/src/lib, usr/src/cmd) in parallel with the kernel (usr/src/uts). The kernel is the long leg in that race, and so, wall clock measurements of build time are essentially showing how long it takes to build uts. Although it would have been nice to post a huge speedup immediately, we can take solace in knowing that stub objects simplify the makefiles and reduce the possibility of race conditions. The next step in reducing build time should be to find ways to reduce or overlap the uts part of the builds. When that leg of the build becomes shorter, then the increased parallelism in the libs and commands will pay additional dividends. Until then, we'll just have to settle for simpler and more robust. And so, I integrated the link-editor support for creating stub objects into snv_153 (November 2010) with 6993877 ld should produce stub objects PSARC/2010/397 ELF Stub Objects followed by the work to convert the ON consolidation in snv_161 (February 2011) with 7009826 OSnet should use stub objects 4631488 lib/Makefile is too patient: .WAITs should be reduced This was a huge putback, with 2108 modified files, 8 new files, and 2 removed files. Due to the size, I was allowed a window after snv_160 closed in which to do the putback. It went pretty smoothly for something this big, a few more preexisting race conditions would be discovered and addressed over the next few weeks, and things have been quiet since then. Conclusions and Looking Forward Solaris has been built with stub objects since February. The fact that developers no longer specify the order in which libraries are built has been a big success, and we've eliminated an entire class of build error. That's not to say that there are no build races left in the ON makefiles, but we've taken a substantial bite out of the problem while generally simplifying and improving things. The introduction of a stub proto area has also opened some interesting new possibilities for other build improvements. As this article has become quite long, and as those uses do not involve stub objects, I will defer that discussion to a future article.

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  • Using the ASP.NET Cache to cache data in a Model or Business Object layer, without a dependency on System.Web in the layer - Part One.

    - by Rhames
    ASP.NET applications can make use of the System.Web.Caching.Cache object to cache data and prevent repeated expensive calls to a database or other store. However, ideally an application should make use of caching at the point where data is retrieved from the database, which typically is inside a Business Objects or Model layer. One of the key features of using a UI pattern such as Model-View-Presenter (MVP) or Model-View-Controller (MVC) is that the Model and Presenter (or Controller) layers are developed without any knowledge of the UI layer. Introducing a dependency on System.Web into the Model layer would break this independence of the Model from the View. This article gives a solution to this problem, using dependency injection to inject the caching implementation into the Model layer at runtime. This allows caching to be used within the Model layer, without any knowledge of the actual caching mechanism that will be used. Create a sample application to use the caching solution Create a test SQL Server database This solution uses a SQL Server database with the same Sales data used in my previous post on calculating running totals. The advantage of using this data is that it gives nice slow queries that will exaggerate the effect of using caching! To create the data, first create a new SQL database called CacheSample. Next run the following script to create the Sale table and populate it: USE CacheSample GO   CREATE TABLE Sale(DayCount smallint, Sales money) CREATE CLUSTERED INDEX ndx_DayCount ON Sale(DayCount) go INSERT Sale VALUES (1,120) INSERT Sale VALUES (2,60) INSERT Sale VALUES (3,125) INSERT Sale VALUES (4,40)   DECLARE @DayCount smallint, @Sales money SET @DayCount = 5 SET @Sales = 10   WHILE @DayCount < 5000  BEGIN  INSERT Sale VALUES (@DayCount,@Sales)  SET @DayCount = @DayCount + 1  SET @Sales = @Sales + 15  END Next create a stored procedure to calculate the running total, and return a specified number of rows from the Sale table, using the following script: USE [CacheSample] GO   SET ANSI_NULLS ON GO   SET QUOTED_IDENTIFIER ON GO   -- ============================================= -- Author:        Robin -- Create date: -- Description:   -- ============================================= CREATE PROCEDURE [dbo].[spGetRunningTotals]       -- Add the parameters for the stored procedure here       @HighestDayCount smallint = null AS BEGIN       -- SET NOCOUNT ON added to prevent extra result sets from       -- interfering with SELECT statements.       SET NOCOUNT ON;         IF @HighestDayCount IS NULL             SELECT @HighestDayCount = MAX(DayCount) FROM dbo.Sale                   DECLARE @SaleTbl TABLE (DayCount smallint, Sales money, RunningTotal money)         DECLARE @DayCount smallint,                   @Sales money,                   @RunningTotal money         SET @RunningTotal = 0       SET @DayCount = 0         DECLARE rt_cursor CURSOR       FOR       SELECT DayCount, Sales       FROM Sale       ORDER BY DayCount         OPEN rt_cursor         FETCH NEXT FROM rt_cursor INTO @DayCount,@Sales         WHILE @@FETCH_STATUS = 0 AND @DayCount <= @HighestDayCount        BEGIN        SET @RunningTotal = @RunningTotal + @Sales        INSERT @SaleTbl VALUES (@DayCount,@Sales,@RunningTotal)        FETCH NEXT FROM rt_cursor INTO @DayCount,@Sales        END         CLOSE rt_cursor       DEALLOCATE rt_cursor         SELECT DayCount, Sales, RunningTotal       FROM @SaleTbl   END   GO   Create the Sample ASP.NET application In Visual Studio create a new solution and add a class library project called CacheSample.BusinessObjects and an ASP.NET web application called CacheSample.UI. The CacheSample.BusinessObjects project will contain a single class to represent a Sale data item, with all the code to retrieve the sales from the database included in it for simplicity (normally I would at least have a separate Repository or other object that is responsible for retrieving data, and probably a data access layer as well, but for this sample I want to keep it simple). The C# code for the Sale class is shown below: using System; using System.Collections.Generic; using System.Data; using System.Data.SqlClient;   namespace CacheSample.BusinessObjects {     public class Sale     {         public Int16 DayCount { get; set; }         public decimal Sales { get; set; }         public decimal RunningTotal { get; set; }           public static IEnumerable<Sale> GetSales(int? highestDayCount)         {             List<Sale> sales = new List<Sale>();               SqlParameter highestDayCountParameter = new SqlParameter("@HighestDayCount", SqlDbType.SmallInt);             if (highestDayCount.HasValue)                 highestDayCountParameter.Value = highestDayCount;             else                 highestDayCountParameter.Value = DBNull.Value;               string connectionStr = System.Configuration.ConfigurationManager .ConnectionStrings["CacheSample"].ConnectionString;               using(SqlConnection sqlConn = new SqlConnection(connectionStr))             using (SqlCommand sqlCmd = sqlConn.CreateCommand())             {                 sqlCmd.CommandText = "spGetRunningTotals";                 sqlCmd.CommandType = CommandType.StoredProcedure;                 sqlCmd.Parameters.Add(highestDayCountParameter);                   sqlConn.Open();                   using (SqlDataReader dr = sqlCmd.ExecuteReader())                 {                     while (dr.Read())                     {                         Sale newSale = new Sale();                         newSale.DayCount = dr.GetInt16(0);                         newSale.Sales = dr.GetDecimal(1);                         newSale.RunningTotal = dr.GetDecimal(2);                           sales.Add(newSale);                     }                 }             }               return sales;         }     } }   The static GetSale() method makes a call to the spGetRunningTotals stored procedure and then reads each row from the returned SqlDataReader into an instance of the Sale class, it then returns a List of the Sale objects, as IEnnumerable<Sale>. A reference to System.Configuration needs to be added to the CacheSample.BusinessObjects project so that the connection string can be read from the web.config file. In the CacheSample.UI ASP.NET project, create a single web page called ShowSales.aspx, and make this the default start up page. This page will contain a single button to call the GetSales() method and a label to display the results. The html mark up and the C# code behind are shown below: ShowSales.aspx <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="ShowSales.aspx.cs" Inherits="CacheSample.UI.ShowSales" %>   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">   <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server">     <title>Cache Sample - Show All Sales</title> </head> <body>     <form id="form1" runat="server">     <div>         <asp:Button ID="btnTest1" runat="server" onclick="btnTest1_Click"             Text="Get All Sales" />         &nbsp;&nbsp;&nbsp;         <asp:Label ID="lblResults" runat="server"></asp:Label>         </div>     </form> </body> </html>   ShowSales.aspx.cs using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls;   using CacheSample.BusinessObjects;   namespace CacheSample.UI {     public partial class ShowSales : System.Web.UI.Page     {         protected void Page_Load(object sender, EventArgs e)         {         }           protected void btnTest1_Click(object sender, EventArgs e)         {             System.Diagnostics.Stopwatch stopWatch = new System.Diagnostics.Stopwatch();             stopWatch.Start();               var sales = Sale.GetSales(null);               var lastSales = sales.Last();               stopWatch.Stop();               lblResults.Text = string.Format( "Count of Sales: {0}, Last DayCount: {1}, Total Sales: {2}. Query took {3} ms", sales.Count(), lastSales.DayCount, lastSales.RunningTotal, stopWatch.ElapsedMilliseconds);         }       } }   Finally we need to add a connection string to the CacheSample SQL Server database, called CacheSample, to the web.config file: <?xmlversion="1.0"?>   <configuration>    <connectionStrings>     <addname="CacheSample"          connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;Initial Catalog=CacheSample"          providerName="System.Data.SqlClient" />  </connectionStrings>    <system.web>     <compilationdebug="true"targetFramework="4.0" />  </system.web>   </configuration>   Run the application and click the button a few times to see how long each call to the database takes. On my system, each query takes about 450ms. Next I shall look at a solution to use the ASP.NET caching to cache the data returned by the query, so that subsequent requests to the GetSales() method are much faster. Adding Data Caching Support I am going to create my caching support in a separate project called CacheSample.Caching, so the next step is to add a class library to the solution. We shall be using the application configuration to define the implementation of our caching system, so we need a reference to System.Configuration adding to the project. ICacheProvider<T> Interface The first step in adding caching to our application is to define an interface, called ICacheProvider, in the CacheSample.Caching project, with methods to retrieve any data from the cache or to retrieve the data from the data source if it is not present in the cache. Dependency Injection will then be used to inject an implementation of this interface at runtime, allowing the users of the interface (i.e. the CacheSample.BusinessObjects project) to be completely unaware of how the caching is actually implemented. As data of any type maybe retrieved from the data source, it makes sense to use generics in the interface, with a generic type parameter defining the data type associated with a particular instance of the cache interface implementation. The C# code for the ICacheProvider interface is shown below: using System; using System.Collections.Generic;   namespace CacheSample.Caching {     public interface ICacheProvider     {     }       public interface ICacheProvider<T> : ICacheProvider     {         T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry);           IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry);     } }   The empty non-generic interface will be used as a type in a Dictionary generic collection later to store instances of the ICacheProvider<T> implementation for reuse, I prefer to use a base interface when doing this, as I think the alternative of using object makes for less clear code. The ICacheProvider<T> interface defines two overloaded Fetch methods, the difference between these is that one will return a single instance of the type T and the other will return an IEnumerable<T>, providing support for easy caching of collections of data items. Both methods will take a key parameter, which will uniquely identify the cached data, a delegate of type Func<T> or Func<IEnumerable<T>> which will provide the code to retrieve the data from the store if it is not present in the cache, and absolute or relative expiry policies to define when a cached item should expire. Note that at present there is no support for cache dependencies, but I shall be showing a method of adding this in part two of this article. CacheProviderFactory Class We need a mechanism of creating instances of our ICacheProvider<T> interface, using Dependency Injection to get the implementation of the interface. To do this we shall create a CacheProviderFactory static class in the CacheSample.Caching project. This factory will provide a generic static method called GetCacheProvider<T>(), which shall return instances of ICacheProvider<T>. We can then call this factory method with the relevant data type (for example the Sale class in the CacheSample.BusinessObject project) to get a instance of ICacheProvider for that type (e.g. call CacheProviderFactory.GetCacheProvider<Sale>() to get the ICacheProvider<Sale> implementation). The C# code for the CacheProviderFactory is shown below: using System; using System.Collections.Generic;   using CacheSample.Caching.Configuration;   namespace CacheSample.Caching {     public static class CacheProviderFactory     {         private static Dictionary<Type, ICacheProvider> cacheProviders = new Dictionary<Type, ICacheProvider>();         private static object syncRoot = new object();           ///<summary>         /// Factory method to create or retrieve an implementation of the  /// ICacheProvider interface for type <typeparamref name="T"/>.         ///</summary>         ///<typeparam name="T">  /// The type that this cache provider instance will work with  ///</typeparam>         ///<returns>An instance of the implementation of ICacheProvider for type  ///<typeparamref name="T"/>, as specified by the application  /// configuration</returns>         public static ICacheProvider<T> GetCacheProvider<T>()         {             ICacheProvider<T> cacheProvider = null;             // Get the Type reference for the type parameter T             Type typeOfT = typeof(T);               // Lock the access to the cacheProviders dictionary             // so multiple threads can work with it             lock (syncRoot)             {                 // First check if an instance of the ICacheProvider implementation  // already exists in the cacheProviders dictionary for the type T                 if (cacheProviders.ContainsKey(typeOfT))                     cacheProvider = (ICacheProvider<T>)cacheProviders[typeOfT];                 else                 {                     // There is not already an instance of the ICacheProvider in       // cacheProviders for the type T                     // so we need to create one                       // Get the Type reference for the application's implementation of       // ICacheProvider from the configuration                     Type cacheProviderType = Type.GetType(CacheProviderConfigurationSection.Current. CacheProviderType);                     if (cacheProviderType != null)                     {                         // Now get a Type reference for the Cache Provider with the                         // type T generic parameter                         Type typeOfCacheProviderTypeForT = cacheProviderType.MakeGenericType(new Type[] { typeOfT });                         if (typeOfCacheProviderTypeForT != null)                         {                             // Create the instance of the Cache Provider and add it to // the cacheProviders dictionary for future use                             cacheProvider = (ICacheProvider<T>)Activator. CreateInstance(typeOfCacheProviderTypeForT);                             cacheProviders.Add(typeOfT, cacheProvider);                         }                     }                 }             }               return cacheProvider;                 }     } }   As this code uses Activator.CreateInstance() to create instances of the ICacheProvider<T> implementation, which is a slow process, the factory class maintains a Dictionary of the previously created instances so that a cache provider needs to be created only once for each type. The type of the implementation of ICacheProvider<T> is read from a custom configuration section in the application configuration file, via the CacheProviderConfigurationSection class, which is described below. CacheProviderConfigurationSection Class The implementation of ICacheProvider<T> will be specified in a custom configuration section in the application’s configuration. To handle this create a folder in the CacheSample.Caching project called Configuration, and add a class called CacheProviderConfigurationSection to this folder. This class will extend the System.Configuration.ConfigurationSection class, and will contain a single string property called CacheProviderType. The C# code for this class is shown below: using System; using System.Configuration;   namespace CacheSample.Caching.Configuration {     internal class CacheProviderConfigurationSection : ConfigurationSection     {         public static CacheProviderConfigurationSection Current         {             get             {                 return (CacheProviderConfigurationSection) ConfigurationManager.GetSection("cacheProvider");             }         }           [ConfigurationProperty("type", IsRequired=true)]         public string CacheProviderType         {             get             {                 return (string)this["type"];             }         }     } }   Adding Data Caching to the Sales Class We now have enough code in place to add caching to the GetSales() method in the CacheSample.BusinessObjects.Sale class, even though we do not yet have an implementation of the ICacheProvider<T> interface. We need to add a reference to the CacheSample.Caching project to CacheSample.BusinessObjects so that we can use the ICacheProvider<T> interface within the GetSales() method. Once the reference is added, we can first create a unique string key based on the method name and the parameter value, so that the same cache key is used for repeated calls to the method with the same parameter values. Then we get an instance of the cache provider for the Sales type, using the CacheProviderFactory, and pass the existing code to retrieve the data from the database as the retrievalMethod delegate in a call to the Cache Provider Fetch() method. The C# code for the modified GetSales() method is shown below: public static IEnumerable<Sale> GetSales(int? highestDayCount) {     string cacheKey = string.Format("CacheSample.BusinessObjects.GetSalesWithCache({0})", highestDayCount);       return CacheSample.Caching.CacheProviderFactory. GetCacheProvider<Sale>().Fetch(cacheKey,         delegate()         {             List<Sale> sales = new List<Sale>();               SqlParameter highestDayCountParameter = new SqlParameter("@HighestDayCount", SqlDbType.SmallInt);             if (highestDayCount.HasValue)                 highestDayCountParameter.Value = highestDayCount;             else                 highestDayCountParameter.Value = DBNull.Value;               string connectionStr = System.Configuration.ConfigurationManager. ConnectionStrings["CacheSample"].ConnectionString;               using (SqlConnection sqlConn = new SqlConnection(connectionStr))             using (SqlCommand sqlCmd = sqlConn.CreateCommand())             {                 sqlCmd.CommandText = "spGetRunningTotals";                 sqlCmd.CommandType = CommandType.StoredProcedure;                 sqlCmd.Parameters.Add(highestDayCountParameter);                   sqlConn.Open();                   using (SqlDataReader dr = sqlCmd.ExecuteReader())                 {                     while (dr.Read())                     {                         Sale newSale = new Sale();                         newSale.DayCount = dr.GetInt16(0);                         newSale.Sales = dr.GetDecimal(1);                         newSale.RunningTotal = dr.GetDecimal(2);                           sales.Add(newSale);                     }                 }             }               return sales;         },         null,         new TimeSpan(0, 10, 0)); }     This example passes the code to retrieve the Sales data from the database to the Cache Provider as an anonymous method, however it could also be written as a lambda. The main advantage of using an anonymous function (method or lambda) is that the code inside the anonymous function can access the parameters passed to the GetSales() method. Finally the absolute expiry is set to null, and the relative expiry set to 10 minutes, to indicate that the cache entry should be removed 10 minutes after the last request for the data. As the ICacheProvider<T> has a Fetch() method that returns IEnumerable<T>, we can simply return the results of the Fetch() method to the caller of the GetSales() method. This should be all that is needed for the GetSales() method to now retrieve data from a cache after the first time the data has be retrieved from the database. Implementing a ASP.NET Cache Provider The final step is to actually implement the ICacheProvider<T> interface, and add the implementation details to the web.config file for the dependency injection. The cache provider implementation needs to have access to System.Web. Therefore it could be placed in the CacheSample.UI project, or in its own project that has a reference to System.Web. Implementing the Cache Provider in a separate project is my favoured approach. Create a new project inside the solution called CacheSample.CacheProvider, and add references to System.Web and CacheSample.Caching to this project. Add a class to the project called AspNetCacheProvider. Make the class a generic class by adding the generic parameter <T> and indicate that the class implements ICacheProvider<T>. The C# code for the AspNetCacheProvider class is shown below: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Caching;   using CacheSample.Caching;   namespace CacheSample.CacheProvider {     public class AspNetCacheProvider<T> : ICacheProvider<T>     {         #region ICacheProvider<T> Members           public T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry)         {             return FetchAndCache<T>(key, retrieveData, absoluteExpiry, relativeExpiry);         }           public IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry)         {             return FetchAndCache<IEnumerable<T>>(key, retrieveData, absoluteExpiry, relativeExpiry);         }           #endregion           #region Helper Methods           private U FetchAndCache<U>(string key, Func<U> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry)         {             U value;             if (!TryGetValue<U>(key, out value))             {                 value = retrieveData();                 if (!absoluteExpiry.HasValue)                     absoluteExpiry = Cache.NoAbsoluteExpiration;                   if (!relativeExpiry.HasValue)                     relativeExpiry = Cache.NoSlidingExpiration;                   HttpContext.Current.Cache.Insert(key, value, null, absoluteExpiry.Value, relativeExpiry.Value);             }             return value;         }           private bool TryGetValue<U>(string key, out U value)         {             object cachedValue = HttpContext.Current.Cache.Get(key);             if (cachedValue == null)             {                 value = default(U);                 return false;             }             else             {                 try                 {                     value = (U)cachedValue;                     return true;                 }                 catch                 {                     value = default(U);                     return false;                 }             }         }           #endregion       } }   The two interface Fetch() methods call a private method called FetchAndCache(). This method first checks for a element in the HttpContext.Current.Cache with the specified cache key, and if so tries to cast this to the specified type (either T or IEnumerable<T>). If the cached element is found, the FetchAndCache() method simply returns it. If it is not found in the cache, the method calls the retrievalMethod delegate to get the data from the data source, and then adds this to the HttpContext.Current.Cache. The final step is to add the AspNetCacheProvider class to the relevant custom configuration section in the CacheSample.UI.Web.Config file. To do this there needs to be a <configSections> element added as the first element in <configuration>. This will match a custom section called <cacheProvider> with the CacheProviderConfigurationSection. Then we add a <cacheProvider> element, with a type property set to the fully qualified assembly name of the AspNetCacheProvider class, as shown below: <?xmlversion="1.0"?>   <configuration>  <configSections>     <sectionname="cacheProvider" type="CacheSample.Base.Configuration.CacheProviderConfigurationSection, CacheSample.Base" />  </configSections>    <connectionStrings>     <addname="CacheSample"          connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;Initial Catalog=CacheSample"          providerName="System.Data.SqlClient" />  </connectionStrings>    <cacheProvidertype="CacheSample.CacheProvider.AspNetCacheProvider`1, CacheSample.CacheProvider, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">  </cacheProvider>    <system.web>     <compilationdebug="true"targetFramework="4.0" />  </system.web>   </configuration>   One point to note is that the fully qualified assembly name of the AspNetCacheProvider class includes the notation `1 after the class name, which indicates that it is a generic class with a single generic type parameter. The CacheSample.UI project needs to have references added to CacheSample.Caching and CacheSample.CacheProvider so that the actual application is aware of the relevant cache provider implementation. Conclusion After implementing this solution, you should have a working cache provider mechanism, that will allow the middle and data access layers to implement caching support when retrieving data, without any knowledge of the actually caching implementation. If the UI is not ASP.NET based, if for example it is Winforms or WPF, the implementation of ICacheProvider<T> would be written around whatever technology is available. It could even be a standalone caching system that takes full responsibility for adding and removing items from a global store. The next part of this article will show how this caching mechanism may be extended to provide support for cache dependencies, such as the System.Web.Caching.SqlCacheDependency. Another possible extension would be to cache the cache provider implementations instead of storing them in a static Dictionary in the CacheProviderFactory. This would prevent a build up of seldom used cache providers in the application memory, as they could be removed from the cache if not used often enough, although in reality there are probably unlikely to be vast numbers of cache provider implementation instances, as most applications do not have a massive number of business object or model types.

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  • Nagging As A Strategy For Better Linking: -z guidance

    - by user9154181
    The link-editor (ld) in Solaris 11 has a new feature that we call guidance that is intended to help you build better objects. The basic idea behind guidance is that if (and only if) you request it, the link-editor will issue messages suggesting better options and other changes you might make to your ld command to get better results. You can choose to take the advice, or you can disable specific types of guidance while acting on others. In some ways, this works like an experienced friend leaning over your shoulder and giving you advice — you're free to take it or leave it as you see fit, but you get nudged to do a better job than you might have otherwise. We use guidance to build the core Solaris OS, and it has proven to be useful, both in improving our objects, and in making sure that regressions don't creep back in later. In this article, I'm going to describe the evolution in thinking and design that led to the implementation of the -z guidance option, as well as give a brief description of how it works. The guidance feature issues non-fatal warnings. However, experience shows that once developers get used to ignoring warnings, it is inevitable that real problems will be lost in the noise and ignored or missed. This is why we have a zero tolerance policy against build noise in the core Solaris OS. In order to get maximum benefit from -z guidance while maintaining this policy, I added the -z fatal-warnings option at the same time. Much of the material presented here is adapted from the arc case: PSARC 2010/312 Link-editor guidance The History Of Unfortunate Link-Editor Defaults The Solaris link-editor is one of the oldest Unix commands. It stands to reason that this would be true — in order to write an operating system, you need the ability to compile and link code. The original link-editor (ld) had defaults that made sense at the time. As new features were needed, command line option switches were added to let the user use them, while maintaining backward compatibility for those who didn't. Backward compatibility is always a concern in system design, but is particularly important in the case of the tool chain (compilers, linker, and related tools), since it is a basic building block for the entire system. Over the years, applications have grown in size and complexity. Important concepts like dynamic linking that didn't exist in the original Unix system were invented. Object file formats changed. In the case of System V Release 4 Unix derivatives like Solaris, the ELF (Extensible Linking Format) was adopted. Since then, the ELF system has evolved to provide tools needed to manage today's larger and more complex environments. Features such as lazy loading, and direct bindings have been added. In an ideal world, many of these options would be defaults, with rarely used options that allow the user to turn them off. However, the reality is exactly the reverse: For backward compatibility, these features are all options that must be explicitly turned on by the user. This has led to a situation in which most applications do not take advantage of the many improvements that have been made in linking over the last 20 years. If their code seems to link and run without issue, what motivation does a developer have to read a complex manpage, absorb the information provided, choose the features that matter for their application, and apply them? Experience shows that only the most motivated and diligent programmers will make that effort. We know that most programs would be improved if we could just get you to use the various whizzy features that we provide, but the defaults conspire against us. We have long wanted to do something to make it easier for our users to use the linkers more effectively. There have been many conversations over the years regarding this issue, and how to address it. They always break down along the following lines: Change ld Defaults Since the world would be a better place the newer ld features were the defaults, why not change things to make it so? This idea is simple, elegant, and impossible. Doing so would break a large number of existing applications, including those of ISVs, big customers, and a plethora of existing open source packages. In each case, the owner of that code may choose to follow our lead and fix their code, or they may view it as an invitation to reconsider their commitment to our platform. Backward compatibility, and our installed base of working software, is one of our greatest assets, and not something to be lightly put at risk. Breaking backward compatibility at this level of the system is likely to do more harm than good. But, it sure is tempting. New Link-Editor One might create a new linker command, not called 'ld', leaving the old command as it is. The new one could use the same code as ld, but would offer only modern options, with the proper defaults for features such as direct binding. The resulting link-editor would be a pleasure to use. However, the approach is doomed to niche status. There is a vast pile of exiting code in the world built around the existing ld command, that reaches back to the 1970's. ld use is embedded in large and unknown numbers of makefiles, and is used by name by compilers that execute it. A Unix link-editor that is not named ld will not find a majority audience no matter how good it might be. Finally, a new linker command will eventually cease to be new, and will accumulate its own burden of backward compatibility issues. An Option To Make ld Do The Right Things Automatically This line of reasoning is best summarized by a CR filed in 2005, entitled 6239804 make it easier for ld(1) to do what's best The idea is to have a '-z best' option that unchains ld from its backward compatibility commitment, and allows it to turn on the "best" set of features, as determined by the authors of ld. The specific set of features enabled by -z best would be subject to change over time, as requirements change. This idea is more realistic than the other two, but was never implemented because it has some important issues that we could never answer to our satisfaction: The -z best proposal assumes that the user can turn it on, and trust it to select good options without the user needing to be aware of the options being applied. This is a fallacy. Features such as direct bindings require the user to do some analysis to ensure that the resulting program will still operate properly. A user who is willing to do the work to verify that what -z best does will be OK for their application is capable of turning on those features directly, and therefore gains little added benefit from -z best. The intent is that when a user opts into -z best, that they understand that z best is subject to sometimes incompatible evolution. Experience teaches us that this won't work. People will use this feature, the meaning of -z best will change, code that used to build will fail, and then there will be complaints and demands to retract the change. When (not if) this occurs, we will of course defend our actions, and point at the disclaimer. We'll win some of those debates, and lose others. Ultimately, we'll end up with -z best2 (-z better), or other compromises, and our goal of simplifying the world will have failed. The -z best idea rolls up a set of features that may or may not be related to each other into a unit that must be taken wholesale, or not at all. It could be that only a subset of what it does is compatible with a given application, in which case the user is expected to abandon -z best and instead set the options that apply to their application directly. In doing so, they lose one of the benefits of -z best, that if you use it, future versions of ld may choose a different set of options, and automatically improve the object through the act of rebuilding it. I drew two conclusions from the above history: For a link-editor, backward compatibility is vital. If a given command line linked your application 10 years ago, you have every reason to expect that it will link today, assuming that the libraries you're linking against are still available and compatible with their previous interfaces. For an application of any size or complexity, there is no substitute for the work involved in examining the code and determining which linker options apply and which do not. These options are largely orthogonal to each other, and it can be reasonable not to use any or all of them, depending on the situation, even in modern applications. It is a mistake to tie them together. The idea for -z guidance came from consideration of these points. By decoupling the advice from the act of taking the advice, we can retain the good aspects of -z best while avoiding its pitfalls: -z guidance gives advice, but the decision to take that advice remains with the user who must evaluate its merit and make a decision to take it or not. As such, we are free to change the specific guidance given in future releases of ld, without breaking existing applications. The only fallout from this will be some new warnings in the build output, which can be ignored or dealt with at the user's convenience. It does not couple the various features given into a single "take it or leave it" option, meaning that there will never be a need to offer "-zguidance2", or other such variants as things change over time. Guidance has the potential to be our final word on this subject. The user is given the flexibility to disable specific categories of guidance without losing the benefit of others, including those that might be added to future versions of the system. Although -z fatal-warnings stands on its own as a useful feature, it is of particular interest in combination with -z guidance. Used together, the guidance turns from advice to hard requirement: The user must either make the suggested change, or explicitly reject the advice by specifying a guidance exception token, in order to get a build. This is valuable in environments with high coding standards. ld Command Line Options The guidance effort resulted in new link-editor options for guidance and for turning warnings into fatal errors. Before I reproduce that text here, I'd like to highlight the strategic decisions embedded in the guidance feature: In order to get guidance, you have to opt in. We hope you will opt in, and believe you'll get better objects if you do, but our default mode of operation will continue as it always has, with full backward compatibility, and without judgement. Guidance suggestions always offers specific advice, and not vague generalizations. You can disable some guidance without turning off the entire feature. When you get guidance warnings, you can choose to take the advice, or you can specify a keyword to disable guidance for just that category. This allows you to get guidance for things that are useful to you, without being bothered about things that you've already considered and dismissed. As the world changes, we will add new guidance to steer you in the right direction. All such new guidance will come with a keyword that let's you turn it off. In order to facilitate building your code on different versions of Solaris, we quietly ignore any guidance keywords we don't recognize, assuming that they are intended for newer versions of the link-editor. If you want to see what guidance tokens ld does and does not recognize on your system, you can use the ld debugging feature as follows: % ld -Dargs -z guidance=foo,nodefs debug: debug: Solaris Linkers: 5.11-1.2275 debug: debug: arg[1] option=-D: option-argument: args debug: arg[2] option=-z: option-argument: guidance=foo,nodefs debug: warning: unrecognized -z guidance item: foo The -z fatal-warning option is straightforward, and generally useful in environments with strict coding standards. Note that the GNU ld already had this feature, and we accept their option names as synonyms: -z fatal-warnings | nofatal-warnings --fatal-warnings | --no-fatal-warnings The -z fatal-warnings and the --fatal-warnings option cause the link-editor to treat warnings as fatal errors. The -z nofatal-warnings and the --no-fatal-warnings option cause the link-editor to treat warnings as non-fatal. This is the default behavior. The -z guidance option is defined as follows: -z guidance[=item1,item2,...] Provide guidance messages to suggest ld options that can improve the quality of the resulting object, or which are otherwise considered to be beneficial. The specific guidance offered is subject to change over time as the system evolves. Obsolete guidance offered by older versions of ld may be dropped in new versions. Similarly, new guidance may be added to new versions of ld. Guidance therefore always represents current best practices. It is possible to enable guidance, while preventing specific guidance messages, by providing a list of item tokens, representing the class of guidance to be suppressed. In this way, unwanted advice can be suppressed without losing the benefit of other guidance. Unrecognized item tokens are quietly ignored by ld, allowing a given ld command line to be executed on a variety of older or newer versions of Solaris. The guidance offered by the current version of ld, and the item tokens used to disable these messages, are as follows. Specify Required Dependencies Dynamic executables and shared objects should explicitly define all of the dependencies they require. Guidance recommends the use of the -z defs option, should any symbol references remain unsatisfied when building dynamic objects. This guidance can be disabled with -z guidance=nodefs. Do Not Specify Non-Required Dependencies Dynamic executables and shared objects should not define any dependencies that do not satisfy the symbol references made by the dynamic object. Guidance recommends that unused dependencies be removed. This guidance can be disabled with -z guidance=nounused. Lazy Loading Dependencies should be identified for lazy loading. Guidance recommends the use of the -z lazyload option should any dependency be processed before either a -z lazyload or -z nolazyload option is encountered. This guidance can be disabled with -z guidance=nolazyload. Direct Bindings Dependencies should be referenced with direct bindings. Guidance recommends the use of the -B direct, or -z direct options should any dependency be processed before either of these options, or the -z nodirect option is encountered. This guidance can be disabled with -z guidance=nodirect. Pure Text Segment Dynamic objects should not contain relocations to non-writable, allocable sections. Guidance recommends compiling objects with Position Independent Code (PIC) should any relocations against the text segment remain, and neither the -z textwarn or -z textoff options are encountered. This guidance can be disabled with -z guidance=notext. Mapfile Syntax All mapfiles should use the version 2 mapfile syntax. Guidance recommends the use of the version 2 syntax should any mapfiles be encountered that use the version 1 syntax. This guidance can be disabled with -z guidance=nomapfile. Library Search Path Inappropriate dependencies that are encountered by ld are quietly ignored. For example, a 32-bit dependency that is encountered when generating a 64-bit object is ignored. These dependencies can result from incorrect search path settings, such as supplying an incorrect -L option. Although benign, this dependency processing is wasteful, and might hide a build problem that should be solved. Guidance recommends the removal of any inappropriate dependencies. This guidance can be disabled with -z guidance=nolibpath. In addition, -z guidance=noall can be used to entirely disable the guidance feature. See Chapter 7, Link-Editor Quick Reference, in the Linker and Libraries Guide for more information on guidance and advice for building better objects. Example The following example demonstrates how the guidance feature is intended to work. We will build a shared object that has a variety of shortcomings: Does not specify all it's dependencies Specifies dependencies it does not use Does not use direct bindings Uses a version 1 mapfile Contains relocations to the readonly allocable text (not PIC) This scenario is sadly very common — many shared objects have one or more of these issues. % cat hello.c #include <stdio.h> #include <unistd.h> void hello(void) { printf("hello user %d\n", getpid()); } % cat mapfile.v1 # This version 1 mapfile will trigger a guidance message % cc hello.c -o hello.so -G -M mapfile.v1 -lelf As you can see, the operation completes without error, resulting in a usable object. However, turning on guidance reveals a number of things that could be better: % cc hello.c -o hello.so -G -M mapfile.v1 -lelf -zguidance ld: guidance: version 2 mapfile syntax recommended: mapfile.v1 ld: guidance: -z lazyload option recommended before first dependency ld: guidance: -B direct or -z direct option recommended before first dependency Undefined first referenced symbol in file getpid hello.o (symbol belongs to implicit dependency /lib/libc.so.1) printf hello.o (symbol belongs to implicit dependency /lib/libc.so.1) ld: warning: symbol referencing errors ld: guidance: -z defs option recommended for shared objects ld: guidance: removal of unused dependency recommended: libelf.so.1 warning: Text relocation remains referenced against symbol offset in file .rodata1 (section) 0xa hello.o getpid 0x4 hello.o printf 0xf hello.o ld: guidance: position independent (PIC) code recommended for shared objects ld: guidance: see ld(1) -z guidance for more information Given the explicit advice in the above guidance messages, it is relatively easy to modify the example to do the right things: % cat mapfile.v2 # This version 2 mapfile will not trigger a guidance message $mapfile_version 2 % cc hello.c -o hello.so -Kpic -G -Bdirect -M mapfile.v2 -lc -zguidance There are situations in which the guidance does not fit the object being built. For instance, you want to build an object without direct bindings: % cc -Kpic hello.c -o hello.so -G -M mapfile.v2 -lc -zguidance ld: guidance: -B direct or -z direct option recommended before first dependency ld: guidance: see ld(1) -z guidance for more information It is easy to disable that specific guidance warning without losing the overall benefit from allowing the remainder of the guidance feature to operate: % cc -Kpic hello.c -o hello.so -G -M mapfile.v2 -lc -zguidance=nodirect Conclusions The linking guidelines enforced by the ld guidance feature correspond rather directly to our standards for building the core Solaris OS. I'm sure that comes as no surprise. It only makes sense that we would want to build our own product as well as we know how. Solaris is usually the first significant test for any new linker feature. We now enable guidance by default for all builds, and the effect has been very positive. Guidance helps us find suboptimal objects more quickly. Programmers get concrete advice for what to change instead of vague generalities. Even in the cases where we override the guidance, the makefile rules to do so serve as documentation of the fact. Deciding to use guidance is likely to cause some up front work for most code, as it forces you to consider using new features such as direct bindings. Such investigation is worthwhile, but does not come for free. However, the guidance suggestions offer a structured and straightforward way to tackle modernizing your objects, and once that work is done, for keeping them that way. The investment is often worth it, and will replay you in terms of better performance and fewer problems. I hope that you find guidance to be as useful as we have.

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  • Sorting and Filtering By Model-Based LOV Display Value

    - by Steven Davelaar
    If you use a model-based LOV and you use display type "choice", then ADF nicely displays the display value, even if the table is read-only. In the screen shot below, you see the RegionName attribute displayed instead of the RegionId. This is accomplished by the model-based LOV, I did not modify the Countries view object to include a join with Regions.  Also note the sort icon, the table is sorted by RegionId. This sorting typically results in a bug reported by your test team. Europe really shouldn't come before America when sorting ascending, right? To fix this, we could of course change the Countries view object query and add a join with the Regions table to include the RegionName attribute. If the table is updateable, we still need the choice list, so we need to move the model-based LOV from the RegionId attribute to the RegionName attribute and hide the RegionId attribute in the table. But that is a lot of work for such a simple requirement, in particular if we have lots of model-based choice lists in our view object. Fortunately, there is an easier way to do this, with some generic code in your view object base class that fixes this at once for all model-based choice lists that we have defined in our application. The trick is to override the method getSortCriteria() in the base view object class. By default, this method returns null because the sorting is done in the database through a SQL Order By clause. However, if the getSortCriteria method does return a sort criteria the framework will perform in memory sorting which is what we need to achieve sorting by region name. So, inside this method we need to evaluate the Order By clause, and if the order by column matches an attribute that has a model-based LOV choicelist defined with a display attribute that is different from the value attribute, we need to return a sort criterria. Here is the complete code of this method: public SortCriteria[] getSortCriteria() {   String orderBy = getOrderByClause();          if (orderBy!=null )   {     boolean descending = false;     if (orderBy.endsWith(" DESC"))      {       descending = true;       orderBy = orderBy.substring(0,orderBy.length()-5);     }     // extract column name, is part after the dot     int dotpos = orderBy.lastIndexOf(".");     String columnName = orderBy.substring(dotpos+1);     // loop over attributes and find matching attribute     AttributeDef orderByAttrDef = null;     for (AttributeDef attrDef : getAttributeDefs())     {       if (columnName.equals(attrDef.getColumnName()))       {         orderByAttrDef = attrDef;         break;       }     }     if (orderByAttrDef!=null && "choice".equals(orderByAttrDef.getProperty("CONTROLTYPE"))          && orderByAttrDef.getListBindingDef()!=null)     {       String orderbyAttr = orderByAttrDef.getName();       String[] displayAttrs = orderByAttrDef.getListBindingDef().getListDisplayAttrNames();       String[] listAttrs = orderByAttrDef.getListBindingDef().getListAttrNames();       // if first list display attributes is not the same as first list attribute, than the value       // displayed is different from the value copied back to the order by attribute, in which case we need to       // use our custom comparator       if (displayAttrs!=null && listAttrs!=null && displayAttrs.length>0 && !displayAttrs[0].equals(listAttrs[0]))       {                  SortCriteriaImpl sc1 = new SortCriteriaImpl(orderbyAttr, descending);         SortCriteria[] sc = new SortCriteriaImpl[]{sc1};         return sc;                           }     }     }   return super.getSortCriteria(); } If this method returns a sort criteria, then the framework will call the sort method on the view object. The sort method uses a Comparator object to determine the sequence in which the rows should be returned. This comparator is retrieved by calling the getRowComparator method on the view object. So, to ensure sorting by our display value, we need to override this method to return our custom comparator: public Comparator getRowComparator() {   return new LovDisplayAttributeRowComparator(getSortCriteria()); } The custom comparator class extends the default RowComparator class and overrides the method compareRows and looks up the choice display value to compare the two rows. The complete code of this class is included in the sample application.  With this code in place, clicking on the Region sort icon nicely sorts the countries by RegionName, as you can see below. When using the Query-By-Example table filter at the top of the table, you typically want to use the same choice list to filter the rows. One way to do that is documented in ADF code corner sample 16 - How To Customize the ADF Faces Table Filter.The solution in this sample is perfectly fine to use. This sample requires you to define a separate iterator binding and associated tree binding to populate the choice list in the table filter area using the af:iterator tag. You might be able to reuse the same LOV view object instance in this iterator binding that is used as view accessor for the model-bassed LOV. However, I have seen quite a few customers who have a generic LOV view object (mapped to one "refcodes" table) with the bind variable values set in the LOV view accessor. In such a scenario, some duplicate work is needed to get a dedicated view object instance with the correct bind variables that can be used in the iterator binding. Looking for ways to maximize reuse, wouldn't it be nice if we could just reuse our model-based LOV to populate this filter choice list? Well we can. Here are the basic steps: 1. Create an attribute list binding in the page definition that we can use to retrieve the list of SelectItems needed to populate the choice list <list StaticList="false" Uses="LOV_RegionId"               IterBinding="CountriesView1Iterator" id="RegionId"/>  We need this "current row" list binding because the implicit list binding used by the item in the table is not accessible outside a table row, we cannot use the expression #{row.bindings.RegionId} in the table filter facet. 2. Create a Map-style managed bean with the get method retrieving the list binding as key, and returning the list of SelectItems. To return this list, we take the list of selectItems contained by the list binding and replace the index number that is normally used as key value with the actual attribute value that is set by the choice list. Here is the code of the get method:  public Object get(Object key) {   if (key instanceof FacesCtrlListBinding)   {     // we need to cast to internal class FacesCtrlListBinding rather than JUCtrlListBinding to     // be able to call getItems method. To prevent this import, we could evaluate an EL expression     // to get the list of items     FacesCtrlListBinding lb = (FacesCtrlListBinding) key;     if (cachedFilterLists.containsKey(lb.getName()))     {       return cachedFilterLists.get(lb.getName());     }     List<SelectItem> items = (List<SelectItem>)lb.getItems();     if (items==null || items.size()==0)     {       return items;     }     List<SelectItem> newItems = new ArrayList<SelectItem>();     JUCtrlValueDef def = ((JUCtrlValueDef)lb.getDef());     String valueAttr = def.getFirstAttrName();     // the items list has an index number as value, we need to replace this with the actual     // value of the attribute that is copied back by the choice list     for (int i = 0; i < items.size(); i++)     {       SelectItem si = (SelectItem) items.get(i);       Object value = lb.getValueFromList(i);       if (value instanceof Row)       {         Row row = (Row) value;         si.setValue(row.getAttribute(valueAttr));                 }       else       {         // this is the "empty" row, set value to empty string so all rows will be returned         // as user no longer wants to filter on this attribute         si.setValue("");       }       newItems.add(si);     }     cachedFilterLists.put(lb.getName(), newItems);     return newItems;   }   return null; } Note that we added caching to speed up performance, and to handle the situation where table filters or search criteria are set such that no rows are retrieved in the table. When there are no rows, there is no current row and the getItems method on the list binding will return no items.  An alternative approach to create the list of SelectItems would be to retrieve the iterator binding from the list binding and loop over the rows in the iterator binding rowset. Then we wouldn't need the import of the ADF internal oracle.adfinternal.view.faces.model.binding.FacesCtrlListBinding class, but then we need to figure out the display attributes from the list binding definition, and possible separate them with a dash if multiple display attributes are defined in the LOV. Doable but less reuse and more work. 3. Inside the filter facet for the column create an af:selectOneChoice with the value property of the f:selectItems tag referencing the get method of the managed bean:  <f:facet name="filter">   <af:selectOneChoice id="soc0" autoSubmit="true"                       value="#{vs.filterCriteria.RegionId}">     <!-- attention: the RegionId list binding must be created manually in the page definition! -->                       <f:selectItems id="si0"                    value="#{viewScope.TableFilterChoiceList[bindings.RegionId]}"/>   </af:selectOneChoice> </f:facet> Note that the managed bean is defined in viewScope for the caching to take effect. Here is a screen shot of the tabe filter in action: You can download the sample application here. 

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  • Mouse Clicks, Reactive Extensions and StreamInsight Mashup

    I had an hour spare this afternoon so I wanted to have another play with Reactive Extensions in .Net and StreamInsight.  I also didn’t want to simply use a console window as a way of gathering events so I decided to use a windows form instead. The task I set myself was this. Whenever I click on my form I want to subscribe to the event and output its location to the console window and also the timestamp of the event.  In addition to this I want to know for every mouse click I do, how many mouse clicks have happened in the last 5 seconds. The second point here is really interesting.  I have often found this when working with people on problems.  It is how you ask the question that determines how you tackle the problem.  I will show 2 ways of possibly answering the second question depending on how the question was interpreted. As a side effect of this example I will show how time in StreamInsight can stand still.  This is an important concept and we can see it in the output later. Now to the code.  I will break it all down in this blogpost but you can download the solution and see it all together. I created a Console application and then instantiate a windows form.   frm = new Form(); Thread g = new Thread(CallUI); g.SetApartmentState(ApartmentState.STA); g.Start();   Call UI looks like this   static void CallUI() { System.Windows.Forms.Application.Run(frm); frm.Activate(); frm.BringToFront(); }   Now what we need to do is create an observable from the MouseClick event on the form.  For this we use the Reactive Extensions.   var lblevt = Observable.FromEvent<MouseEventArgs>(frm, "MouseClick").Timestamp();   As mentioned earlier I have two objectives in this example and to solve the first I am going to again use the Reactive extensions.  Let’s subscribe to the MouseClick event and output the location and timestamp to the console. lblevt.Subscribe(evt => { Console.WriteLine("Clicked: {0}, {1} ", evt.Value.EventArgs.Location,evt.Timestamp); }); That should take care of obective #1 but what about the second objective.  For that we need some temporal windowing and this means StreamInsight.  First we need to turn our Observable collection of MouseClick events into a PointStream Server s = Server.Create("Default"); Microsoft.ComplexEventProcessing.Application a = s.CreateApplication("MouseClicks"); var input = lblevt.ToPointStream( a, evt => PointEvent.CreateInsert( evt.Timestamp, new { loc = evt.Value.EventArgs.Location.ToString(), ts = evt.Timestamp.ToLocalTime().ToString() }), AdvanceTimeSettings.IncreasingStartTime);   Now that we have created out PointStream we need to do something with it and this is where we get to our second objective.  It is pretty clear that we want some kind of windowing but what? Here is one way of doing it.  It might not be what you wanted but again it is how the second objective is interpreted   var q = from i in input.TumblingWindow(TimeSpan.FromSeconds(5), HoppingWindowOutputPolicy.ClipToWindowEnd) select new { CountOfClicks = i.Count() };   The above code creates tumbling windows of 5 seconds and counts the number of events in the windows.  If there are no events in the window then no result is output.  Likewise until an event (MouseClick) is issued then we do not see anything in the output (that is not strictly true because it is the CTI strapped to our MouseClick events that flush the events through the StreamInsight engine not the events themselves).  This approach is centred around the windows and not the events.  Until the windows complete and a CTI is issued then no events are pushed through. An alternate way of answering our second question is below   var q = from i in input.AlterEventDuration(evt => TimeSpan.FromSeconds(5)).SnapshotWindow(SnapshotWindowOutputPolicy.Clip) select new { CountOfClicks = i.Count() };   In this code we extend the duration of each MouseClick to five seconds.  We then create  Snapshot Windows over those events.  Snapshot windows are discussed in detail here.  With this solution we are centred around the events.  It is the events that are driving the output.  Let’s have a look at the output from this solution as it may be a little confusing. First though let me show how we get the output from StreamInsight into the Console window. foreach (var x in q.ToPointEnumerable().Where(e => e.EventKind != EventKind.Cti)) { Console.WriteLine(x.Payload.CountOfClicks); }   Ok so now to the output.   The table at the top shows the output from our routine and the table at the bottom helps to explain the output.  One of the things that will help as well is, you will note that for our PointStream we set the issuing of CTIs to be IncreasingStartTime.  What this means is that the CTI is placed right at the start of the event so will not flush the event with which it was issued but will flush those prior to it.  In the bottom table the Blue fill is where we issued a click.  Yellow fill is the duration and boundaries of our events.  The numbers at the bottom indicate the count of events   Clicked 22:40:16                                 Clicked 23:40:18                                 1                                   Clicked 23:40:20                                 2                                   Clicked 23:40:22                                 3                                   2                                   Clicked 23:40:24                                 3                                   2                                   Clicked 23:40:32                                 3                                   2                                   1                                                                                                         secs 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32                                                                                                                                                                                                                         counts   1   2 3 2 3 2 3   2   1           What we can see here in the output is that the counts include all the end edges that have occurred between the mouse clicks.  If we look specifically at the mouse click at 22:40:32. then we see that 3 events are returned to us. These include the following End Edge count at 22:40:25 End Edge count at 22:40:27 End Edge count at 22:40:29 Another thing we notice is that until we actually issue a CTI at 22:40:32 then those last 3 snapshot window counts will never be reported. Hopefully this has helped to explain  a few concepts around StreamInsight and the IObservable() pattern.   You can download this solution from here and play.  You will need the Reactive Framework from here and StreamInsight 1.1

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