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  • In a given Json, search for the particular given string based on key, return true if found, else false Using jQuery/Javascript

    - by NaanuManu
    Given JSON String/object {"selectAll":false,"include":{"country_197":{"id":"197","data_type":"country","name":"Singapore","desc":"","parent_key_id":"all_all","status":""},"country_100":{"id":"100","data_type":"country","name":"India","desc":"","parent_key_id":"all_all","status":""}},"exclude":{"state_2":{"id":"2","data_type":"state","name":"Andhra Pradesh","desc":"","parent_key_id":"country_100","status":""}}} Given search string is: country_100 Required : Have to search for country_100 in Given JSON String/object by key parent_key_id Ex: searching country_100 is found : {"selectAll":false,"include":{"country_197":{"id":"197","data_type":"country","name":"Singapore","desc":"","parent_key_id":"all_all","status":""},"country_100":{"id":"100","data_type":"country","name":"India","desc":"","parent_key_id":"all_all","status":""}},"exclude":{"state_2":{"id":"2","data_type":"state","name":"Andhra Pradesh","desc":"","parent_key_id":"**country_100**","status":""}}} So return True, else return false please help me in finding a solution.

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  • MYSQL Insert: How to save Query in the database only one time - duplicate key doesn't work!

    - by elmaso
    hello, I want to save a query only one time in the database, this is my code: $querystat = mysql_real_escape_string($_GET['q']); $datetime = time(); if( ($querystat != $_SESSION['prev_search']) OR ( ($datetime - $_SESSION['datetime']) > 60) ) { $insertquery = "INSERT INTO `query` ( `searchquery` , `datetime`) VALUES ( '$querystat' , '$datetime') ON DUPLICATE KEY UPDATE searchquery='$querystat';"; mysql_query($insertquery, $db); } maybe something with == 0 ?

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  • INSERT ... ON DUPLICATE KEY UPDATE with WHERE?

    - by Raven
    Hi! I'm doing a INSERT ... ON DUPLICATE KEY UPDATE but I need the update part to be conditional, only doing the update if some extra condition has changed. However, WHERE is not allowed on this UPDATE. Is there any workaround for this? I can't do combinations of INSERT/UPDATE/SELECT since this needs to work over a replication.

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  • Openvpn plugin openvpn-auth-ldap does not bind to Active Directory

    - by Selivanov Pavel
    I'm trying to configure OpenVPN with openvpn-auth-ldap plugin to authorize users via Active Directory LDAP. When I use the same server config without plugin option, and add client config with generated client key and cert, connection is successful, so problem is in the plugin. server.conf: plugin /usr/lib/openvpn/openvpn-auth-ldap.so "/etc/openvpn-test/openvpn-auth-ldap.conf" port 1194 proto tcp dev tun keepalive 10 60 topology subnet server 10.0.2.0 255.255.255.0 tls-server ca ca.crt dh dh1024.pem cert server.crt key server.key #crl-verify crl.pem persist-key persist-tun user nobody group nogroup verb 3 mute 20 openvpn-auth-ldap.conf: <LDAP> URL ldap://dc1.domain:389 TLSEnable no BindDN cn=bot_auth,cn=Users,dc=domain Password bot_auth Timeout 15 FollowReferrals yes </LDAP> <Authorization> BaseDN "cn=Users,dc=domain" SearchFilter "(sAMAccountName=%u)" RequireGroup false # <Group> # BaseDN "ou=groups,dc=mycompany,dc=local" # SearchFilter "(|(cn=developers)(cn=artists))" # MemberAttribute uniqueMember # </Group> </Authorization> Top-level domain in AD is used by historical reasons. Analogue configuration is working for Apache 2.2 in mod-authzn-ldap. User and password are correct. client.conf: remote server_name port 1194 proto tcp client pull remote-cert-tls server dev tun resolv-retry infinite nobind ca ca.crt ; with keys - works fine #cert test.crt #key test.key ; without keys - by password auth-user-pass persist-tun verb 3 mute 20 In server log there is string PLUGIN_INIT: POST /usr/lib/openvpn/openvpn-auth-ldap.so '[/usr/lib/openvpn/openvpn-auth-ldap.so] [/etc/openvpn-test/openvpn-auth-ldap.conf]' which indicates, that plugin failed. I can telnet to dc1.domain:389, so this is not network/firewall problem. Later server says TLS Error: TLS object -> incoming plaintext read error TLS handshake failed - without plugin it tryes to do usal key authentification. server log: Tue Nov 22 03:06:20 2011 OpenVPN 2.1.3 i486-pc-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [MH] [PF_INET6] [eurephia] built on Oct 21 2010 Tue Nov 22 03:06:20 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables Tue Nov 22 03:06:20 2011 PLUGIN_INIT: POST /usr/lib/openvpn/openvpn-auth-ldap.so '[/usr/lib/openvpn/openvpn-auth-ldap.so] [/etc/openvpn-test/openvpn-auth-ldap.conf]' intercepted=PLUGIN_AUTH_USER_PASS_VERIFY|PLUGIN_CLIENT_CONNECT|PLUGIN_CLIENT_DISCONNECT Tue Nov 22 03:06:20 2011 Diffie-Hellman initialized with 1024 bit key Tue Nov 22 03:06:20 2011 /usr/bin/openssl-vulnkey -q -b 1024 -m <modulus omitted> Tue Nov 22 03:06:20 2011 Control Channel Authentication: using 'ta.key' as a OpenVPN static key file Tue Nov 22 03:06:20 2011 Outgoing Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication Tue Nov 22 03:06:20 2011 Incoming Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication Tue Nov 22 03:06:20 2011 TLS-Auth MTU parms [ L:1543 D:168 EF:68 EB:0 ET:0 EL:0 ] Tue Nov 22 03:06:20 2011 Socket Buffers: R=[87380->131072] S=[16384->131072] Tue Nov 22 03:06:20 2011 TUN/TAP device tun1 opened Tue Nov 22 03:06:20 2011 TUN/TAP TX queue length set to 100 Tue Nov 22 03:06:20 2011 /sbin/ifconfig tun1 10.0.2.1 netmask 255.255.255.0 mtu 1500 broadcast 10.0.2.255 Tue Nov 22 03:06:20 2011 Data Channel MTU parms [ L:1543 D:1450 EF:43 EB:4 ET:0 EL:0 ] Tue Nov 22 03:06:20 2011 GID set to nogroup Tue Nov 22 03:06:20 2011 UID set to nobody Tue Nov 22 03:06:20 2011 Listening for incoming TCP connection on [undef] Tue Nov 22 03:06:20 2011 TCPv4_SERVER link local (bound): [undef] Tue Nov 22 03:06:20 2011 TCPv4_SERVER link remote: [undef] Tue Nov 22 03:06:20 2011 MULTI: multi_init called, r=256 v=256 Tue Nov 22 03:06:20 2011 IFCONFIG POOL: base=10.0.2.2 size=252 Tue Nov 22 03:06:20 2011 MULTI: TCP INIT maxclients=1024 maxevents=1028 Tue Nov 22 03:06:20 2011 Initialization Sequence Completed Tue Nov 22 03:07:10 2011 MULTI: multi_create_instance called Tue Nov 22 03:07:10 2011 Re-using SSL/TLS context Tue Nov 22 03:07:10 2011 Control Channel MTU parms [ L:1543 D:168 EF:68 EB:0 ET:0 EL:0 ] Tue Nov 22 03:07:10 2011 Data Channel MTU parms [ L:1543 D:1450 EF:43 EB:4 ET:0 EL:0 ] Tue Nov 22 03:07:10 2011 Local Options hash (VER=V4): 'c413e92e' Tue Nov 22 03:07:10 2011 Expected Remote Options hash (VER=V4): 'd8421bb0' Tue Nov 22 03:07:10 2011 TCP connection established with [AF_INET]10.0.0.9:47808 Tue Nov 22 03:07:10 2011 TCPv4_SERVER link local: [undef] Tue Nov 22 03:07:10 2011 TCPv4_SERVER link remote: [AF_INET]10.0.0.9:47808 Tue Nov 22 03:07:11 2011 10.0.0.9:47808 TLS: Initial packet from [AF_INET]10.0.0.9:47808, sid=a2cd4052 84b47108 Tue Nov 22 03:07:11 2011 10.0.0.9:47808 TLS_ERROR: BIO read tls_read_plaintext error: error:140890C7:SSL routines:SSL3_GET_CLIENT_CERTIFICATE:peer did not return a certificate Tue Nov 22 03:07:11 2011 10.0.0.9:47808 TLS Error: TLS object -> incoming plaintext read error Tue Nov 22 03:07:11 2011 10.0.0.9:47808 TLS Error: TLS handshake failed Tue Nov 22 03:07:11 2011 10.0.0.9:47808 Fatal TLS error (check_tls_errors_co), restarting Tue Nov 22 03:07:11 2011 10.0.0.9:47808 SIGUSR1[soft,tls-error] received, client-instance restarting Tue Nov 22 03:07:11 2011 TCP/UDP: Closing socket client log: Tue Nov 22 03:06:18 2011 OpenVPN 2.1.3 x86_64-pc-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [MH] [PF_INET6] [eurephia] built on Oct 22 2010 Enter Auth Username:user Enter Auth Password: Tue Nov 22 03:06:25 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables Tue Nov 22 03:06:25 2011 Control Channel Authentication: using 'ta.key' as a OpenVPN static key file Tue Nov 22 03:06:25 2011 Outgoing Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication Tue Nov 22 03:06:25 2011 Incoming Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication Tue Nov 22 03:06:25 2011 Control Channel MTU parms [ L:1543 D:168 EF:68 EB:0 ET:0 EL:0 ] Tue Nov 22 03:06:25 2011 Socket Buffers: R=[87380->131072] S=[16384->131072] Tue Nov 22 03:06:25 2011 Data Channel MTU parms [ L:1543 D:1450 EF:43 EB:4 ET:0 EL:0 ] Tue Nov 22 03:06:25 2011 Local Options hash (VER=V4): 'd8421bb0' Tue Nov 22 03:06:25 2011 Expected Remote Options hash (VER=V4): 'c413e92e' Tue Nov 22 03:06:25 2011 Attempting to establish TCP connection with [AF_INET]10.0.0.2:1194 [nonblock] Tue Nov 22 03:06:26 2011 TCP connection established with [AF_INET]10.0.0.2:1194 Tue Nov 22 03:06:26 2011 TCPv4_CLIENT link local: [undef] Tue Nov 22 03:06:26 2011 TCPv4_CLIENT link remote: [AF_INET]10.0.0.2:1194 Tue Nov 22 03:06:26 2011 TLS: Initial packet from [AF_INET]10.0.0.2:1194, sid=7a3c2a0f bd35bca7 Tue Nov 22 03:06:26 2011 WARNING: this configuration may cache passwords in memory -- use the auth-nocache option to prevent this Tue Nov 22 03:06:26 2011 VERIFY OK: depth=1, /C=US/ST=CA/L=SanFrancisco/O=Fort-Funston/CN=Fort-Funston_CA/[email protected] Tue Nov 22 03:06:26 2011 Validating certificate key usage Tue Nov 22 03:06:26 2011 ++ Certificate has key usage 00a0, expects 00a0 Tue Nov 22 03:06:26 2011 VERIFY KU OK Tue Nov 22 03:06:26 2011 Validating certificate extended key usage Tue Nov 22 03:06:26 2011 ++ Certificate has EKU (str) TLS Web Server Authentication, expects TLS Web Server Authentication Tue Nov 22 03:06:26 2011 VERIFY EKU OK Tue Nov 22 03:06:26 2011 VERIFY OK: depth=0, /C=US/ST=CA/L=SanFrancisco/O=Fort-Funston/CN=server/[email protected] Tue Nov 22 03:06:26 2011 Connection reset, restarting [0] Tue Nov 22 03:06:26 2011 TCP/UDP: Closing socket Tue Nov 22 03:06:26 2011 SIGUSR1[soft,connection-reset] received, process restarting Tue Nov 22 03:06:26 2011 Restart pause, 5 second(s) ^CTue Nov 22 03:06:27 2011 SIGINT[hard,init_instance] received, process exiting Does anybody know how to get openvpn-auth-ldap wirking?

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  • ssh refuses to authenticate keys

    - by MixturaDementiae
    So I am setting up a connection between my machine [fedora 17] and a virtual machine running in Virtual Box in which is running CentOS 5. I have installed openssh from the repositories on CentOS, and I have configured everything as it follows: Protocol 2 HostKey /etc/ssh/ssh_host_rsa_key HostKey /etc/ssh/ssh_host_dsa_key SyslogFacility AUTHPRIV PermitRootLogin yes RSAAuthentication yes PubkeyAuthentication yes AuthorizedKeysFile /home/pigreco/.ssh/authorized_keys PasswordAuthentication no ChallengeResponseAuthentication yes GSSAPIAuthentication yes GSSAPICleanupCredentials yes UsePAM yes AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE AcceptEnv XMODIFIERS X11Forwarding yes Subsystem sftp /usr/libexec/openssh/sftp-server this is the configuration file sshd_config on the server i.e. on the CentOS. Moreover I have created a public/private key pair as usual on the .ssh/ folder in my home directory in my OS, i.e. Fedora, and then I've copied with scp the id_rsa.pub to the server and then I have appended its content to the file .ssh/authorized_keys on the server machine. The error that I get is the following: OpenSSH_5.9p1, OpenSSL 1.0.0j-fips 10 May 2012 debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 50: Applying options for * debug1: Connecting to 192.168.100.13 [192.168.100.13] port 22. debug1: Connection established. debug1: identity file /home/mayhem/.ssh/identity type -1 debug1: identity file /home/mayhem/.ssh/identity-cert type -1 debug1: identity file /home/mayhem/.ssh/id_rsa type 1 debug1: identity file /home/mayhem/.ssh/id_rsa-cert type -1 debug1: identity file /home/mayhem/.ssh/id_dsa type -1 debug1: identity file /home/mayhem/.ssh/id_dsa-cert type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3 debug1: match: OpenSSH_5.3 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.9 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5 none debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Server host key: RSA 16:e5:72:d1:37:94:1b:5e:3d:3a:e5:da:6f:df:0c:08 debug1: Host '192.168.100.13' is known and matches the RSA host key. debug1: Found key in /home/mayhem/.ssh/known_hosts:1 debug1: ssh_rsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,keyboard-interactive debug1: Next authentication method: gssapi-keyex debug1: No valid Key exchange context debug1: Next authentication method: gssapi-with-mic debug1: Unspecified GSS failure. Minor code may provide more information Cannot determine realm for numeric host address debug1: Unspecified GSS failure. Minor code may provide more information Cannot determine realm for numeric host address debug1: Unspecified GSS failure. Minor code may provide more information debug1: Unspecified GSS failure. Minor code may provide more information Cannot determine realm for numeric host address debug1: Next authentication method: publickey debug1: Offering RSA public key: /home/mayhem/.ssh/id_rsa debug1: Server accepts key: pkalg ssh-rsa blen 279 Agent admitted failure to sign using the key. debug1: Trying private key: /home/mayhem/.ssh/identity debug1: Trying private key: /home/mayhem/.ssh/id_dsa debug1: Next authentication method: keyboard-interactive Do you have some good suggestion of what I can do? thank you

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  • Is there any way to get the combine two xml into one xml in Linux.

    - by user28167
    XML one is something like that: <dict> <key>2</key> <array> <string>A</string> <string>B</string> </array> <key>3</key> <array> <string>C</string> <string>D</string> <string>E</string> </array> </dict> XML Two is something like that: <dict> <key>A</key> <array> <string>A1</string> <false/> <false/> <array> <string>Apple</string> <string>This is an apple</string> </array> <array> <string>Apple Pie</string> <string>I love Apple Pie.</string> </array> </array> <key>B</key> <array> <string>B7</string> <false/> <false/> <array> <string>Boy</string> <string>I am a boy.</string> </array> </array> </dict> I want to convert to this: <dict> <key>2</key> <array> <string>A, Apple, Apple Pie</string> <string>B, Boy</string> </array> ... </dict>

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  • UDISKS instead of HAL

    - by MeJ
    Does anybody have some expirence with udisks, because HAL won't be longer supported on the most linux distribution, so I am thinking of to use udisks for UDI in $(hal-find-by-property --key storage.bus --string usb) do HAL_TMP=`hal-get-property --udi $UDI --key storage.removable.media_available` if [ "$HAL_TMP" = "true" ]; then HAL_DEV=$(hal-get-property --udi $UDI --key block.device) HAL_SIZE=$(hal-get-property --udi $UDI --key storage.removable.media_size) HAL_TYPE=$(hal-get-property --udi $UDI --key storage.drive_type) How do I have to adapt the above mentioned commands but use udisks instead of hal Thanks!

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  • Two-Hop SSH connection with two separate public keys

    - by yigit
    We have the following ssh hop setup: localhost -> hub -> server hubuser@hub accepts the public key for localuser@localhost. serveruser@server accepts the public key for hubuser@hub. So we are issuing ssh -t hubuser@hub ssh serveruser@server for connecting to server. The problem with this setup is we can not scp directly to the server. I tried creating .ssh/config file like this: Host server user serveruser port 22 hostname server ProxyCommand ssh -q hubuser@hub 'nc %h %p' But I am not able to connect (yigit is localuser): $ ssh serveruser@server -v OpenSSH_6.1p1, OpenSSL 1.0.1c 10 May 2012 debug1: Reading configuration data /home/yigit/.ssh/config debug1: /home/yigit/.ssh/config line 19: Applying options for server debug1: Reading configuration data /etc/ssh/ssh_config debug1: Executing proxy command: exec ssh -q hubuser@hub 'nc server 22' debug1: permanently_drop_suid: 1000 debug1: identity file /home/yigit/.ssh/id_rsa type 1000 debug1: identity file /home/yigit/.ssh/id_rsa-cert type -1 debug1: identity file /home/yigit/.ssh/id_dsa type -1 debug1: identity file /home/yigit/.ssh/id_dsa-cert type -1 debug1: identity file /home/yigit/.ssh/id_ecdsa type -1 debug1: identity file /home/yigit/.ssh/id_ecdsa-cert type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9p1 Debian-5ubuntu1 debug1: match: OpenSSH_5.9p1 Debian-5ubuntu1 pat OpenSSH_5* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_6.1 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5 none debug1: kex: client->server aes128-ctr hmac-md5 none debug1: sending SSH2_MSG_KEX_ECDH_INIT debug1: expecting SSH2_MSG_KEX_ECDH_REPLY debug1: Server host key: ECDSA cb:ee:1f:78:82:1e:b4:39:c6:67:6f:4d:b4:01:f2:9f debug1: Host 'server' is known and matches the ECDSA host key. debug1: Found key in /home/yigit/.ssh/known_hosts:33 debug1: ssh_ecdsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey debug1: Next authentication method: publickey debug1: Offering RSA public key: /home/yigit/.ssh/id_rsa debug1: Authentications that can continue: publickey debug1: Trying private key: /home/yigit/.ssh/id_dsa debug1: Trying private key: /home/yigit/.ssh/id_ecdsa debug1: No more authentication methods to try. Permission denied (publickey). Notice that it is trying to use the public key localuser@localhost for authenticating on server and fails since it is not the right one. Is it possible to modify the ProxyCommand so that the key for hubuser@hub is used for authenticating on server?

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  • Lost all privileges since upgrading to 13.10

    - by Chris Poole
    Since upgrading to 13.10, I no longer have the 'privileges' to do the following things: Mount USB/CDROM drives Run software centre or software updater Press the GUI shut down or restart buttons Unlock my account in the 'settings - user accounts' section (padlock is greyed out) Also, when logging on as a guest user I get error messages relating to Compiz crashing with SIGSEGV and it hangs on a blank wallpaper screen. However, I still am able to use sudo in the terminal. Output of 'groups' is jenchris adm dialout cdrom sudo audio video plugdev lpadmin admin pulse pulse-access sambashare sudo usermod -U username doesn't have any effect Output of sudo dpkg-reconfigure -phigh -a acpid stop/waiting acpid start/running, process 30454 * Starting AppArmor profiles Skipping profile in /etc/apparmor.d/disable: usr.bin.firefox Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd [ OK ] * Reloading AppArmor profiles Skipping profile in /etc/apparmor.d/disable: usr.bin.firefox Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd [ OK ] apport stop/waiting apport start/running gpg: key 437D05B5: "Ubuntu Archive Automatic Signing Key <[email protected]>" not changed gpg: key FBB75451: "Ubuntu CD Image Automatic Signing Key <[email protected]>" not changed gpg: key C0B21F32: "Ubuntu Archive Automatic Signing Key (2012) <[email protected]>" not changed gpg: key EFE21092: "Ubuntu CD Image Automatic Signing Key (2012) <[email protected]>" not changed gpg: Total number processed: 4 gpg: unchanged: 4 atd stop/waiting atd start/running, process 1388 avahi-daemon stop/waiting avahi-daemon start/running, process 1521 Rebuilding /usr/share/applications/bamf-2.index... update-alternatives: using /usr/share/man/man7/bash-builtins.7.gz to provide /usr/share/man/man7/builtins.7.gz (builtins.7.gz) in auto mode update-binfmts: warning: current package is openjdk-7, but binary format already installed by openjdk-6 binfmt-support stop/waiting bluetooth stop/waiting bluetooth start/running, process 4255 update-initramfs: deferring update (trigger activated) /var/lib/dpkg/info/compiz.config: 1: /var/lib/dpkg/info/compiz.config: [general]: not found /var/lib/dpkg/info/compiz.config: 2: /var/lib/dpkg/info/compiz.config: backend: not found /var/lib/dpkg/info/compiz.config: 3: /var/lib/dpkg/info/compiz.config: plugin_list_autosort: not found /var/lib/dpkg/info/compiz.config: 5: /var/lib/dpkg/info/compiz.config: [gnome_session]: not found /var/lib/dpkg/info/compiz.config: 6: /var/lib/dpkg/info/compiz.config: backend: not found /var/lib/dpkg/info/compiz.config: 7: /var/lib/dpkg/info/compiz.config: integration: not found /var/lib/dpkg/info/compiz.config: 8: /var/lib/dpkg/info/compiz.config: plugin_list_autosort: not found /var/lib/dpkg/info/compiz.config: 9: /var/lib/dpkg/info/compiz.config: profile: not found /var/lib/dpkg/info/compiz.config: 11: /var/lib/dpkg/info/compiz.config: [general_ubuntu]: not found /var/lib/dpkg/info/compiz.config: 12: /var/lib/dpkg/info/compiz.config: backend: not found /var/lib/dpkg/info/compiz.config: 13: /var/lib/dpkg/info/compiz.config: integration: not found /var/lib/dpkg/info/compiz.config: 14: /var/lib/dpkg/info/compiz.config: plugin_list_autosort: not found /var/lib/dpkg/info/compiz.config: 15: /var/lib/dpkg/info/compiz.config: profile: not found

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  • C#/.NET Little Wonders: The ConcurrentDictionary

    - by James Michael Hare
    Once again we consider some of the lesser known classes and keywords of C#.  In this series of posts, we will discuss how the concurrent collections have been developed to help alleviate these multi-threading concerns.  Last week’s post began with a general introduction and discussed the ConcurrentStack<T> and ConcurrentQueue<T>.  Today's post discusses the ConcurrentDictionary<T> (originally I had intended to discuss ConcurrentBag this week as well, but ConcurrentDictionary had enough information to create a very full post on its own!).  Finally next week, we shall close with a discussion of the ConcurrentBag<T> and BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. Recap As you'll recall from the previous post, the original collections were object-based containers that accomplished synchronization through a Synchronized member.  While these were convenient because you didn't have to worry about writing your own synchronization logic, they were a bit too finely grained and if you needed to perform multiple operations under one lock, the automatic synchronization didn't buy much. With the advent of .NET 2.0, the original collections were succeeded by the generic collections which are fully type-safe, but eschew automatic synchronization.  This cuts both ways in that you have a lot more control as a developer over when and how fine-grained you want to synchronize, but on the other hand if you just want simple synchronization it creates more work. With .NET 4.0, we get the best of both worlds in generic collections.  A new breed of collections was born called the concurrent collections in the System.Collections.Concurrent namespace.  These amazing collections are fine-tuned to have best overall performance for situations requiring concurrent access.  They are not meant to replace the generic collections, but to simply be an alternative to creating your own locking mechanisms. Among those concurrent collections were the ConcurrentStack<T> and ConcurrentQueue<T> which provide classic LIFO and FIFO collections with a concurrent twist.  As we saw, some of the traditional methods that required calls to be made in a certain order (like checking for not IsEmpty before calling Pop()) were replaced in favor of an umbrella operation that combined both under one lock (like TryPop()). Now, let's take a look at the next in our series of concurrent collections!For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here. ConcurrentDictionary – the fully thread-safe dictionary The ConcurrentDictionary<TKey,TValue> is the thread-safe counterpart to the generic Dictionary<TKey, TValue> collection.  Obviously, both are designed for quick – O(1) – lookups of data based on a key.  If you think of algorithms where you need lightning fast lookups of data and don’t care whether the data is maintained in any particular ordering or not, the unsorted dictionaries are generally the best way to go. Note: as a side note, there are sorted implementations of IDictionary, namely SortedDictionary and SortedList which are stored as an ordered tree and a ordered list respectively.  While these are not as fast as the non-sorted dictionaries – they are O(log2 n) – they are a great combination of both speed and ordering -- and still greatly outperform a linear search. Now, once again keep in mind that if all you need to do is load a collection once and then allow multi-threaded reading you do not need any locking.  Examples of this tend to be situations where you load a lookup or translation table once at program start, then keep it in memory for read-only reference.  In such cases locking is completely non-productive. However, most of the time when we need a concurrent dictionary we are interleaving both reads and updates.  This is where the ConcurrentDictionary really shines!  It achieves its thread-safety with no common lock to improve efficiency.  It actually uses a series of locks to provide concurrent updates, and has lockless reads!  This means that the ConcurrentDictionary gets even more efficient the higher the ratio of reads-to-writes you have. ConcurrentDictionary and Dictionary differences For the most part, the ConcurrentDictionary<TKey,TValue> behaves like it’s Dictionary<TKey,TValue> counterpart with a few differences.  Some notable examples of which are: Add() does not exist in the concurrent dictionary. This means you must use TryAdd(), AddOrUpdate(), or GetOrAdd().  It also means that you can’t use a collection initializer with the concurrent dictionary. TryAdd() replaced Add() to attempt atomic, safe adds. Because Add() only succeeds if the item doesn’t already exist, we need an atomic operation to check if the item exists, and if not add it while still under an atomic lock. TryUpdate() was added to attempt atomic, safe updates. If we want to update an item, we must make sure it exists first and that the original value is what we expected it to be.  If all these are true, we can update the item under one atomic step. TryRemove() was added to attempt atomic, safe removes. To safely attempt to remove a value we need to see if the key exists first, this checks for existence and removes under an atomic lock. AddOrUpdate() was added to attempt an thread-safe “upsert”. There are many times where you want to insert into a dictionary if the key doesn’t exist, or update the value if it does.  This allows you to make a thread-safe add-or-update. GetOrAdd() was added to attempt an thread-safe query/insert. Sometimes, you want to query for whether an item exists in the cache, and if it doesn’t insert a starting value for it.  This allows you to get the value if it exists and insert if not. Count, Keys, Values properties take a snapshot of the dictionary. Accessing these properties may interfere with add and update performance and should be used with caution. ToArray() returns a static snapshot of the dictionary. That is, the dictionary is locked, and then copied to an array as a O(n) operation.  GetEnumerator() is thread-safe and efficient, but allows dirty reads. Because reads require no locking, you can safely iterate over the contents of the dictionary.  The only downside is that, depending on timing, you may get dirty reads. Dirty reads during iteration The last point on GetEnumerator() bears some explanation.  Picture a scenario in which you call GetEnumerator() (or iterate using a foreach, etc.) and then, during that iteration the dictionary gets updated.  This may not sound like a big deal, but it can lead to inconsistent results if used incorrectly.  The problem is that items you already iterated over that are updated a split second after don’t show the update, but items that you iterate over that were updated a split second before do show the update.  Thus you may get a combination of items that are “stale” because you iterated before the update, and “fresh” because they were updated after GetEnumerator() but before the iteration reached them. Let’s illustrate with an example, let’s say you load up a concurrent dictionary like this: 1: // load up a dictionary. 2: var dictionary = new ConcurrentDictionary<string, int>(); 3:  4: dictionary["A"] = 1; 5: dictionary["B"] = 2; 6: dictionary["C"] = 3; 7: dictionary["D"] = 4; 8: dictionary["E"] = 5; 9: dictionary["F"] = 6; Then you have one task (using the wonderful TPL!) to iterate using dirty reads: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); And one task to attempt updates in a separate thread (probably): 1: // attempt updates in a separate thread 2: var updateTask = new Task(() => 3: { 4: // iterates, and updates the value by one 5: foreach (var pair in dictionary) 6: { 7: dictionary[pair.Key] = pair.Value + 1; 8: } 9: }); Now that we’ve done this, we can fire up both tasks and wait for them to complete: 1: // start both tasks 2: updateTask.Start(); 3: iterationTask.Start(); 4:  5: // wait for both to complete. 6: Task.WaitAll(updateTask, iterationTask); Now, if I you didn’t know about the dirty reads, you may have expected to see the iteration before the updates (such as A:1, B:2, C:3, D:4, E:5, F:6).  However, because the reads are dirty, we will quite possibly get a combination of some updated, some original.  My own run netted this result: 1: F:6 2: E:6 3: D:5 4: C:4 5: B:3 6: A:2 Note that, of course, iteration is not in order because ConcurrentDictionary, like Dictionary, is unordered.  Also note that both E and F show the value 6.  This is because the output task reached F before the update, but the updates for the rest of the items occurred before their output (probably because console output is very slow, comparatively). If we want to always guarantee that we will get a consistent snapshot to iterate over (that is, at the point we ask for it we see precisely what is in the dictionary and no subsequent updates during iteration), we should iterate over a call to ToArray() instead: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary.ToArray()) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); The atomic Try…() methods As you can imagine TryAdd() and TryRemove() have few surprises.  Both first check the existence of the item to determine if it can be added or removed based on whether or not the key currently exists in the dictionary: 1: // try add attempts an add and returns false if it already exists 2: if (dictionary.TryAdd("G", 7)) 3: Console.WriteLine("G did not exist, now inserted with 7"); 4: else 5: Console.WriteLine("G already existed, insert failed."); TryRemove() also has the virtue of returning the value portion of the removed entry matching the given key: 1: // attempt to remove the value, if it exists it is removed and the original is returned 2: int removedValue; 3: if (dictionary.TryRemove("C", out removedValue)) 4: Console.WriteLine("Removed C and its value was " + removedValue); 5: else 6: Console.WriteLine("C did not exist, remove failed."); Now TryUpdate() is an interesting creature.  You might think from it’s name that TryUpdate() first checks for an item’s existence, and then updates if the item exists, otherwise it returns false.  Well, note quite... It turns out when you call TryUpdate() on a concurrent dictionary, you pass it not only the new value you want it to have, but also the value you expected it to have before the update.  If the item exists in the dictionary, and it has the value you expected, it will update it to the new value atomically and return true.  If the item is not in the dictionary or does not have the value you expected, it is not modified and false is returned. 1: // attempt to update the value, if it exists and if it has the expected original value 2: if (dictionary.TryUpdate("G", 42, 7)) 3: Console.WriteLine("G existed and was 7, now it's 42."); 4: else 5: Console.WriteLine("G either didn't exist, or wasn't 7."); The composite Add methods The ConcurrentDictionary also has composite add methods that can be used to perform updates and gets, with an add if the item is not existing at the time of the update or get. The first of these, AddOrUpdate(), allows you to add a new item to the dictionary if it doesn’t exist, or update the existing item if it does.  For example, let’s say you are creating a dictionary of counts of stock ticker symbols you’ve subscribed to from a market data feed: 1: public sealed class SubscriptionManager 2: { 3: private readonly ConcurrentDictionary<string, int> _subscriptions = new ConcurrentDictionary<string, int>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public void AddSubscription(string tickerKey) 7: { 8: // add a new subscription with count of 1, or update existing count by 1 if exists 9: var resultCount = _subscriptions.AddOrUpdate(tickerKey, 1, (symbol, count) => count + 1); 10:  11: // now check the result to see if we just incremented the count, or inserted first count 12: if (resultCount == 1) 13: { 14: // subscribe to symbol... 15: } 16: } 17: } Notice the update value factory Func delegate.  If the key does not exist in the dictionary, the add value is used (in this case 1 representing the first subscription for this symbol), but if the key already exists, it passes the key and current value to the update delegate which computes the new value to be stored in the dictionary.  The return result of this operation is the value used (in our case: 1 if added, existing value + 1 if updated). Likewise, the GetOrAdd() allows you to attempt to retrieve a value from the dictionary, and if the value does not currently exist in the dictionary it will insert a value.  This can be handy in cases where perhaps you wish to cache data, and thus you would query the cache to see if the item exists, and if it doesn’t you would put the item into the cache for the first time: 1: public sealed class PriceCache 2: { 3: private readonly ConcurrentDictionary<string, double> _cache = new ConcurrentDictionary<string, double>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public double QueryPrice(string tickerKey) 7: { 8: // check for the price in the cache, if it doesn't exist it will call the delegate to create value. 9: return _cache.GetOrAdd(tickerKey, symbol => GetCurrentPrice(symbol)); 10: } 11:  12: private double GetCurrentPrice(string tickerKey) 13: { 14: // do code to calculate actual true price. 15: } 16: } There are other variations of these two methods which vary whether a value is provided or a factory delegate, but otherwise they work much the same. Oddities with the composite Add methods The AddOrUpdate() and GetOrAdd() methods are totally thread-safe, on this you may rely, but they are not atomic.  It is important to note that the methods that use delegates execute those delegates outside of the lock.  This was done intentionally so that a user delegate (of which the ConcurrentDictionary has no control of course) does not take too long and lock out other threads. This is not necessarily an issue, per se, but it is something you must consider in your design.  The main thing to consider is that your delegate may get called to generate an item, but that item may not be the one returned!  Consider this scenario: A calls GetOrAdd and sees that the key does not currently exist, so it calls the delegate.  Now thread B also calls GetOrAdd and also sees that the key does not currently exist, and for whatever reason in this race condition it’s delegate completes first and it adds its new value to the dictionary.  Now A is done and goes to get the lock, and now sees that the item now exists.  In this case even though it called the delegate to create the item, it will pitch it because an item arrived between the time it attempted to create one and it attempted to add it. Let’s illustrate, assume this totally contrived example program which has a dictionary of char to int.  And in this dictionary we want to store a char and it’s ordinal (that is, A = 1, B = 2, etc).  So for our value generator, we will simply increment the previous value in a thread-safe way (perhaps using Interlocked): 1: public static class Program 2: { 3: private static int _nextNumber = 0; 4:  5: // the holder of the char to ordinal 6: private static ConcurrentDictionary<char, int> _dictionary 7: = new ConcurrentDictionary<char, int>(); 8:  9: // get the next id value 10: public static int NextId 11: { 12: get { return Interlocked.Increment(ref _nextNumber); } 13: } Then, we add a method that will perform our insert: 1: public static void Inserter() 2: { 3: for (int i = 0; i < 26; i++) 4: { 5: _dictionary.GetOrAdd((char)('A' + i), key => NextId); 6: } 7: } Finally, we run our test by starting two tasks to do this work and get the results… 1: public static void Main() 2: { 3: // 3 tasks attempting to get/insert 4: var tasks = new List<Task> 5: { 6: new Task(Inserter), 7: new Task(Inserter) 8: }; 9:  10: tasks.ForEach(t => t.Start()); 11: Task.WaitAll(tasks.ToArray()); 12:  13: foreach (var pair in _dictionary.OrderBy(p => p.Key)) 14: { 15: Console.WriteLine(pair.Key + ":" + pair.Value); 16: } 17: } If you run this with only one task, you get the expected A:1, B:2, ..., Z:26.  But running this in parallel you will get something a bit more complex.  My run netted these results: 1: A:1 2: B:3 3: C:4 4: D:5 5: E:6 6: F:7 7: G:8 8: H:9 9: I:10 10: J:11 11: K:12 12: L:13 13: M:14 14: N:15 15: O:16 16: P:17 17: Q:18 18: R:19 19: S:20 20: T:21 21: U:22 22: V:23 23: W:24 24: X:25 25: Y:26 26: Z:27 Notice that B is 3?  This is most likely because both threads attempted to call GetOrAdd() at roughly the same time and both saw that B did not exist, thus they both called the generator and one thread got back 2 and the other got back 3.  However, only one of those threads can get the lock at a time for the actual insert, and thus the one that generated the 3 won and the 3 was inserted and the 2 got discarded.  This is why on these methods your factory delegates should be careful not to have any logic that would be unsafe if the value they generate will be pitched in favor of another item generated at roughly the same time.  As such, it is probably a good idea to keep those generators as stateless as possible. Summary The ConcurrentDictionary is a very efficient and thread-safe version of the Dictionary generic collection.  It has all the benefits of type-safety that it’s generic collection counterpart does, and in addition is extremely efficient especially when there are more reads than writes concurrently. Tweet Technorati Tags: C#, .NET, Concurrent Collections, Collections, Little Wonders, Black Rabbit Coder,James Michael Hare

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  • MySQL Cluster 7.3 Labs Release – Foreign Keys Are In!

    - by Mat Keep
    0 0 1 1097 6254 Homework 52 14 7337 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} Summary (aka TL/DR): Support for Foreign Key constraints has been one of the most requested feature enhancements for MySQL Cluster. We are therefore extremely excited to announce that Foreign Keys are part of the first Labs Release of MySQL Cluster 7.3 – available for download, evaluation and feedback now! (Select the mysql-cluster-7.3-labs-June-2012 build) In this blog, I will attempt to discuss the design rationale, implementation, configuration and steps to get started in evaluating the first MySQL Cluster 7.3 Labs Release. Pace of Innovation It was only a couple of months ago that we announced the General Availability (GA) of MySQL Cluster 7.2, delivering 1 billion Queries per Minute, with 70x higher cross-shard JOIN performance, Memcached NoSQL key-value API and cross-data center replication.  This release has been a huge hit, with downloads and deployments quickly reaching record levels. The announcement of the first MySQL Cluster 7.3 Early Access lab release at today's MySQL Innovation Day event demonstrates the continued pace in Cluster development, and provides an opportunity for the community to evaluate and feedback on new features they want to see. What’s the Plan for MySQL Cluster 7.3? Well, Foreign Keys, as you may have gathered by now (!), and this is the focus of this first Labs Release. As with MySQL Cluster 7.2, we plan to publish a series of preview releases for 7.3 that will incrementally add new candidate features for a final GA release (subject to usual safe harbor statement below*), including: - New NoSQL APIs; - Features to automate the configuration and provisioning of multi-node clusters, on premise or in the cloud; - Performance and scalability enhancements; - Taking advantage of features in the latest MySQL 5.x Server GA. Design Rationale MySQL Cluster is designed as a “Not-Only-SQL” database. It combines attributes that enable users to blend the best of both relational and NoSQL technologies into solutions that deliver web scalability with 99.999% availability and real-time performance, including: Concurrent NoSQL and SQL access to the database; Auto-sharding with simple scale-out across commodity hardware; Multi-master replication with failover and recovery both within and across data centers; Shared-nothing architecture with no single point of failure; Online scaling and schema changes; ACID compliance and support for complex queries, across shards. Native support for Foreign Key constraints enables users to extend the benefits of MySQL Cluster into a broader range of use-cases, including: - Packaged applications in areas such as eCommerce and Web Content Management that prescribe databases with Foreign Key support. - In-house developments benefiting from Foreign Key constraints to simplify data models and eliminate the additional application logic needed to maintain data consistency and integrity between tables. Implementation The Foreign Key functionality is implemented directly within MySQL Cluster’s data nodes, allowing any client API accessing the cluster to benefit from them – whether using SQL or one of the NoSQL interfaces (Memcached, C++, Java, JPA or HTTP/REST.) The core referential actions defined in the SQL:2003 standard are implemented: CASCADE RESTRICT NO ACTION SET NULL In addition, the MySQL Cluster implementation supports the online adding and dropping of Foreign Keys, ensuring the Cluster continues to serve both read and write requests during the operation. An important difference to note with the Foreign Key implementation in InnoDB is that MySQL Cluster does not support the updating of Primary Keys from within the Data Nodes themselves - instead the UPDATE is emulated with a DELETE followed by an INSERT operation. Therefore an UPDATE operation will return an error if the parent reference is using a Primary Key, unless using CASCADE action, in which case the delete operation will result in the corresponding rows in the child table being deleted. The Engineering team plans to change this behavior in a subsequent preview release. Also note that when using InnoDB "NO ACTION" is identical to "RESTRICT". In the case of MySQL Cluster “NO ACTION” means “deferred check”, i.e. the constraint is checked before commit, allowing user-defined triggers to automatically make changes in order to satisfy the Foreign Key constraints. Configuration There is nothing special you have to do here – Foreign Key constraint checking is enabled by default. If you intend to migrate existing tables from another database or storage engine, for example from InnoDB, there are a couple of best practices to observe: 1. Analyze the structure of the Foreign Key graph and run the ALTER TABLE ENGINE=NDB in the correct sequence to ensure constraints are enforced 2. Alternatively drop the Foreign Key constraints prior to the import process and then recreate when complete. Getting Started Read this blog for a demonstration of using Foreign Keys with MySQL Cluster.  You can download MySQL Cluster 7.3 Labs Release with Foreign Keys today - (select the mysql-cluster-7.3-labs-June-2012 build) If you are new to MySQL Cluster, the Getting Started guide will walk you through installing an evaluation cluster on a singe host (these guides reflect MySQL Cluster 7.2, but apply equally well to 7.3) Post any questions to the MySQL Cluster forum where our Engineering team will attempt to assist you. Post any bugs you find to the MySQL bug tracking system (select MySQL Cluster from the Category drop-down menu) And if you have any feedback, please post them to the Comments section of this blog. Summary MySQL Cluster 7.2 is the GA, production-ready release of MySQL Cluster. This first Labs Release of MySQL Cluster 7.3 gives you the opportunity to preview and evaluate future developments in the MySQL Cluster database, and we are very excited to be able to share that with you. Let us know how you get along with MySQL Cluster 7.3, and other features that you want to see in future releases. * Safe Harbor Statement This information is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

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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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