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• Active directory authentication for Ubuntu Linux login and cifs mounting home directories...

  - by Jamie

  I've configured my Ubuntu 10.04 Server LTS Beta 2 residing on a windows network to authenticate logins using active directory, then mount a windows share to serve as there home directory. Here is what I did starting from the initial installation of Ubuntu. Download and install Ubuntu Server 10.04 LTS Beta 2 Get updates # sudo apt-get update && sudo apt-get upgrade Install an SSH server (sshd) # sudo apt-get install openssh-server Some would argue that you should "lock sshd down" by disabling root logins. I figure if your smart enough to hack an ssh session for a root password, you're probably not going to be thwarted by the addition of PermitRootLogin no in the /etc/ssh/sshd_config file. If your paranoid or not simply not convinced then edit the file or give the following a spin: # (grep PermitRootLogin /etc/ssh/sshd_conifg && sudo sed -ri 's/PermitRootLogin ).+/\1no/' /etc/ssh/sshd_conifg) || echo "PermitRootLogin not found. Add it manually." Install required packages # sudo apt-get install winbind samba smbfs smbclient ntp krb5-user Do some basic networking housecleaning in preparation for the specific package configurations to come. Determine your windows domain name, DNS server name, and IP address for the active directory server (for samba). For conveniance I set environment variables for the windows domain and DNS server. For me it was (my AD IP address was 192.168.20.11): # WINDOMAIN=mydomain.local && WINDNS=srv1.$WINDOMAIN If you want to figure out what your domain and DNS server is (I was contractor and didn't know the network) check out this helpful reference. The authentication and file sharing processes for the Windows and Linux boxes need to have their clocks agree. Do this with an NTP service, and on the server version of Ubuntu the NTP service comes installed and preconfigured. The network I was joining had the DNS server serving up the NTP service too. # sudo sed -ri "s/^(server[ \t]).+/\1$WINDNS/" /etc/ntp.conf Restart the NTP daemon # sudo /etc/init.d/ntp restart We need to christen the Linux box on the new network, this is done by editing the host file (replace the DNS of with the FQDN of the windows DNS): # sudo sed -ri "s/^(127\.0\.0\.1[ \t]).*/\1$(hostname).$WINDOMAIN localhost $(hostname)/" /etc/hosts Kerberos configuration. The instructions that follow here aren't to be taken literally: the values for MYDOMAIN.LOCAL and srv1.mydomain.local need to be replaced with what's appropriate for your network when you edit the files. Edit the (previously installed above) /etc/krb5.conf file. Find the [libdefaults] section and change (or add) the key value pair (and it is in UPPERCASE WHERE IT NEEDS TO BE): [libdefaults] default_realm = MYDOMAIN.LOCAL Add the following to the [realms] section of the file: MYDOMAIN.LOCAL = { kdc = srv1.mydomain.local admin_server = srv1.mydomain.local default_domain = MYDOMAIN.LOCAL } Add the following to the [domain_realm] section of the file: .mydomain.local = MYDOMAIN.LOCAL mydomain.local = MYDOMAIN.LOCAL Conmfigure samba. When it's all said done, I don't know where SAMBA fits in ... I used cifs to mount the windows shares ... regardless, my system works and this is how I did it. Replace /etc/samba/smb.conf (remember I was working from a clean distro of Ubuntu, so I wasn't worried about breaking anything): [global] security = ads realm = MYDOMAIN.LOCAL password server = 192.168.20.11 workgroup = MYDOMAIN idmap uid = 10000-20000 idmap gid = 10000-20000 winbind enum users = yes winbind enum groups = yes template homedir = /home/%D/%U template shell = /bin/bash client use spnego = yes client ntlmv2 auth = yes encrypt passwords = yes winbind use default domain = yes restrict anonymous = 2 Start and stop various services. # sudo /etc/init.d/winbind stop # sudo service smbd restart # sudo /etc/init.d/winbind start Setup the authentication. Edit the /etc/nsswitch.conf. Here are the contents of mine: passwd: compat winbind group: compat winbind shadow: compat winbind hosts: files dns networks: files protocols: db files services: db files ethers: db files rpc: db files Start and stop various services. # sudo /etc/init.d/winbind stop # sudo service smbd restart # sudo /etc/init.d/winbind start At this point I could login, home directories didn't exist, but I could login. Later I'll come back and add how I got the cifs automounting to work. Numerous resources were considered so I could figure this out. Here is a short list (a number of these links point to mine own questions on the topic): Samba Kerberos Active Directory WinBind Mounting Linux user home directories on CIFS server Authenticating OpenBSD against Active Directory How to use Active Directory to authenticate linux users Mounting windows shares with Active Directory permissions Using Active Directory authentication with Samba on Ubuntu 9.10 server 64bit How practical is to authenticate a Linux server against AD? Auto-mounting a windows share on Linux AD login

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• C++: Declaration of template class member specialization

  - by Ziv

  When I specialize a (static) member function/constant in a template class, I'm confused as to where the declaration is meant to go. Here's an example of what I what to do - yoinked directly from IBM's reference on template specialization: ===IBM Member Specialization Example=== template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } int main() { X<char*> a, b; X<float> c; c.f(10); // X<float>::v now set to 20 } The question is, how do I divide this into header/cpp files? The generic implementation is obviously in the header, but what about the specialization? It can't go in the header file, because it's concrete, leading to multiple definition. But if it goes into the .cpp file, is code which calls X::f() aware of the specialization, or might it rely on the generic X::f()? So far I've got the specialization in the .cpp only, with no declaration in the header. I'm not having trouble compiling or even running my code (on gcc, don't remember the version at the moment), and it behaves as expected - recognizing the specialization. But A) I'm not sure this is correct, and I'd like to know what is, and B) my Doxygen documentation comes out wonky and very misleading (more on that in a moment a later question). What seems most natural to me would be something like this, declaring the specialization in the header and defining it in the .cpp: ===XClass.hpp=== #ifndef XCLASS_HPP #define XCLASS_HPP template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } /* declaration of specialized functions */ template<> char* X<char*>::v; template<> void X<float>::f(float arg); #endif ===XClass.cpp=== #include <XClass.hpp> /* concrete implementation of specialized functions */ template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } ...but I have no idea if this is correct. Any ideas? Thanks much, Ziv

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• Databinding to ObservableCollection in a different UserControl - how to preserve current selections?

  - by Dave

  Scope of question expanded on 2010-03-25 I ended up figuring out my problem, but here's a new problem that came up as a result of solving the original question, because I want to be able to award the bounty to someone!!! Once I figured out my problem, I soon found out that when the ObservableCollection updates, the databound ComboBox has its contents repopulated, but most of the selections have been blanked out. I assume that in this case, MVVM is going to make it difficult for me to remember the last selected item. I have an idea, but it seems a little nasty. I'll award the bounty to whomever comes up with a nice solution for this! Question re-written on 2010-03-24 I have two UserControls, where one is a dialog that has a TabControl, and the other is one that appears within said TabControl. I'll just call them CandyDialog and CandyNameViewer for simplicity's sake. There's also a data management class called Tracker that manages information storage, which for all intents and purposes just exposes a public property that is an ObservableCollection. I display the CandyNameViewer in CandyDialog via code behind, like this: private void CandyDialog_Loaded( object sender, RoutedEventArgs e) { _candyviewer = new CandyViewer(); _candyviewer.DataContext = _tracker; candy_tab.Content = _candyviewer; } The CandyViewer's XAML looks like this (edited for kaxaml): <Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> <Page.Resources> <DataTemplate x:Key="CandyItemTemplate"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="120"></ColumnDefinition> <ColumnDefinition Width="150"></ColumnDefinition> </Grid.ColumnDefinitions> <TextBox Grid.Column="0" Text="{Binding CandyName}" Margin="3"></TextBox> <!-- just binding to DataContext ends up using InventoryItem as parent, so we need to get to the UserControl --> <ComboBox Grid.Column="1" SelectedItem="{Binding SelectedCandy, Mode=TwoWay}" ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}, Path=DataContext.CandyNames}" Margin="3"></ComboBox> </Grid> </DataTemplate> </Page.Resources> <Grid> <ListBox DockPanel.Dock="Top" ItemsSource="{Binding CandyBoxContents, Mode=TwoWay}" ItemTemplate="{StaticResource CandyItemTemplate}" /> </Grid> </Page> Now everything works fine when the controls are loaded. As long as CandyNames is populated first, and then the consumer UserControl is displayed, all of the names are there. I obviously don't get any errors in the Output Window or anything like that. The issue I have is that when the ObservableCollection is modified from the model, those changes are not reflected in the consumer UserControl! I've never had this problem before; all of my previous uses of ObservableCollection updated fine, although in those cases I wasn't databinding across assemblies. Although I am currently only adding and removing candy names to/from the ObservableCollection, at a later date I will likely also allow renaming from the model side. Is there something I did wrong? Is there a good way to actually debug this? Reed Copsey indicates here that inter-UserControl databinding is possible. Unfortunately, my favorite Bea Stollnitz article on WPF databinding debugging doesn't suggest anything that I could use for this particular problem.

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• Optimizing MySQL for small VPS

  - by Chris M

  I'm trying to optimize my MySQL config for a verrry small VPS. The VPS is also running NGINX/PHP-FPM and Magento; all with a limit of 250MB of RAM. This is an output of MySQL Tuner... -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.1.41-3ubuntu12.8 [OK] Operating on 64-bit architecture -------- Storage Engine Statistics ------------------------------------------- [--] Status: -Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 1M (Tables: 14) [--] Data in InnoDB tables: 29M (Tables: 301) [--] Data in MEMORY tables: 1M (Tables: 17) [!!] Total fragmented tables: 301 -------- Security Recommendations ------------------------------------------- [OK] All database users have passwords assigned -------- Performance Metrics ------------------------------------------------- [--] Up for: 2d 11h 14m 58s (1M q [8.038 qps], 33K conn, TX: 2B, RX: 618M) [--] Reads / Writes: 83% / 17% [--] Total buffers: 122.0M global + 8.6M per thread (100 max threads) [!!] Maximum possible memory usage: 978.2M (404% of installed RAM) [OK] Slow queries: 0% (37/1M) [OK] Highest usage of available connections: 6% (6/100) [OK] Key buffer size / total MyISAM indexes: 32.0M/282.0K [OK] Key buffer hit rate: 99.7% (358K cached / 1K reads) [OK] Query cache efficiency: 83.4% (1M cached / 1M selects) [!!] Query cache prunes per day: 48301 [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 144K sorts) [OK] Temporary tables created on disk: 13% (27K on disk / 203K total) [OK] Thread cache hit rate: 99% (6 created / 33K connections) [!!] Table cache hit rate: 0% (32 open / 51K opened) [OK] Open file limit used: 1% (20/1K) [OK] Table locks acquired immediately: 99% (1M immediate / 1M locks) [!!] InnoDB data size / buffer pool: 29.2M/8.0M -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance Reduce your overall MySQL memory footprint for system stability Enable the slow query log to troubleshoot bad queries Increase table_cache gradually to avoid file descriptor limits Variables to adjust: *** MySQL's maximum memory usage is dangerously high *** *** Add RAM before increasing MySQL buffer variables *** query_cache_size (> 64M) table_cache (> 32) innodb_buffer_pool_size (>= 29M) and this is the config. # # 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 = 32M max_allowed_packet = 16M thread_stack = 192K thread_cache_size = 8 sort_buffer_size = 4M read_buffer_size = 4M myisam_sort_buffer_size = 16M # 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 = 32 tmp_table_size = 128M #thread_concurrency = 10 # # * Query Cache Configuration # #query_cache_limit = 1M query_cache_type = 1 query_cache_size = 64M # # * 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/ The site contains 1 wordpress site,so lots of MYISAM but mostly static content as its not changing all that often (A wordpress cache plugin deals with this). And the Magento Site which consists of a lot of InnoDB tables, some MyISAM and some INMEMORY. The "read" side seems to be running pretty well with a mass of optimizations I've used on Magento, the NGINX setup and PHP-FPM + XCACHE. I'd love to have a kick in the right direction with the MySQL config so I'm not blindly altering it based on the MySQLTuner without understanding what I'm changing. Thanks

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• An "elegant" way of identifying a field?

  - by Alix

  Hi. I'm writing a system that underlies programmer applications and that needs to detect their access to certain data. I can mostly do so with properties, like this: public class NiceClass { public int x { get; set; } } Then I go in and tweak the get and set accessors so that they handle the accesses appropriately. However this requires that the users (application programmers) define all of their data as properties. If the users want to use pre-existing classes that have "normal" fields (as opposed to properties), I cannot detect those accesses. Example: public class NotSoNiceClass { public int y; } I cannot detect accesses to y. However, I want to allow the use of pre-existing classes. As a compromise the users are responsible for notifying me whenever an access to that kind of data occurs. For example: NotSoNiceClass notSoNice; ... Write(notSoNice.y, 0); // (as opposed to notSoNice.y = 0;) Something like that. Believe me, I've researched this very thoroughly and even directly analysing the bytecode to detect accesses isn't reliable due to possible indirections, etc. I really do need the users to notify me. And now my question: could you recommend an "elegant" way to perform these notifications? (Yes, I know this whole situation isn't "elegant" to begin with; I'm trying not to make it worse ;) ). How would you do it? This is a problem for me because actually the situation is like this: I have the following class: public class SemiNiceClass { public NotSoNiceClass notSoNice { get; set; } public int z { get; set; } } If the user wants to do this: SemiNiceClass semiNice; ... semiNice.notSoNice.y = 0; They must instead do something like this: semiNice.Write("notSoNice").y = 0; Where Write will return a clone of notSoNice, which is what I wanted the set accessor to do anyway. However, using a string is pretty ugly: if later they refactor the field they'll have to go over their Write("notSoNice") accesses and change the string. How can we identify the field? I can only think of strings, ints and enums (i.e., ints again). But: We've already discussed the problem with strings. Ints are a pain. They're even worse because the user needs to remember which int corresponds to which field. Refactoring is equally difficult. Enums (such as NOT_SO_NICE and Z, i.e., the fields of SemiNiceClass) ease refactoring, but they require the user to write an enum per class (SemiNiceClass, etc), with a value per field of the class. It's annoying. I don't want them to hate me ;) So why, I hear you ask, can we not do this (below)? semiNice.Write(semiNice.notSoNice).y = 0; Because I need to know what field is being accessed, and semiNice.notSoNice doesn't identify a field. It's the value of the field, not the field itself. Sigh. I know this is ugly. Believe me ;) I'll greatly appreciate suggestions. Thanks in advance! (Also, I couldn't come up with good tags for this question. Please let me know if you have better ideas, and I'll edit them)

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• Problem installing Ubuntu 10.04 64 bit side by side with Vista by using a bootable USB drive. What n

  - by Adam Siddhi

  What happened I decided to install Ubuntu 10.04 64 bit side by side with Vista Home Premium (I guess on another partition) with a USB stick. I found instructions on how to do this here: https://help.ubuntu.com/community/Installation/FromUSBStick To create the bootable USB drive I had to download a program called Unetbootin. That process was simple enough. All I had to do was just choose the disk image option, select the ubuntu-10.04-desktop-amd64.iso image, make sure it recognizes my USB drive and then press OK. It takes only like a few minutes to create a working bootable USB drive. Then I have to restart my computer, enter the BIOS, select my USB drive as the first boot drive, save options and continue with booting up. After this Ubuntu actually loads up. I think this is known as the Live version of Ubuntu so you can try it out before fully installing it. Any ways, on the Ubuntu 10.04 desktop I saw an installer. I click it and begin the installation process. Just so you know, I tried installing it 2 times. I will explain what happened each time: The first time I tried installing Ubuntu 10.04 I got stuck at step 4 of 7. I remember selecting the last option in the window which was Specify Partitions Manually (Advanced) I made my partition for Ubuntu like 52 gigs. I clicked forward and a little pop up window appeared saying Please Wait. So the installation process stalled on this window so I closed out of it and quit the installation process. So at this point I was worried because I had already selected the partition size and assumed it started making it. Since it stalled I had to quit out though. Anyways, once again I reached step 4 of 7 a decided to select the first option which is Install them side by side choosing between them each startup. I figured this was the safe way to go. I did that and the pop up window saying Please Wait popped up again but lasted only like 10 seconds. Then I got to I guess step 6 where it asks you to enter your desired name and password. Did that and clicked forward. The Ubuntu 10.04 installation load screen appeared and the loading bar at the bottom started filling up. So I got to 83% and stalled during the Importing other profile information (I think it was called this. I had the option to do this during I think step 6) process. So at this point I decided to get stop the installation process. I was getting very nervous. I tried to restart the computer but all that happened was that Ubuntu restarted. I finally got the computer to restart. I was pretty sure I had screwed something up big time by this point. As my computer was restarting I entered BIOS again and switched back to it booting from my main hard drive containing Vista. Saved it and continued the boot process. My worst fears were confirmed as Vista would not boot up. I mean I saw the little Microsoft Windows choppy animated green loading bar at the bottom of the screen and then boom! It decided to restart. When it restarted I had the option to run a memory test check to see if there was anything that needed to be repaired. That took like 20 minutes and at the end I saw that I did indeed have to repair something. I had to go through 2 repair processes. After each I had to restart the computer. The 2nd time it went through the repair process it said that it could not fully repair the damage. I was scared and restarted but Vista did load up. I got to my desktop and saw a message saying something like Repairs have been made, Please restart for changes to take effect I noticed that some Notification icons were missing and I could not hear volume in a video. Things were a bit funky. So I did restart and here I am. Now what?! So since I got back into Vista and thankfully have a working Internet connection I am trying to find answers to my problem (that is why I am writing this post). I am scared that I have partioned my hard drive 2 times after researching Installing Ubuntu 10.04 and seeing this post http://techie-buzz.com/foss/ubuntu-10-04-lts-installation-guide.html The author shows screen shots of installing Ubuntu 10.04. He shows the image of step 4 of 7 with a caption at the bottom. I will recreate it below: Select a partitioning option. Unless you want to format all the hard drive and install Ubuntu afresh, select the last option and proceed. Questions If I have indeed partitioned my HD 2 times (which I am sure it is), how do I get to a point where I can see all my bad, unfinished Ubuntu partitions and get rid of them? How do I clean this big mess up? & How can I ensure that this mess will not happen next time I try installing Ubuntu 10.04? Thank you Adam

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• Unicast traffic between hosts on a switch leaving the switch by its uplink. Why?

  - by Rich Lafferty

  I have a weird thing happening on our network at my office which I can't quite get my head around. In particular I can't tell if it's a problem with a switch, or a problem with configuration. We have a Cisco SG300-52 switch (sw01) in the top of a rack in our server room, connected to another SG300-28 that acts as our core switch (core01). Both run layer 2 only, our firewalls do routing between VLANs. They have a dozen or so VLANs between them. Gi1 on sw01 is a trunk port connected to gi1 on core01. (Disclosure: There are other switches in our environment but I'm pretty sure I've isolated the problem down to these two. Happy to provide more info if necessary.) The behaviour I'm seeing is limited to one VLAN, vlan 12 -- or, at least, it's not happening on the other ones I checked (It's hard to guarantee the absence of packets), and it is: sw01 is forwarding, to core01, traffic which is between two hosts which are both plugged into sw01. (I noticed this because the IDS in our firewall gave a false positive on traffic which should not reach the firewall.) We noticed this mostly between our two dhcp/dns servers, net01 (10.12.0.10) and net02 (10.12.0.11). net01 is physical hardware and net02 is on a VMware ESX server. net01 is connected to gi44 on sw01 and net02's ESX server to gi11. [net01]----gi44-[sw01]-gi1----gi1-[core01] [net02]----gi11/ Let's see some interfaces! Remember, vlan 12 is the problem vlan. Of the others I explicitly verified that vlan 27 was not affected. Here's the two hosts' ports: esx01 contains net02. sw01#sh run int gi11 interface gigabitethernet11 description esx01 lldp med disable switchport trunk allowed vlan add 5-7,11-13,100 switchport trunk native vlan 27 ! sw01#sh run int gi44 interface gigabitethernet44 description net01-1 lldp med disable switchport mode access switchport access vlan 12 ! Here's the trunk on sw01. sw01#sh run int gi1 interface gigabitethernet1 description "trunk to core01" lldp med disable switchport trunk allowed vlan add 4-7,11-13,27,100 ! And the other end of the trunk on core01. interface gigabitethernet1 description sw01 macro description switch switchport trunk allowed vlan add 2-7,11-16,27,100 ! I have a monitor port on core01, thus: core01#sh run int gi12 interface gigabitethernet12 description "monitor port" port monitor GigabitEthernet 1 ! And the monitor port on core01 sees unicast traffic going between net01 and net02, both of which are on sw01! I've verified this with a monitor port on sw01 that sees the net01-net02 unicast traffic leaving via gi1 too. sw01 knows that both of those hosts are on ports that are not its trunk port: :) ratchet$ arp -a | grep net net02.2ndsiteinc.com (10.12.0.11) at 00:0C:29:1A:66:15 [ether] on eth0 net01.2ndsiteinc.com (10.12.0.10) at 00:11:43:D8:9F:94 [ether] on eth0 sw01#sh mac addr addr 00:0C:29:1A:66:15 Aging time is 300 sec Vlan Mac Address Port Type -------- --------------------- ---------- ---------- 12 00:0c:29:1a:66:15 gi11 dynamic sw01#sh mac addr addr 00:11:43:D8:9F:94 Aging time is 300 sec Vlan Mac Address Port Type -------- --------------------- ---------- ---------- 12 00:11:43:d8:9f:94 gi44 dynamic I also brought up an unused port on sw01 on vlan 12, but the unicast traffic was (as best as I could tell) not coming out that port. So it doesn't look like sw01 is pushing it out all its ports, just the right ports and also gi1! I've verified that sw01 is not filling up its address-table: sw01#sh mac addr count This may take some time. Capacity : 8192 Free : 7983 Used : 208 The full configs for both core01 and sw01 are available: core01, sw01. Finally, versions: sw01#sh ver SW version 1.1.2.0 ( date 12-Nov-2011 time 23:34:26 ) Boot version 1.0.0.4 ( date 08-Apr-2010 time 16:37:57 ) HW version V01 core01#sh ver SW version 1.1.2.0 ( date 12-Nov-2011 time 23:34:26 ) Boot version 1.1.0.6 ( date 11-May-2011 time 18:31:00 ) HW version V01 So my understanding is this: sw01 should take unicast traffic for net01 and send it only out net02's port, and vice versa; none of it should go out sw01's uplink. But core01, receiving traffic on gi1 for a host it knows is on gi1, is right in sending it out all of its ports. (That is: sw01 is misbehaving, but core01 is doing what it should given the circumstances.) My question is: Why is sw01 sending that unicast traffic out its uplink, gi1? (And pre-emptively: yes, I know SG300s leave much to be desired, and yes, we should have spanning-tree enabled, but that's where I'm at right now.)

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• Smart auto detect and replace URLs with anchor tags

  - by Robert Koritnik

  I've written a regular expression that automatically detects URLs in free text that users enter. This is not such a simple task as it may seem at first. Jeff Atwood writes about it in his post. His regular expression works, but needs extra code after detection is done. I've managed to write a regular expression that does everything in a single go. This is how it looks like (I've broken it down into separate lines to make it more understandable what it does): 1 (?<outer>\()? 2 (?<scheme>http(?<secure>s)?://)? 3 (?<url> 4 (?(scheme) 5 (?:www\.)? 6 | 7 www\. 8 ) 9 [a-z0-9] 10 (?(outer) 11 [-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+(?=\)) 12 | 13 [-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+ 14 ) 15 ) 16 (?<ending>(?(outer)\))) As you may see, I'm using named capture groups (used later in Regex.Replace()) and I've also included some local characters (cšžcd), that allow our localised URL to be parsed as well. You can easily omit them if you'd like. Anyway. Here's what it does (referring to line numbers): 1 - detects if URL starts with open braces (is contained inside braces) and stores it in "outer" named capture group 2 - checks if it starts with URL scheme also detecting whether scheme is SSL or not 3 - starts parsing URL itself (will store it in "url" named capture group) 4-8 - if statement that says: if "sheme" was present then www. part is optional, otherwise mandatory for a string to be a link (so this regular expression detects all strings that start with either http or www) 9 - first character after http:// or www. should be either a letter or a number (this can be extended if you would like to cover even more links, but I've decided to omit other characters because I can't remember a link that would start with some other character 10-14 - if statement that says: if "outer" (braces) was present capture everything up to the last closing braces otherwise capture all 15 - closes the named capture group for URL 16 - if open braces was present, capture closing braces as well and store it in "ending" named capture group First and last line used to have \s* in them as well, so user could also write open braces and put a space inside before pasting link. Anyway. My code that does link replacement with actual anchor HTML elements looks exactly like this: value = Regex.Replace( value, @"(?<outer>\()?(?<scheme>http(?<secure>s)?://)?(?<url>(?(scheme)(?:www\.)?|www\.)[a-z0-9](?(outer)[-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+(?=\))|[-a-z0-9/+&@#/%?=~_()|!:,.;cšžcd]+))(?<ending>(?(outer)\)))", "${outer}<a href=\"http${secure}://${url}\">http${secure}://${url}</a>${ending}", RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.IgnoreCase); As you can see I'm using named capture groups to replace link with an Anchor tag: ${outer}<a href=\"http${secure}://${url}\">http${secure}://${url}</a>${ending} I could as well omit the http(s) part in anchor display to make links look friendlier, but for now I decided not to. Question I would like for my links to be replaced with shortenings as well. So when user copies a very long links (for instance if they would copy a link from google maps that usually generates long links I would like to shorten the visible part of the anchor tag. Link would work, but visible part of an anchor tag would be shortened to some number of characters. Does the replace string support notations like that so I can stil use a singe Regex.Replace() call?

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• Error Handling without Exceptions

  - by James

  While searching SO for approaches to error handling related to business rule validation , all I encounter are examples of structured exception handling. MSDN and many other reputable development resources are very clear that exceptions are not to be used to handle routine error cases. They are only to be used for exceptional circumstances and unexpected errors that may occur from improper use by the programmer (but not the user.) In many cases, user errors such as fields that are left blank are common, and things which our program should expect, and therefore are not exceptional and not candidates for use of exceptions. QUOTE: Remember that the use of the term exception in programming has to do with the thinking that an exception should represent an exceptional condition. Exceptional conditions, by their very nature, do not normally occur; so your code should not throw exceptions as part of its everyday operations. Do not throw exceptions to signal commonly occurring events. Consider using alternate methods to communicate to a caller the occurrence of those events and leave the exception throwing for when something truly out of the ordinary happens. For example, proper use: private void DoSomething(string requiredParameter) { if (requiredParameter == null) throw new ArgumentExpcetion("requiredParameter cannot be null"); // Remainder of method body... } Improper use: // Renames item to a name supplied by the user. Name must begin with an "F". public void RenameItem(string newName) { // Items must have names that begin with "F" if (!newName.StartsWith("F")) throw new RenameException("New name must begin with /"F/""); // Remainder of method body... } In the above case, according to best practices, it would have been better to pass the error up to the UI without involving/requiring .NET's exception handling mechanisms. Using the same example above, suppose one were to need to enforce a set of naming rules against items. What approach would be best? Having the method return a enumerated result? RenameResult.Success, RenameResult.TooShort, RenameResult.TooLong, RenameResult.InvalidCharacters, etc. Using an event in a controller class to report to the UI class? The UI calls the controller's RenameItem method, and then handles an AfterRename event that the controller raises and that has rename status as part of the event args? The controlling class directly references and calls a method from the UI class that handles the error, e.g. ReportError(string text). Something else... ? Essentially, I want to know how to perform complex validation in classes that may not be the Form class itself, and pass the errors back to the Form class for display -- but I do not want to involve exception handling where it should not be used (even though it seems much easier!) Based on responses to the question, I feel that I'll have to state the problem in terms that are more concrete: UI = User Interface, BLL = Business Logic Layer (in this case, just a different class) User enters value within UI. UI reports value to BLL. BLL performs routine validation of the value. BLL discovers rule violation. BLL returns rule violation to UI. UI recieves return from BLL and reports error to user. Since it is routine for a user to enter invalid values, exceptions should not be used. What is the right way to do this without exceptions?

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• mdadm raid5 recover double disk failure - with a twist (drive order)

  - by Peter Bos

  Let me acknowledge first off that I have made mistakes, and that I have a backup for most but not all of the data on this RAID. I still have hope of recovering the rest of the data. I don't have the kind of money to take the drives to a recovery expert company. Mistake #0, not having a 100% backup. I know. I have a mdadm RAID5 system of 4x3TB. Drives /dev/sd[b-e], all with one partition /dev/sd[b-e]1. I'm aware that RAID5 on very large drives is risky, yet I did it anyway. Recent events The RAID become degraded after a two drive failure. One drive [/dev/sdc] is really gone, the other [/dev/sde] came back up after a power cycle, but was not automatically re-added to the RAID. So I was left with a 4 device RAID with only 2 active drives [/dev/sdb and /dev/sdd]. Mistake #1, not using dd copies of the drives for restoring the RAID. I did not have the drives or the time. Mistake #2, not making a backup of the superblock and mdadm -E of the remaining drives. Recovery attempt I reassembled the RAID in degraded mode with mdadm --assemble --force /dev/md0, using /dev/sd[bde]1. I could then access my data. I replaced /dev/sdc with a spare; empty; identical drive. I removed the old /dev/sdc1 from the RAID mdadm --fail /dev/md0 /dev/sdc1 Mistake #3, not doing this before replacing the drive I then partitioned the new /dev/sdc and added it to the RAID. mdadm --add /dev/md0 /dev/sdc1 It then began to restore the RAID. ETA 300 mins. I followed the process via /proc/mdstat to 2% and then went to do other stuff. Checking the result Several hours (but less then 300 mins) later, I checked the process. It had stopped due to a read error on /dev/sde1. Here is where the trouble really starts I then removed /dev/sde1 from the RAID and re-added it. I can't remember why I did this; it was late. mdadm --manage /dev/md0 --remove /dev/sde1 mdadm --manage /dev/md0 --add /dev/sde1 However, /dev/sde1 was now marked as spare. So I decided to recreate the whole array using --assume-clean using what I thought was the right order, and with /dev/sdc1 missing. mdadm --create /dev/md0 --assume-clean -l5 -n4 /dev/sdb1 missing /dev/sdd1 /dev/sde1 That worked, but the filesystem was not recognized while trying to mount. (It should have been EXT4). Device order I then checked a recent backup I had of /proc/mdstat, and I found the drive order. md0 : active raid5 sdb1[0] sde1[4] sdd1[2] sdc1[1] 8790402048 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU] I then remembered this RAID had suffered a drive loss about a year ago, and recovered from it by replacing the faulty drive with a spare one. That may have scrambled the device order a bit...so there was no drive [3] but only [0],[1],[2], and [4]. I tried to find the drive order with the Permute_array script: https://raid.wiki.kernel.org/index.php/Permute_array.pl but that did not find the right order. Questions I now have two main questions: I screwed up all the superblocks on the drives, but only gave: mdadm --create --assume-clean commands (so I should not have overwritten the data itself on /dev/sd[bde]1. Am I right that in theory the RAID can be restored [assuming for a moment that /dev/sde1 is ok] if I just find the right device order? Is it important that /dev/sde1 be given the device number [4] in the RAID? When I create it with mdadm --create /dev/md0 --assume-clean -l5 -n4 \ /dev/sdb1 missing /dev/sdd1 /dev/sde1 it is assigned the number [3]. I wonder if that is relevant to the calculation of the parity blocks. If it turns out to be important, how can I recreate the array with /dev/sdb1[0] missing[1] /dev/sdd1[2] /dev/sde1[4]? If I could get that to work I could start it in degraded mode and add the new drive /dev/sdc1 and let it resync again. It's OK if you would like to point out to me that this may not have been the best course of action, but you'll find that I realized this. It would be great if anyone has any suggestions.

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• Cross-platform distributed fault-tolerant (disconnected operation/local cache) filesystem

  - by Adrian Frühwirth

  We are facing a design "challenge" where we are required to set up a storage solution with the following properties: What we need HA a scalable storage backend offline/disconnected operation on the client to account for network outages cross-platform access client-side access from certainly Windows (probably XP upwards), possibly Linux backend integrates with AD/LDAP (permission management (user/group management, ...)) should work reasonably well over slow WAN-links Another problem is that we don't really know all possible use cases here, if people need to be able to have concurrent access to shared files or if they will only be accessing their own files, so a possible solution needs to account for concurrent access and how conflict management would look in this case from a user's point of view. This two years old blog posts sums up the impression that I have been getting during the last couple of days of research, that there are lots of current übercool projects implementing (non-Windows) clustered petabyte-capable blob-storage solutions but that there is none that supports disconnected operation nicely and natively, but I am hoping that we have missed an obvious solution. What we have tried OpenAFS We figured that we want a distributed network filesystem with a local cache and tested OpenAFS (which, as the only currently "stable" DFS supporting disconnected operation, seemed the way to go) for a week but there are several problems with it: it's a real pain to set up there are no official RHEL/CentOS packages the package of the current stable version 1.6.5.1 from elrepo randomly kernel panics on fresh installs, this is an absolute no-go Windows support (including the required Kerberos packages) is mystical. The current client for the 1.6 branch does not run on Windows 8, the current client for the 1.7 does but it just randomly crashes. After that experience we didn't even bother testing on XP and Windows 7. Suffice to say, we couldn't get it working and the whole setup has been so unstable and complicated to setup that it's just not an option for production. Samba + Unison Since OpenAFS was a complete disaster and no other DFS seems to support disconnected operation we went for a simpler idea that would sync files against a Samba server using Unison. This has the following advantages: Samba integrates with ADs; it's a pain but can be done. Samba solves the problem of remotely accessing the storage from Windows but introduces another SPOF and does not address the actual storage problem. We could probably stick any clustered FS underneath Samba, but that means we need a HA Samba setup on top of that to maintain HA which probably adds a lot of additional complexity. I vaguely remember trying to implement redundancy with Samba before and I could not silently failover between servers. Even when online, you are working with local files which will result in more conflicts than would be necessary if a local cache were only touched when disconnected It's not automatic. We cannot expect users to manually sync their files using the (functional, but not-so-pretty) GTK GUI on a regular basis. I attempted to semi-automate the process using the Windows task scheduler, but you cannot really do it in a satisfactory way. On top of that, the way Unison works makes syncing against Samba a costly operation, so I am afraid that it just doesn't scale very well or even at all. Samba + "Offline Files" After that we became a little desparate and gave Windows "offline files" a chance. We figured that having something that is inbuilt into the OS would reduce administrative efforts, helps blaming someone else when it's not working properly and should just work since people have been using this for years. Right? Wrong. We really wanted it to work, but it just doesn't. 30 minutes of copying files around and unplugging network cables/disabling network interfaces left us with (silent! there is only a tiny notification in Windows explorer in the statusbar, which doesn't even open Sync Center if you click on it!) undeletable files on the server (!) and conflicts that should not even be conflicts. In the end, we had one successful sync of a tiny text file, everything else just exploded horribly. Beyond that, there are other problems: Microsoft admits that "offline files" in Windows XP cannot cope with "large files" and therefore does not cache/sync them at all which would mean those files become unavailable if the connection drop In Windows 7 the feature is only available in the Professional/Ultimate/Enterprise editions. Summary Unless there is another fault-tolerant DFS that supports Windows natively I assume that stacking a HA Samba cluster on top of something like GlusterFS/Lustre/whatnot is the only option, but I hope that I am wrong here. How do other companies allow fault-tolerant network access to redundant storage in a heterogeneous environment with Windows?

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• How to query on table returned by Stored procedure within a procedure.

  - by Shantanu Gupta

  I have a stored procedure that is performing some ddl dml operations. It retrieves a data after processing data from CTE and cross apply and other such complex things. Now this returns me a 4 tables which gets binded to various sources at frontend. Now I want to use one of the table to further processing so as to get more usefull information from it. eg. This table would be containing approx 2000 records at most of which i want to get records that belongs to lodging only. PK_CATEGORY_ID DESCRIPTION FK_CATEGORY_ID IMMEDIATE_PARENT Department_ID Department_Name DESCRIPTION_HIERARCHY DEPTH IS_ACTIVE ID_PATH DESC_PATH -------------------- -------------------------------------------------- -------------------- -------------------------------------------------- -------------------- -------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------- ----------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1 Food NULL NULL 1 Food (Food) Food 0 1 0 Food 5 Chinese 1 Food 1 Food (Food) ----Chinese 1 1 1 Food->Chinese 14 X 5 Chinese 1 Food (Food) --------X 2 1 1->5 Food->Chinese->X 15 Y 5 Chinese 1 Food (Food) --------Y 2 1 1->5 Food->Chinese->Y 65 asdasd 5 Chinese 1 Food (Food) --------asdasd 2 1 1->5 Food->Chinese->asdasd 66 asdas 5 Chinese 1 Food (Food) --------asdas 2 1 1->5 Food->Chinese->asdas 8 Italian 1 Food 1 Food (Food) ----Italian 1 1 1 Food->Italian 48 hfghfgh 1 Food 1 Food (Food) ----hfghfgh 1 1 1 Food->hfghfgh 55 Asd 1 Food 1 Food (Food) ----Asd 1 1 1 Food->Asd 2 Lodging NULL NULL 2 Lodging (Lodging) Lodging 0 1 0 Lodging 3 Room 2 Lodging 2 Lodging (Lodging) ----Room 1 1 2 Lodging->Room 4 Floor 3 Room 2 Lodging (Lodging) --------Floor 2 1 2->3 Lodging->Room->Floor 9 First 4 Floor 2 Lodging (Lodging) ------------First 3 1 2->3->4 Lodging->Room->Floor->First 10 Second 4 Floor 2 Lodging (Lodging) ------------Second 3 1 2->3->4 Lodging->Room->Floor->Second 11 Third 4 Floor 2 Lodging (Lodging) ------------Third 3 1 2->3->4 Lodging->Room->Floor->Third 29 Fourth 4 Floor 2 Lodging (Lodging) ------------Fourth 3 1 2->3->4 Lodging->Room->Floor->Fourth 12 Air Conditioned 3 Room 2 Lodging (Lodging) --------Air Conditioned 2 1 2->3 Lodging->Room->Air Conditioned 20 With Balcony 12 Air Conditioned 2 Lodging (Lodging) ------------With Balcony 3 1 2->3->12 Lodging->Room->Air Conditioned->With Balcony 24 Mountain View 20 With Balcony 2 Lodging (Lodging) ----------------Mountain View 4 1 2->3->12->20 Lodging->Room->Air Conditioned->With Balcony->Mountain View 25 Ocean View 20 With Balcony 2 Lodging (Lodging) ----------------Ocean View 4 1 2->3->12->20 Lodging->Room->Air Conditioned->With Balcony->Ocean View 26 Garden View 20 With Balcony 2 Lodging (Lodging) ----------------Garden View 4 1 2->3->12->20 Lodging->Room->Air Conditioned->With Balcony->Garden View 52 Smoking 20 With Balcony 2 Lodging (Lodging) ----------------Smoking 4 1 2->3->12->20 Lodging->Room->Air Conditioned->With Balcony->Smoking 21 Without Balcony 12 Air Conditioned 2 Lodging (Lodging) ------------Without Balcony 3 1 2->3->12 Lodging->Room->Air Conditioned->Without Balcony 13 Non Air Conditioned 3 Room 2 Lodging (Lodging) --------Non Air Conditioned 2 1 2->3 Lodging->Room->Non Air Conditioned 22 With Balcony 13 Non Air Conditioned 2 Lodging (Lodging) ------------With Balcony 3 1 2->3->13 Lodging->Room->Non Air Conditioned->With Balcony 71 EA 3 Room 2 Lodging (Lodging) --------EA 2 1 2->3 Lodging->Room->EA 50 Casabellas 2 Lodging 2 Lodging (Lodging) ----Casabellas 1 1 2 Lodging->Casabellas 51 North Beach 50 Casabellas 2 Lodging (Lodging) --------North Beach 2 1 2->50 Lodging->Casabellas->North Beach 40 Fooding NULL NULL 40 Fooding (Fooding) Fooding 0 1 0 Fooding 41 Pizza 40 Fooding 40 Fooding (Fooding) ----Pizza 1 1 40 Fooding->Pizza 45 Onion 41 Pizza 40 Fooding (Fooding) --------Onion 2 1 40->41 Fooding->Pizza->Onion 47 Extra Cheeze 41 Pizza 40 Fooding (Fooding) --------Extra Cheeze 2 1 40->41 Fooding->Pizza->Extra Cheeze 77 Burger 40 Fooding 40 Fooding (Fooding) ----Burger 1 1 40 Fooding->Burger This result is being obtained to me using some stored procedure which contains some DML operations as well. i want something like this select description from exec spName where fk_category_id=5 Remember that this spName is returning me 4 tables of which i want to perform some query on one of the table whose index will be known to me. I dont have to send it to UI before querying further. I am using Sql Server 2008 but would like a compatible solution for 2005 also.

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• Rendering a view to a string in MVC, then redirecting -- workarounds?

  - by James S

  Hi -- I can't render a view to a string and then redirect, despite this answer from Feb (after version 1.0, I think) that claims it's possible. I thought I was doing something wrong, and then I read this answer from Haack in July that claims it's not possible. If somebody has it working and can help me get it working, that's great (and I'll post code, errors). However, I'm now at the point of needing workarounds. There are a few, but nothing ideal. Has anybody solved this, or have any comments on my ideas? This is to render email. While I can surely send the email outside of the web request (store info in a db and get it later), there are many types of emails and I don't want to store the template data (user object, a few other LINQ objects) in a db to let it get rendered later. I could create a simpler, serializable POCO and save that in the db, but why? ... I just want rendered text! I can create a new RedirectToAction object that checks if the headers have been sent (can't figure out how to do this -- try/catch?) and, if so, builds out a simple page with a meta redirect, a javascript redirect, and also a "click here" link. Within my controller, I can remember if I've rendered an email and, if so, manually do #2 by displaying a view. I can manually send the redirect headers before any potential email rendering. Then, rather than using the MVC infrastructure to redirecttoaction, I just call result.end. This seems easiest, but really messy. Anything else? EDIT: I've tried Dan's code (very similar to the code from Jan/Feb that I've already tried) and I'm still getting the same error. The only substantial difference I can see is that his example uses a view while I use a partial view. I'll try testing this later with a view. Here's what I've got: Controller public ActionResult Certifications(string email_intro) { //a lot of stuff ViewData["users"] = users; if (isPost()) { //create the viewmodel var view_model = new ViewModels.Emails.Certifications.Open(userContext) { emailIntro = email_intro }; //i've tried stopping this after just one iteration, in case the problem is due to calling it multiple times foreach (var user in users) { if (user.Email_Address.IsValidEmailAddress()) { //add more stuff to the view model specific to this user view_model.user = user; view_model.certification302Summary.subProcessesOwner = new SubProcess_Certifications(RecordUpdating.Role.Owner, null, null, user.User_ID, repository); //more here.... //if i comment out the next line, everything works ok SendEmail(view_model, this.ControllerContext); } } return RedirectToAction("Certifications"); } return View(); } SendEmail() public static void SendEmail(ViewModels.Emails.Certifications.Open model, ControllerContext context) { var vd = context.Controller.ViewData; vd["model"] = model; var renderer = new CustomRenderers(); //i fixed an error in your code here var text = renderer.RenderViewToString3(context, "~/Views/Emails/Certifications/Open.ascx", "", vd, null); var a = text; } CustomRenderers public class CustomRenderers { public virtual string RenderViewToString3(ControllerContext controllerContext, string viewPath, string masterPath, ViewDataDictionary viewData, TempDataDictionary tempData) { //copy/paste of dan's code } } Error [HttpException (0x80004005): Cannot redirect after HTTP headers have been sent.] System.Web.HttpResponse.Redirect(String url, Boolean endResponse) +8707691 Thanks, James

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• Writing a code example

  - by Stefano Borini

  I would like to have your feedback regarding code examples. One of the most frustrating experiences I sometimes have when learning a new technology is finding useless examples. I think an example as the most precious thing that comes with a new library, language, or technology. It must be a starting point, a wise and unadulterated explanation on how to achieve a given result. A perfect example must have the following characteristics: Self contained: it should be small enough to be compiled or executed as a single program, without dependencies or complex makefiles. An example is also a strong functional test if you correctly installed the new technology. The more issues could arise, the more likely is that something goes wrong, and the more difficult is to debug and solve the situation. Pertinent: it should demonstrate one, and only one, specific feature of your software/library, involving the minimal additional behavior from external libraries. Helpful: the code should bring you forward, step by step, using comments or self-documenting code. Extensible: the example code should be a small “framework” or blueprint for additional tinkering. A learner can start by adding features to this blueprint. Recyclable: it should be possible to extract parts of the example to use in your own code Easy: An example code is not the place to show your code-fu skillz. Keep it easy. helpful acronym: SPHERE. Prototypical examples of violations of those rules are the following: Violation of self-containedness: an example spanning multiple files without any real need for it. If your example is a python program, keep everything into a single module file. Don’t sub-modularize it. In Java, try to keep everything into a single class, unless you really must partition some entity into a meaningful object you need to pass around (and java mandates one class per file, if I remember correctly). Violation of Pertinency: When showing how many different shapes you can draw, adding radio buttons and complex controls with all the possible choices for point shapes is a bad idea. You de-focalize your example code, introducing code for event handling, controls initialization etc., and this is not part the feature you want to demonstrate, they are unnecessary noise in the understanding of the crucial mechanisms providing the feature. Violation of Helpfulness: code containing dubious naming, wrong comments, hacks, and functions longer than one page of code. Violation of Extensibility: badly factored code that have everything into a single function, with potentially swappable entities embedded within the code. Example: if an example reads data from a file and displays it, create a method getData() returning a useful entity, instead of opening the file raw and plotting the stuff. This way, if the user of the library needs to read data from a HTTP server instead, he just has to modify the getData() module and use the example almost as-is. Another violation of Extensibility comes if the example code is not under a fully liberal (e.g. MIT or BSD) license. Violation of Recyclability: when the code layout is so intermingled that is difficult to easily copy and paste parts of it and recycle them into another program. Again, licensing is also a factor. Violation of Easiness: Yes, you are a functional-programming nerd and want to show how cool you are by doing everything on a single line of map, filter and so on, but that could not be helpful to someone else, who is already under pressure to understand your library, and now has to understand your code as well. And in general, the final rule: if it takes more than 10 minutes to do the following: compile the code, run it, read the source, and understand it fully, it means that the example is not a good one. Please let me know your opinion, either positive or negative, or experience on this regard.

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• Is it possible to implement bitwise operators using integer arithmetic?

  - by Statement

  Hello World! I am facing a rather peculiar problem. I am working on a compiler for an architecture that doesn't support bitwise operations. However, it handles signed 16 bit integer arithmetics and I was wondering if it would be possible to implement bitwise operations using only: Addition (c = a + b) Subtraction (c = a - b) Division (c = a / b) Multiplication (c = a * b) Modulus (c = a % b) Minimum (c = min(a, b)) Maximum (c = max(a, b)) Comparisons (c = (a < b), c = (a == b), c = (a <= b), et.c.) Jumps (goto, for, et.c.) The bitwise operations I want to be able to support are: Or (c = a | b) And (c = a & b) Xor (c = a ^ b) Left Shift (c = a << b) Right Shift (c = a b) (All integers are signed so this is a problem) Signed Shift (c = a b) One's Complement (a = ~b) (Already found a solution, see below) Normally the problem is the other way around; how to achieve arithmetic optimizations using bitwise hacks. However not in this case. Writable memory is very scarce on this architecture, hence the need for bitwise operations. The bitwise functions themselves should not use a lot of temporary variables. However, constant read-only data & instruction memory is abundant. A side note here also is that jumps and branches are not expensive and all data is readily cached. Jumps cost half the cycles as arithmetic (including load/store) instructions do. On other words, all of the above supported functions cost twice the cycles of a single jump. Some thoughts that might help: I figured out that you can do one's complement (negate bits) with the following code: // Bitwise one's complement b = ~a; // Arithmetic one's complement b = -1 - a; I also remember the old shift hack when dividing with a power of two so the bitwise shift can be expressed as: // Bitwise left shift b = a << 4; // Arithmetic left shift b = a * 16; // 2^4 = 16 // Signed right shift b = a >>> 4; // Arithmetic right shift b = a / 16; For the rest of the bitwise operations I am slightly clueless. I wish the architects of this architecture would have supplied bit-operations. I would also like to know if there is a fast/easy way of computing the power of two (for shift operations) without using a memory data table. A naive solution would be to jump into a field of multiplications: b = 1; switch (a) { case 15: b = b * 2; case 14: b = b * 2; // ... exploting fallthrough (instruction memory is magnitudes larger) case 2: b = b * 2; case 1: b = b * 2; } Or a Set & Jump approach: switch (a) { case 15: b = 32768; break; case 14: b = 16384; break; // ... exploiting the fact that a jump is faster than one additional mul // at the cost of doubling the instruction memory footprint. case 2: b = 4; break; case 1: b = 2; break; }

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• Adding interactions to admin pages generated by the admin generator

  - by Stick it to THE MAN

  I am using Symfony 1.2.9 (with Propel ORM) to create a website. I have started using the admin generator to implement the admin functionality. I have come accross a slight 'problem' however. My models are related (e.g. one table may have several 1:N relations and N:N relations). I have not found a way to address this satisfactorily yet. As a tactical solution (for list views), I have decided to simply show the parent object, and then add interactions to show the related objects. I'll use a Blog model to illustrate this. Here are the relationships for a blog model: N:M relationship with Blogroll (models a blog roll) 1:N relationship with Blogpost (models a post submitted to a blog) I had originally intended on displaying the (paged) blogpost list for a blog,, when it was selected, using AJAX, but I am struggling enough with the admin generator as it is, so I have shelved that idea - unless someone is kind enough to shed some light on how to do this. Instead, what I am now doing (as a tactical/interim soln), is I have added interactions to the list view which allow a user to: View a list of the blog roll for the blog on that row View a list of the posts for the blog on that row Add a post for the blog on tha row In all of the above, I have written actions that will basically forward the request to the approriate action (admin generated). However, I need to pass some parameters (like the blog id etc), so that the correct blog roll or blog post list etc is returned. I am sure there is a better way of doing what I want to do, but in case there isn't here are my questions: How may I obtain the object that relates to a specific row (of the clicked link) in the list view (e.g. the blog object in this example) Once I have the object, I may choose to extract various fields: id etc. How can I pass these arguments to the admin generated action ? Regarding the second question, my guess is that this may be the way to do it (I may be wrong) public function executeMyAddedBlogRollInteractionLink(sfWebRequest $request) { // get the object *somehow* (I'm guessing this may work) $object = $this->getRoute()->getObject(); // retrieve the required parameters from the object, and build a query string $query_str=$object->getId(); //forward the request to the generated code (action to display blogroll list in this case) $this->forward('backendmodulename',"getblogrolllistaction?params=$query_string"); } This feels like a bit of a hack, but I'm not sure how else to go about it. I'm also not to keen on sending params (which may include user_id etc via a GET, even a POST is not that much safer, since it is fairly sraightforward to see what requests a browser is making). if there is a better way than what I suggest above to implement this kind of administration that is required for objects with 1 or more M:N relationships, I will be very glad to hear the "recommended" way of going about it. I remember reading about marking certain actions as internal. i.e. callable from only within the app. I wonder if that would be useful in this instance?

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• How to install MariaDB rpms in CentOS 6.4 using rpm (not yum cmd) + handling mysql-libs conflicts

  - by Pat C

  I need to script the install of MariaDB using the rpm command in CentOS 6.4. I can't use yum since it's going to be an offline install so there's no access to the repository. The only MySQL package installed is mysql-libs as various other packages in CentOS depend on it. When I did a test install of MariaDB with yum it correctly accounted for mysql-libs and uninstalled it at the end as MariaDB could handle the dependencies after it was installed: [root@new-host-6 ~]# yum install MariaDB-client MariaDB-common MariaDB-compat MariaDB-devel MariaDB-server MariaDB-shared Loaded plugins: downloadonly, fastestmirror, refresh-packagekit, security, verify Loading mirror speeds from cached hostfile * base: mirrors.kernel.org * extras: mirror.keystealth.org * updates: mirror.umd.edu Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package MariaDB-client.x86_64 0:5.5.32-1 will be installed ---> Package MariaDB-common.x86_64 0:5.5.32-1 will be installed ---> Package MariaDB-compat.x86_64 0:5.5.32-1 will be obsoleting ---> Package MariaDB-devel.x86_64 0:5.5.32-1 will be installed ---> Package MariaDB-server.x86_64 0:5.5.32-1 will be installed ---> Package MariaDB-shared.x86_64 0:5.5.32-1 will be obsoleting ---> Package mysql-libs.x86_64 0:5.1.66-2.el6_3 will be obsoleted --> Finished Dependency Resolution Dependencies Resolved ==================================================================================================================================================================== Package Arch Version Repository Size ==================================================================================================================================================================== Installing: MariaDB-client x86_64 5.5.32-1 mariadb 10 M MariaDB-common x86_64 5.5.32-1 mariadb 23 k MariaDB-compat x86_64 5.5.32-1 mariadb 2.7 M replacing mysql-libs.x86_64 5.1.66-2.el6_3 MariaDB-devel x86_64 5.5.32-1 mariadb 5.6 M MariaDB-server x86_64 5.5.32-1 mariadb 34 M MariaDB-shared x86_64 5.5.32-1 mariadb 1.1 M replacing mysql-libs.x86_64 5.1.66-2.el6_3 Transaction Summary ==================================================================================================================================================================== Install 6 Package(s) Total download size: 53 M Is this ok [y/N]: y Downloading Packages: (1/6): MariaDB-5.5.32-centos6-x86_64-client.rpm | 10 MB 00:06 (2/6): MariaDB-5.5.32-centos6-x86_64-common.rpm | 23 kB 00:00 (3/6): MariaDB-5.5.32-centos6-x86_64-compat.rpm | 2.7 MB 00:02 (4/6): MariaDB-5.5.32-centos6-x86_64-devel.rpm | 5.6 MB 00:06 (5/6): MariaDB-5.5.32-centos6-x86_64-server.rpm | 34 MB 00:23 (6/6): MariaDB-5.5.32-centos6-x86_64-shared.rpm | 1.1 MB 00:00 -------------------------------------------------------------------------------------------------------------------------------------------------------------------- Total 1.3 MB/s | 53 MB 00:40 warning: rpmts_HdrFromFdno: Header V4 DSA/SHA1 Signature, key ID 1bb943db: NOKEY Retrieving key from https://yum.mariadb.org/RPM-GPG-KEY-MariaDB Importing GPG key 0x1BB943DB: Userid: "Daniel Bartholomew (Monty Program signing key) <[email protected]>" From : https://yum.mariadb.org/RPM-GPG-KEY-MariaDB Is this ok [y/N]: y Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Warning: RPMDB altered outside of yum. Installing : MariaDB-compat-5.5.32-1.x86_64 1/7 Installing : MariaDB-common-5.5.32-1.x86_64 2/7 Installing : MariaDB-server-5.5.32-1.x86_64 3/7 chown: cannot access `/var/lib/mysql': No such file or directory PLEASE REMEMBER TO SET A PASSWORD FOR THE MariaDB root USER ! To do so, start the server, then issue the following commands: '/usr/bin/mysqladmin' -u root password 'new-password' '/usr/bin/mysqladmin' -u root -h new-host-6 password 'new-password' Alternatively you can run: '/usr/bin/mysql_secure_installation' which will also give you the option of removing the test databases and anonymous user created by default. This is strongly recommended for production servers. See the MariaDB Knowledgebase at http://kb.askmonty.org or the MySQL manual for more instructions. Please report any problems with the '/usr/bin/mysqlbug' script! The latest information about MariaDB is available at http://mariadb.org/. You can find additional information about the MySQL part at: http://dev.mysql.com Support MariaDB development by buying support/new features from Monty Program Ab. You can contact us about this at [email protected]. Alternatively consider joining our community based development effort: http://kb.askmonty.org/en/contributing-to-the-mariadb-project/ Installing : MariaDB-devel-5.5.32-1.x86_64 4/7 Installing : MariaDB-client-5.5.32-1.x86_64 5/7 Installing : MariaDB-shared-5.5.32-1.x86_64 6/7 Erasing : mysql-libs-5.1.66-2.el6_3.x86_64 7/7 Verifying : MariaDB-common-5.5.32-1.x86_64 1/7 Verifying : MariaDB-server-5.5.32-1.x86_64 2/7 Verifying : MariaDB-devel-5.5.32-1.x86_64 3/7 Verifying : MariaDB-client-5.5.32-1.x86_64 4/7 Verifying : MariaDB-compat-5.5.32-1.x86_64 5/7 Verifying : MariaDB-shared-5.5.32-1.x86_64 6/7 Verifying : mysql-libs-5.1.66-2.el6_3.x86_64 7/7 Installed: MariaDB-client.x86_64 0:5.5.32-1 MariaDB-common.x86_64 0:5.5.32-1 MariaDB-compat.x86_64 0:5.5.32-1 MariaDB-devel.x86_64 0:5.5.32-1 MariaDB-server.x86_64 0:5.5.32-1 MariaDB-shared.x86_64 0:5.5.32-1 Replaced: mysql-libs.x86_64 0:5.1.66-2.el6_3 Complete! My question is, what is the equivalent way to install the MariaDB packages using the rpm command only as opposed to yum? If I do rpm -ivh MariaDB*.rpm, I will get a ton of messages like the following about conflicts with mysql-libs: file /etc/my.cnf from install of MariaDB-common-5.5.32-1.x86_64 conflicts with file from package mysql-libs-5.1.66-2.el6_3.x86_64 file /usr/share/mysql/charsets/Index.xml from install of MariaDB-common-5.5.32-1.x86_64 conflicts with file from package mysql-libs-5.1.66-2.el6_3.x86_64 I then used the --force option to install the MariaDB rpms and uninstalled mysql-lib, I didn't get any weird messages but I'm not sure that is the cleanest method to handle the conflicts and do the install. So can someone confirm that installing MariaDB with the following rpm commands would be the same as using yum to install the packages and handle mysql-libs conflicts/removal: rpm -ivh --force MariaDB*.rpm rpm -e mysql-libs Thanks for any input!

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• Anyone willing to help out a javascript n00b? :-)

  - by Splynx

  Since I am asking for a lot, and know it, the following is a wall of text for those who might show some interest and want to know a little before offering their help to me. First a little about my level of programming skills, and a little about what I ask for. Where I'm at: I am not totally new to Javascript, and have dabbled a little with PHP earlier - well have dabbled a lot with PHP in fact, but never got good at it because I program alone. And I have until now never used forums to get help etc. other that searching to see if anyone else had my problem before and what the solution was. So I am not a intuitive or talented programmer, I'm more of a very maticulate programmer and you would be surprised how far you can get with if else... (ok that's a joke hehe). My solutions are usually (I am guessing here) not the best ones - and slow I take it, and the code is usually too long and I have to look up most of the stuff I use (really a lot of it is not done in "freehand"). I have a LOT of experience with HTML and CSS, and have always done well formed markup, as well as I am really into x-browsing and always require that my work validates when it's done. I also worry about optimizing a lot, and work with sprites for images, minimize the number of http requests etc, using H1,H2 etc. where it is logically correct, as well as use the correct elements and not just div span or p it... So because I am a workhorse and very maticulate I can actually pull off some quite "advanced" features, but it's always the basics that bite me in the end. Not fully understanding the syntax and so on usually gives me problems. Have recently discovered jQuery - wich is a lot of fun.... But I want to use it for the DOM node manipulation/handling only. As I mentioned I worry about optimizing, and jQuery used for everything seems... well not optimal, it strikes me as doing it yourself when possible is faster than accesing another script that may take a whole lot of other considerations into perspective when handling your variables and objects (and I am just guessing here since I as explained know nothing). So thats where I'm at... As mentioned I just started with javascript for "real" so I do not have much to show, but at the end of my WOT you can see two unfinisheded scripts I have made so you can see where I'm at roughly - just check out the URL without the /feedback.html for the second example (I am only allowed to post 1 link since I am also a SO n00b) (and for those rushing over to a validation service, remember I wrote "when it's done"...) What I ask for: I am figuring this... I have a piece of code I am working on at the moment, and this little project has taught me a whole lot already, and I have "grown" a lot as a javascript programmer. If I add a whole lot of comments to the script, and explain what it is intended to do, will you then show me where: I am writing incorrect code - making mistakes Where/how my code could be more optimal Where I am just simply being a muppet The code I want to use as the background for the tuition is the one here http://projects.1000monkeys.dk/feedback.html Use firebug and have a quick look see...

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• Remote host: can tracert, can telnet, can*not* browse: what gives?

  - by MacThePenguin

  One of my customers of the company I work for has made a change to their Internet connection, and now we can't connect to them any more from our LAN. To help me troubleshoot this issue, the network guy on the customer's site has configured their firewall so that a HTTPS connection to their public IP address is open to any IP. I should put https://<customer's IP> in my browser and get a web page. Well, it works from any network I've tried (even from my smartphone), just not from my company's LAN. I thought it may be an issue with our firewall (though I checked its rules and it allows outbound TCP port 443 to anywhere), so I just connected a PC directly to the network connection of our provider, bypassing out firewall completely, and still it didn't work (everything else worked). So I asked for help to our Internet provider's customer service, and they asked me to do a tracert to our customer's IP. The tracert is successful, as the final hop shown in the output is the host I want to reach. So they said there's no problem. :( I also tried telnet <customer's IP> 443 and that works as well: I get a blank page with the cursor blinking (I've tried using another random port and that gives me an error message, as it should). Still, from any browser of any PC in my LAN I can't open that URL. I tried checking the network traffic with Wireshark: I see the packages going through and answers coming back, thought the packets I see passing are far less than they are if I successfully connect to another HTTPS website. See the attached screenshot: I had to blur the IPs, anyway the longer string is my PC's local IP address, the shorter one is the customer's public IP. I don't know what else to try. This is the only IP doing this... Any idea what could I try to find a solution to this issue? Thanks, let me know if you need further details. Edit: when I say "it doesn't work" I mean: the page doesn't open, the browser keeps loading for a long time and eventually shows an error saying that the page cannot be opened. I'm not in my office now so I can't paste the exact message, but it's the usual message you get when the browser reaches its timeout. When I say "it works", I mean the browser loads and shows a webpage (it's the logon page for the customers' firewall admin interface: so there's the firewall brand's logo and there are fields to enter a user id and a password). Update 13/09/2012: tried again to connect to the customer's network through our Internet connection without a firewall. This is what I did: Run a Kubuntu 12.04 live distro on a spare laptop; Updated all the packages I could and installed WireShark; Attached it to my LAN and verified that I couldn't open https://<customer's IP>. Verified that the Wireshark trace for this attempt was the same as the one I've already posted; Verified that I could connect to another customer's host using rdesktop (it worked); Tried to rdesktop to <customer's IP>, here's the output: kubuntu@kubuntu:/etc$ rdesktop <customer's IP> Autoselected keyboard map en-us ERROR: recv: Connection reset by peer Disconnected the laptop from the LAN; Disconnected the firewall from the Extranet connection, connected the laptop instead. Set its network configuration so that I could access the Internet; Verified that I could connect to other websites in http and https and in RDP to other customers' hosts - it all worked as expected; Verified that I could still traceroute to <customer's IP>: I could; Verified that I still couldn't open https://<customer's IP> (same exact result as before); Checked the WireShark trace for this attempt and noticed a different behaviour: I could see packets going out to the customer's IP, but no replies at all; Tried to run rdesktop again, with a slightly different result: kubuntu@kubuntu:/etc/network$ rdesktop <customer's IP> Autoselected keyboard map en-us ERROR: <customer's IP>: unable to connect Finally gave up, put everything back as it was before, turned off the laptop and lost the WireShark traces I had saved. :( I still remember them very well though. :) Can you get anything out of it? Thank you very much. Update 12/09/2012 n.2: I followed the suggestion by MadHatter in the comments. From inside the firewall, this is what I get: user@ubuntu-mantis:~$ openssl s_client -connect <customer's IP>:443 CONNECTED(00000003) If I now type GET / the output pauses for several seconds and then I get: write:errno=104 I'm going to try the same, but bypassing the firewall, as soon as I can. Thanks. Update 12/09/2012 n.3: So, I think ISA Server is altering the results of my tests... I tried installing Wireshark directly on the firewall and monitoring the packets on the Extranet network card. When the destination is the customer's IP, whatever service I try to connect to (HTTPS, RDP or SAProuter), I can only see outbound packets and no response packets whatsoever from their side. It looks like ISA Server is "faking" the remote server's replies, that's why I get a connection using telnet or the openSSL client. This is the wireshark trace from inside our LAN: But this is the trace on the Extranet network card: This makes a bit more sense... I'll send this info to the customer's tech and see if he can make anything out of it. Thanks to all that took the time to read my question and post suggestions. I'll update this post again.

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• Cannot Logout of Facebook with Facebook C# SDK

  - by Ryan Smyth

  I think I've read just about everything out there on the topic of logging out of Facebook inside of a Desktop application. Nothing so far works. Specifically, I would like to log the user out so that they can switch identities, e.g. People sharing a computer at home could then use the software with their own Facebook accounts, but with no chance to switch accounts, it's quite messy. (Have not yet tested switching Windows users accounts as that is simply far too much to ask of the end user and should not be necessary.) Now, I should say that I have set the application to use these permissions: string[] permissions = new string[] { "user_photos", "publish_stream", "offline_access" }; So, "offline_access" is included there. I do not know if this does/should affect logging out or not. Again, my purpose for logging out is merely to switch users. (If there's a better approach, please let me know.) The purported solutions seem to be: Use the JavaScript SDK (FB.logout()) Use "m.facebook.com" instead Create your own URL (and possibly use m.facebook.com) Create your own URL and use the session variable (in ASP.NET) The first is kind of silly. Why resort to JavaScript when you're using C#? It's kind of a step backwards and has a lot of additional overhead in a desktop application. (I have not tried this as it's simply disgustingly messy to do this in a desktop application.) If anyone can confirm that this is the only working method, please do so. I'm desperately trying to avoid it. The second doesn't work. Perhaps it worked in the past, but my umpteen attempts to get it to work have all failed. The third doesn't work. I've tried umpteen dozen variations with zero success. The last option there doesn't work for a desktop application because it's not ASP.NET and you don't have a session variable to work with. The Facebook C# SDK logout also no longer works. i.e. public FacebookLoginDialog(string appId, string[] extendedPermissions, bool logout) { IDictionary<string, object> loginParameters = new Dictionary<string, object> { { "response_type", "token" }, { "display", "popup" } }; _navigateUri = FacebookOAuthClient.GetLoginUrl(appId, null, extendedPermissions, logout, loginParameters); InitializeComponent(); } I remember it working in the past, but it no longer works now. (Which truly puzzles me...) It instead now directs the user to the Facebook mobile page, where the user must manually logout. Now, I could do browser automation to automatically click the logout link for the user, however, this is prone to breaking if Facebook updates the mobile UI. It is also messy, and possibly a worse solution than trying to use the JavaScript SDK FB.logout() method (though not by much). I have searched for some kind of documentation, however, I cannot find anything in the Facebook developer documentation that illustrates how to logout an application. Has anyone solved this problem, or seen any documentation that can be ported to work with the Facebook C# SDK? I am certainly open to using a WebClient or HttpClient/Response if anyone can point to some documentation that could work with it. I simply have not been able to find any low-level documentation that shows how this approach could work. Thank you in advance for any advice, pointers, or links.

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• Why does my Ajax function returns my entire code?

  - by JDelage

  I'm playing with sample code from the book "Head first Ajax". Here are the salient pieces of code: Index.php - html piece: <body> <div id="wrapper"> <div id="thumbnailPane"> <img src="images/itemGuitar.jpg" width="301" height="105" alt="guitar" title="itemGuitar" id="itemGuitar" onclick="getDetails(this)"/> <img src="images/itemShades.jpg" alt="sunglasses" width="301" height="88" title="itemShades" id="itemShades" onclick="getDetails(this)" /> <img src="images/itemCowbell.jpg" alt="cowbell" width="301" height="126" title="itemCowbell" id="itemCowbell" onclick="getDetails(this)" /> <img src="images/itemHat.jpg" alt="hat" width="300" height="152" title="itemHat" id="itemHat" onclick="getDetails(this)" /> </div> <div id="detailsPane"> <img src="images/blank-detail.jpg" width="346" height="153" id="itemDetail" /> <div id="description"></div> </div> </div> </body> Index.php - script: function getDetails(img){ var title = img.title; request = createRequest(); if (request == null) { alert("Unable to create request"); return; } var url= "getDetails.php?ImageID=" + escape(title); request.open("GET", url, true); request.onreadystatechange = displayDetails; request.send(null); } function displayDetails() { if (request.readyState == 4) { if (request.status == 200) { detailDiv = document.getElementById("description"); detailDiv.innerHTML = request.responseText; }else{ return; } }else{ return; } request.send(null); } And Index.php: <?php $details = array ( 'itemGuitar' => "<p>Pete Townshend once played this guitar while his own axe was in the shop having bits of drumkit removed from it.</p>", 'itemShades' => "<p>Yoko Ono's sunglasses. While perhaps not valued much by Beatles fans, this pair is rumored to have been licked by John Lennon.</p>", 'itemCowbell' => "<p>Remember the famous \"more cowbell\" skit from Saturday Night Live? Well, this is the actual cowbell.</p>", 'itemHat' => "<p>Michael Jackson's hat, as worn in the \"Billie Jean\" video. Not really rock memorabilia, but it smells better than Slash's tophat.</p>" ); if (isset($_REQUEST['ImageID'])){echo $details[$_REQUEST['ImageID']];} ?> All this code does is that when someone clicks on a thumbnail, a corresponding text description appears on the page. Here is my question. I have tried to bring the getDetails.php code inside Index.php, and modify the getDetails function so that the var url be "Index.php?ImageID="... . When I do that, I get the following problem: the function does not display the snippet of text in the array, as it should. Instead it reproduces the entire code - the webpage, etc - and then at the bottom the expected snippet of text. Why is that?

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• Is it possible to embed Cockburn style textual UML Use Case content in the code base to improve code

  - by fooledbyprimes

  experimenting with Cockburn use cases in code I was writing some complicated UI code. I decided to employ Cockburn use cases with fish,kite,and sea levels (discussed by Martin Fowler in his book 'UML Distilled'). I wrapped Cockburn use cases in static C# objects so that I could test logical conditions against static constants which represented steps in a UI workflow. The idea was that you could read the code and know what it was doing because the wrapped objects and their public contants gave you ENGLISH use cases via namespaces. Also, I was going to use reflection to pump out error messages that included the described use cases. The idea is that the stack trace could include some UI use case steps IN ENGLISH.... It turned out to be a fun way to achieve a mini,psuedo light-weight Domain Language but without having to write a DSL compiler. So my question is whether or not this is a good way to do this? Has anyone out there ever done something similar? c# example snippets follow Assume we have some aspx page which has 3 user controls (with lots of clickable stuff). User must click on stuff in one particular user control (possibly making some kind of selection) and then the UI must visually cue the user that the selection was successful. Now, while that item is selected, the user must browse through a gridview to find an item within one of the other user controls and then select something. This sounds like an easy thing to manage but the code can get ugly. In my case, the user controls all sent event messages which were captured by the main page. This way, the page acted like a central processor of UI events and could keep track of what happens when the user is clicking around. So, in the main aspx page, we capture the first user control's event. using MyCompany.MyApp.Web.UseCases; protected void MyFirstUserControl_SomeUIWorkflowRequestCommingIn(object sender, EventArgs e) { // some code here to respond and make "state" changes or whatever // // blah blah blah // finally we have this (how did we know to call fish level method?? because we knew when we wrote the code to send the event in the user control) UpdateUserInterfaceOnFishLevelUseCaseGoalSuccess(FishLevel.SomeNamedUIWorkflow.SelectedItemForPurchase) } protected void UpdateUserInterfaceOnFishLevelGoalSuccess(FishLevel.SomeNamedUIWorkflow goal) { switch (goal) { case FishLevel.SomeNamedUIWorkflow.NewMasterItemSelected: //call some UI related methods here including methods for the other user controls if necessary.... break; case FishLevel.SomeNamedUIWorkFlow.DrillDownOnDetails: //call some UI related methods here including methods for the other user controls if necessary.... break; case FishLevel.SomeNamedUIWorkFlow.CancelMultiSelect: //call some UI related methods here including methods for the other user controls if necessary.... break; // more cases... } } } //also we have protected void UpdateUserInterfaceOnSeaLevelGoalSuccess(SeaLevel.SomeNamedUIWorkflow goal) { switch (goal) { case SeaLevel.CheckOutWorkflow.ChangedCreditCard: // do stuff // more cases... } } } So, in the MyCompany.MyApp.Web.UseCases namespace we might have code like this: class SeaLevel... class FishLevel... class KiteLevel... The workflow use cases embedded in the classes could be inner classes or static methods or enumerations or whatever gives you the cleanest namespace. I can't remember what I did originally but you get the picture.

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• C++/msvc6 application crashes due to heap corruption, any hints?

  - by David Alfonso

  Hello all, let me say first that I'm writing this question after months of trying to find out the root of a crash happening in our application. I'll try to detail as much as possible what I've already found out about it. About the application It runs on Windows XP Professional SP2. It's built with Microsoft Visual C++ 6.0 with Service Pack 6. It's MFC based. It uses several external dlls (e.g. Xerces, ZLib or ACE). It has high performance requirements. It does a lot of network and hard disk I/O, but it's also cpu intensive. It has an exception handling mechanism which generates a minidump when an unhandled exception occurs. Facts about the crash It only happens on multiprocessor/multicore machines and under heavy loads of work. It happens at random (neither we nor our client have found a pattern yet). We cannot reproduce the crash on our testing lab. It only happens on some production systems (but always in multicore machines) It always ends up crashing at the same point, although the complete stack is not always the same. Let me add the stack of the crashing thread (obtained using WinDbg, sorry we don't have symbols) ChildEBP RetAddr Args to Child WARNING: Stack unwind information not available. Following frames may be wrong. 030af6c8 7c9206eb 77bfc3c9 01a80000 00224bc3 MyApplication+0x2a85b9 030af960 7c91e9c0 7c92901b 00000ab4 00000000 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo]) 030af98c 7c9205c8 00000001 00000000 00000000 ntdll!ZwWaitForSingleObject+0xc (FPO: [3,0,0]) 030af9c0 7c920551 01a80898 7c92056d 313adfb0 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4]) 030afa8c 4ba3ae96 000307da 00130005 00040012 ntdll!RtlFreeHeap+0x1e9 (FPO: [Non-Fpo]) 030afacc 77bfc2e3 0214e384 3087c8d8 02151030 0x4ba3ae96 030afb00 7c91e306 7c80bfc1 00000948 00000001 msvcrt!free+0xc8 (FPO: [Non-Fpo]) 030afb20 0042965b 030afcc0 0214d780 02151218 ntdll!ZwReleaseSemaphore+0xc (FPO: [3,0,0]) 030afb7c 7c9206eb 02e6c471 02ea0000 00000008 MyApplication+0x2965b 030afe60 7c9205c8 02151248 030aff38 7c920551 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo]) 030afe74 7c92056d 0210bfb8 02151250 02151250 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4]) 030aff38 77bfc2de 01a80000 00000000 77bfc2e3 ntdll!RtlFreeHeap+0x647 (FPO: [Non-Fpo]) 7c92056d c5ffffff ce7c94be ff7c94be 00ffffff msvcrt!free+0xc3 (FPO: [Non-Fpo]) 7c920575 ff7c94be 00ffffff 12000000 907c94be 0xc5ffffff 7c920579 00ffffff 12000000 907c94be 90909090 0xff7c94be *** WARNING: Unable to verify checksum for xerces-c_2_7.dll *** ERROR: Symbol file could not be found. Defaulted to export symbols for xerces-c_2_7.dll - 7c92057d 12000000 907c94be 90909090 8b55ff8b MyApplication+0xbfffff 7c920581 907c94be 90909090 8b55ff8b 08458bec xerces_c_2_7 7c920585 90909090 8b55ff8b 08458bec 04408b66 0x907c94be 7c920589 8b55ff8b 08458bec 04408b66 0004c25d 0x90909090 7c92058d 08458bec 04408b66 0004c25d 90909090 0x8b55ff8b The address MyApplication+0x2a85b9 corresponds to a call to erase() of a std::list. What I have tried so far Reviewing all the code related to the point where the crash ends happening. Trying to enable pageheap on our testing lab though nothing useful has been found by now. We have substituted the std::list for a C array and then it crashes in other part of the code (although it is related code, it's not in the code where the old list resided). Coincidentally, now it crashes in another erase, though this time of a std::multiset. Let me copy the stack contained in the dump: ntdll.dll!_RtlpCoalesceFreeBlocks@16() + 0x124e bytes ntdll.dll!_RtlFreeHeap@12() + 0x91f bytes msvcrt.dll!_free() + 0xc3 bytes MyApplication.exe!006a4fda() [Frames below may be incorrect and/or missing, no symbols loaded for MyApplication.exe] MyApplication.exe!0069f305() ntdll.dll!_NtFreeVirtualMemory@16() + 0xc bytes ntdll.dll!_RtlpSecMemFreeVirtualMemory@16() + 0x1b bytes ntdll.dll!_ZwWaitForSingleObject@12() + 0xc bytes ntdll.dll!_RtlpFreeToHeapLookaside@8() + 0x26 bytes ntdll.dll!_RtlFreeHeap@12() + 0x114 bytes msvcrt.dll!_free() + 0xc3 bytes c5ffffff() Possible solutions (that I'm aware of) which cannot be applied "Migrate the application to a newer compiler": We are working on this but It's not a solution at the moment. "Enable pageheap (normal or full)": We can't enable pageheap on production machines as this affects performance heavily. I think that's all I remember now, if I have forgotten something I'll add it asap. If you can give me some hint or propose some possible solution, don't hesitate to answer! Thank you in advance for your time and advice.

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• Rails unknown action suddenly everywhere

  - by Joe

  The weird thing is that my app was working perfectly on Sat, and when I check it out on Monday (after doing nothing to it) I kept getting this problem: This behaviour is only happening on my production server. When I try to login or create a new user or do something that interacts with a form I am getting an unknown action error. A simple retrieval of rows does not throw this error however. I don't have all CRUD operations in most of my controllers because it's not necessary - but Rails always looks for the one that doesn't exist - it seams so anyway. If I make a mistake in the form that would normally throw a validation message to the user it will throw this error too, does that mean it has something to do with the model too (I'm not too Rails experienced and didn't know if that would be the case or not)? This is a general error I am getting - I have super_exception_notifier gem installed, so that's what all the extra params are. Processing SessionsController#new (for OMITTED at 2010-04-12 09:11:12) [GET] Rendering template within layouts/application Rendering sessions/new Completed in 3ms (View: 2, DB: 0) | 200 OK [http://OMITTED.com/session/new] Processing SessionsController#show (for OMITTED at 2010-04-12 09:11:14) [GET] ActionController::UnknownAction (No action responded to show. Actions: create, destroy, error_class_status_codes, error_class_status_codes=, error_layout, error_layout=, exception_notifiable_notification_level, exception_notifiable_notification_level=, exception_notifiable_silent_exceptions, exception_notifiable_silent_exceptions=, exception_notifiable_verbose, exception_notifiable_verbose=, http_status_codes, http_status_codes=, and new): dragonfly (0.5.3) lib/dragonfly/middleware.rb:13:in `call' passenger (2.2.9) lib/phusion_passenger/rack/request_handler.rb:92:in `process_request' passenger (2.2.9) lib/phusion_passenger/abstract_request_handler.rb:207:in `main_loop' passenger (2.2.9) lib/phusion_passenger/railz/application_spawner.rb:400:in `start_request_handler' passenger (2.2.9) lib/phusion_passenger/railz/application_spawner.rb:351:in `handle_spawn_application' passenger (2.2.9) lib/phusion_passenger/utils.rb:184:in `safe_fork' passenger (2.2.9) lib/phusion_passenger/railz/application_spawner.rb:349:in `handle_spawn_application' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:352:in `__send__' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:352:in `main_loop' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:163:in `start' passenger (2.2.9) lib/phusion_passenger/railz/application_spawner.rb:209:in `start' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:262:in `spawn_rails_application' passenger (2.2.9) lib/phusion_passenger/abstract_server_collection.rb:126:in `lookup_or_add' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:256:in `spawn_rails_application' passenger (2.2.9) lib/phusion_passenger/abstract_server_collection.rb:80:in `synchronize' passenger (2.2.9) lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:255:in `spawn_rails_application' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:154:in `spawn_application' passenger (2.2.9) lib/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:352:in `__send__' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:352:in `main_loop' passenger (2.2.9) lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously' This is what one of my forms looks like (nothing special) <% form_tag session_path do -%> <p><%= label_tag 'Username' %><br /> <%= text_field_tag 'login', @login %></p> <p><%= label_tag 'password' %><br/> <%= password_field_tag 'password', nil %></p> <p><%= label_tag 'remember_me', 'Remember me' %> <%= check_box_tag 'remember_me', '1', @remember_me %></p> <p><%= submit_tag 'Log in' %></p> <% end -%> It looks like dragonfly is the culprit doesn't it, here's the section from the gem files it says is being naughty: module Dragonfly class Middleware def initialize(app, dragonfly_app_name) @app = app @dragonfly_app_name = dragonfly_app_name end def call(env) response = endpoint.call(env) if response[0] == 404 13 -->> @app.call(env) else response end end I don't know what goes on behind the scenes here so I probably haven't been looking in the right place to fix this issue. Like I said it only throws this in a production environment, which guess is what the 'env' variable is referencing. Thank you for your time! I've spent nearly my whole day trying to figure this out! :(

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• Beginner question: ArrayList can't seem to get it right! Pls help

  - by elementz

  I have been staring at this code all day now, but just can't get it right. ATM I am just pushing codeblocks around without being able to concentrate anymore, with the due time being within almost an hour... So you guys are my last resort here. I am supposed to create a few random balls on a canvas, those balls being stored within an ArrayList (I hope an ArrayList is suitable here: the alternative options to choose from were HashSet and HashMap). Now, whatever I do, I get the differently colored balls at the top of my canvas, but they just get stuck there and refuse to move at all. Apart from that I now get a ConcurrentModificationException, when running the code: java.util.ConcurrentModificationException at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372) at java.util.AbstractList$Itr.next(AbstractList.java:343) at BallDemo.bounce(BallDemo.java:109) Reading up on that exception, I found out that one can make sure ArrayList is accessed in a threadsafe manner by somehow synchronizing access. But since I have remember fellow students doing without synchronizing, my guess is, that it would actually be the wrong path to go. Maybe you guys could help me get this to work, I at least need those stupid balls to move ;-) /** * Simulate random bouncing balls */ public void bounce(int count) { int ground = 400; // position of the ground line System.out.println(count); myCanvas.setVisible(true); // draw the ground myCanvas.drawLine(50, ground, 550, ground); // Create an ArrayList of type BouncingBalls ArrayList<BouncingBall>balls = new ArrayList<BouncingBall>(); for (int i = 0; i < count; i++){ Random numGen = new Random(); // Creating a random color. Color col = new Color(numGen.nextInt(256), numGen.nextInt(256), numGen.nextInt(256)); // creating a random x-coordinate for the balls int ballXpos = numGen.nextInt(550); BouncingBall bBall = new BouncingBall(ballXpos, 80, 20, col, ground, myCanvas); // adding balls to the ArrayList balls.add(bBall); bBall.draw(); boolean finished = false; } for (BouncingBall bBall : balls){ bBall.move(); } } This would be the original unmodified method we got from our teacher, which only creates two balls: /** * Simulate two bouncing balls */ public void bounce() { int ground = 400; // position of the ground line myCanvas.setVisible(true); myCanvas.drawLine(50, ground, 550, ground); // draw the ground // crate and show the balls BouncingBall ball = new BouncingBall(50, 50, 16, Color.blue, ground, myCanvas); ball.draw(); BouncingBall ball2 = new BouncingBall(70, 80, 20, Color.red, ground, myCanvas); ball2.draw(); // make them bounce boolean finished = false; while(!finished) { myCanvas.wait(50); // small delay ball.move(); ball2.move(); // stop once ball has travelled a certain distance on x axis if(ball.getXPosition() >= 550 && ball2.getXPosition() >= 550) { finished = true; } } ball.erase(); ball2.erase(); } }

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