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• Configure options MySQL server was compiled with?? [closed]

  - by GetFree

  I have MySQL server 5.0.67 running on a Linux machine. How can I know what configure options were used to compile it?? I'm interested in the option --with-mysqld-ldflags in order to know whether mysql was linked statically or dynamically. Thanks.

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• how to allow a remote machine to connect to a mysql database?

  - by iamrohitbanga

  I have a mysqld server running on a windows 7 machine. how to allow a windows vista machine to connect to this server. I need to set some permissions using grant all permissions to username@ip but what should be the username and ip. i am not sure with windows.

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• Which C# connector supports embedded MySql?

  - by pablo

  Hi, Do you know a .NET Connector that supports mysqld (embedded mysql)? AFAIK the official MySQL Connector/NET doesn't support it. Thanks

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• Is it possible to keep mysql migration running without keeping connection open?

  - by taw

  ALTER TABLE can easily take a few days - and during this time there's a non-negligible chance of connection getting terminated due to network problems. Is it possible to start ALTER TABLE (or CREATE TABLE ... SELECT ...; or some other very long running query) and leave it running without keeping connection open all the time? (the obvious solution of screen + console mysql client won't easily work as there's no ssh running on that server, only mysqld).

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• Can not set password for mysql server in cent os 6.2

  - by HarshanaD

  I have installed mysql and then mysql-server. Then i start the mysql demon and follow below steps, # chkconfig --level 2345 mysqld on # mysqladmin -u root password testpassword But i can not set the password because it gives me the below error, Access denied for user root@localhost (using password: no) I logged in as root user and perform those steps. I even uninstalled mysql server and reinstalled but same problem occurred.

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• Not able to create a datasource registration with WAMP MysQL 5.0 in DBArtisan

  - by Alf Christophersen

  I try in a test version of DBArtisan to set up a datasource and register both servere as localhost, database to use, my username and password, but, when testing the connection, I get message that connection failed. Hooking up from eg. Delphi and other utilities run nicely. But not DBArtisan, Is MySQL 5.0 not supported yet ?? Or is it WAMP that is the culprit naming the service wampmysqld insted of just mysqld ??

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• Can someone help me install MYSQL server pelase? This is bugging me....

  - by Alex

  $ sudo aptitude install mysql-server Reading package lists... Done Building dependency tree Reading state information... Done Reading extended state information Initializing package states... Done The following NEW packages will be installed: libhtml-template-perl{a} mysql-server mysql-server-5.0{a} mysql-server-core-5.0{a} 0 packages upgraded, 4 newly installed, 0 to remove and 12 not upgraded. Need to get 0B/27.7MB of archives. After unpacking 91.1MB will be used. Do you want to continue? [Y/n/?] y Writing extended state information... Done Preconfiguring packages ... Selecting previously deselected package mysql-server-core-5.0. (Reading database ... 17022 files and directories currently installed.) Unpacking mysql-server-core-5.0 (from .../mysql-server-core-5.0_5.1.30really5.0.75-0ubuntu10.3_amd64.deb) ... Selecting previously deselected package mysql-server-5.0. Unpacking mysql-server-5.0 (from .../mysql-server-5.0_5.1.30really5.0.75-0ubuntu10.3_amd64.deb) ... Selecting previously deselected package libhtml-template-perl. Unpacking libhtml-template-perl (from .../libhtml-template-perl_2.9-1_all.deb) ... Selecting previously deselected package mysql-server. Unpacking mysql-server (from .../mysql-server_5.1.30really5.0.75-0ubuntu10.3_all.deb) ... Setting up mysql-server-core-5.0 (5.1.30really5.0.75-0ubuntu10.3) ... Setting up mysql-server-5.0 (5.1.30really5.0.75-0ubuntu10.3) ... * Stopping MySQL database server mysqld [ OK ] /var/lib/dpkg/info/mysql-server-5.0.postinst: line 144: /etc/mysql/conf.d/old_passwords.cnf: No such file or directory dpkg: error processing mysql-server-5.0 (--configure): subprocess post-installation script returned error exit status 1 Setting up libhtml-template-perl (2.9-1) ... dpkg: dependency problems prevent configuration of mysql-server: mysql-server depends on mysql-server-5.0; however: Package mysql-server-5.0 is not configured yet. dpkg: error processing mysql-server (--configure): dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure. Errors were encountered while processing: mysql-server-5.0 mysql-server E: Sub-process /usr/bin/dpkg returned an error code (1) A package failed to install. Trying to recover: Setting up mysql-server-5.0 (5.1.30really5.0.75-0ubuntu10.3) ... * Stopping MySQL database server mysqld [ OK ] /var/lib/dpkg/info/mysql-server-5.0.postinst: line 144: /etc/mysql/conf.d/old_passwords.cnf: No such file or directory dpkg: error processing mysql-server-5.0 (--configure): subprocess post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of mysql-server: mysql-server depends on mysql-server-5.0; however: Package mysql-server-5.0 is not configured yet. dpkg: error processing mysql-server (--configure): dependency problems - leaving unconfigured Errors were encountered while processing: mysql-server-5.0 mysql-server Reading package lists... Done Building dependency tree Reading state information... Done Reading extended state information Initializing package states... Done Writing extended state information... Done Before I installed it, I ran this: sudo aptitude purge mysql-server mysql-server-5.0 This has happened before. I remember before, I did something with dpkg with fixed it.

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• Don&rsquo;t Kill the Password

  - by Anthony Trudeau

  A week ago Mr. Honan from Wired.com penned an article on security he titled “Kill the Password: Why a String of Characters Can’t Protect Us Anymore.” He asserts that the password is not effective and a new solution is needed. Unfortunately, Mr. Honan was a victim of hacking. As a result he has a victim’s vendetta. His conclusion is ill conceived even though there are smatterings of truth and good advice. The password is a security barrier much like a lock on your door. In of itself it’s not guaranteeing protection. You can have a good password akin to a steel reinforced door with the best lock money can buy, or you can have a poor password like “password” which is like a sliding lock like on a bathroom stall. But, just like in the real world a lock isn’t always enough. You can have a lock, security system, video cameras, guard dogs, and even armed security guards; but none of that guarantees your protection. Even top secret government agencies can be breached by someone who is just that good (as dramatized in movies like Mission Impossible). And that’s the crux of it. There are real hackers out there that are that good. Killer coding ninja monkeys do exist! We still have locks on our doors, because they still serve their role. Passwords are no different. Security doesn’t end with the password. Most people would agree that stuffing your mattress with your life savings isn’t a good idea even if you have the best locks and security system. Most people agree its safest to have the money in a bank. Essentially this is compartmentalization. Compartmentalization extends to the online world as well. You’re at risk if your online banking accounts are linked to the same account as your social networks. This is especially true if you’re lackadaisical about linking those social networks to outside sources including apps. The object here is to minimize the damage that can be done. An attacker should not be able to get into your bank account, because they breached your Twitter account. It’s time to prioritize once you’ve compartmentalized. This simply means deciding how much security you want for the different compartments which I’ll call security zones. Social networking applications like Facebook provide a lot of security features. However, security features are almost always a compromise with privacy and convenience. It’s similar to an engineering adage, but in this case it’s security, convenience, and privacy – pick two. For example, you might use a safe instead of bank to store your money, because the convenience of having your money closer or the privacy of not having the bank records is more important than the added security. The following are lists of security do’s and don’ts (these aren’t meant to be exhaustive and each could be an article in of themselves): Security Do’s: Use strong passwords based on a phrase Use encryption whenever you can (e.g. HTTPS in Facebook) Use a firewall (and learn to use it properly) Configure security on your router (including port blocking) Keep your operating system patched Make routine backups of important files Realize that if you’re not paying for it, you’re the product Security Don’ts Link accounts if at all possible Reuse passwords across your security zones Use real answers for security questions (e.g. mother’s maiden name) Trust anything you download Ignore message boxes shown by your system or browser Forget to test your backups Share your primary email indiscriminately Only you can decide your comfort level between convenience, privacy, and security. Attackers are going to find exploits in software. Software is complex and depends on other software. The exploits are the responsibility of the software company. But your security is always your responsibility. Complete security is an illusion. But, there is plenty you can do to minimize the risk online just like you do in the physical world. Be safe and enjoy what the Internet has to offer. I expect passwords to be necessary just as long as locks.

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• MySQL my.cnf file not being read, Ubuntu 10.04 64bit

  - by reallyordinary

  I've been researching this for a few hours with no luck. Basically it looks like my server's my.cnf file isn't being read at all. I've searched my server, and there's only one my.cnf file on it, located at /etc/mysql/my.cnf. Its ownership is root:root. I'm running Ubuntu 10.04 64bit on a Linode.com server. I have the latest versions of MySQL and PHP installed. I've edited the my.cnf file, commented out "skip-innodb", and have set innodb to be the default storage engine using default-storage-engine = innodb And then restarted mysql. But when I do show engines, MyISAM is still coming up as the default engine. Also - none of the innodb settings I've added to the my.cnf file are being read. For example, I have this in my.cnf: innodb_buffer_pool_size=4G But in phpmyadmin, InnoDB is showing as having a buffer pool size of 8,192 KiB. Similarly, I have this in the my.cnf: innodb_data-file_path = ibdata1:500M:autoextend But in phpmyadmin, it's reading as ibdata1:10M:autoextend. It doesn't look like MyISAM info is being read from the my.cnf file either. The my.cnf file has skip-external-locking queried out, but it's showing as "on" in phpmyadmin. So - yeah, it looks like nothing in the my.cnf file is being read at all. But the server still works. I'm running a Drupal site on it and it seems to operate fine. So mysql seems to be drawing default settings from... some mysterious secret location. Any idea how I can make mysql see and use this my.cnf file? Actually, wait - it looks like it may be being read, not sure. I checked the error.log and found this: 101128 4:28:52 [ERROR] Cannot find or open table databasename/cache_apachesolr from the internal data dictionary of InnoDB though the .frm file for the table exists. Maybe you have deleted and recreated InnoDB data files but have forgotten to delete the corresponding .frm files of InnoDB tables, or you have moved .frm files to another database? or, the table contains indexes that this version of the engine doesn't support. See http://dev.mysql.com/doc/refman/5.1/en/innodb-troubleshooting.html how you can resolve the problem. InnoDB: Error: auto-extending data file ./ibdata1 is of a different size InnoDB: 640 pages (rounded down to MB) than specified in the .cnf file: InnoDB: initial 32000 pages, max 0 (relevant if non-zero) pages! InnoDB: Could not open or create data files. InnoDB: If you tried to add new data files, and it failed here, InnoDB: you should now edit innodb_data_file_path in my.cnf back InnoDB: to what it was, and remove the new ibdata files InnoDB created InnoDB: in this failed attempt. InnoDB only wrote those files full of InnoDB: zeros, but did not yet use them in any way. But be careful: do not InnoDB: remove old data files which contain your precious data! 101128 4:28:52 [ERROR] Plugin 'InnoDB' init function returned error. 101128 4:28:52 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed. 101128 4:28:52 [ERROR] /usr/sbin/mysqld: unknown variable 'innodb_lock_wait_timout=50' 101128 4:28:52 [ERROR] Aborting 101128 4:28:52 [Note] /usr/sbin/mysqld: Shutdown complete

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• after enabling mod ssl apache stops listening on port 80

  - by zensys

  I have an ubuntu 12.04 server with zend server CE installed. I now wanted to enable https but after the first steps according to the documentation, 'a2enmod ssl' and 'apache service restart', apache does not listen on 443 but neither on 80, according to netstat -tap | grep http(s)! This is what I see in my error log, but I can't make much of it: [Fri May 25 19:52:39 2012] [notice] caught SIGTERM, shutting down [Fri May 25 19:52:41 2012] [warn] Init: Session Cache is not configured [hint: SSLSessionCache] [Fri May 25 19:52:41 2012] [notice] ModSecurity for Apache/2.6.3 (http://www.modsecurity.org/) configured. [Fri May 25 19:52:41 2012] [notice] ModSecurity: APR compiled version="1.4.5"; loaded version="1.4.6" [Fri May 25 19:52:41 2012] [warn] ModSecurity: Loaded APR do not match with compiled! [Fri May 25 19:52:41 2012] [notice] ModSecurity: PCRE compiled version="8.12"; loaded version="8.12 2011-01-15" [Fri May 25 19:52:41 2012] [notice] ModSecurity: LUA compiled version="Lua 5.1" [Fri May 25 19:52:41 2012] [notice] ModSecurity: LIBXML compiled version="2.7.8" [Fri May 25 19:53:11 2012] [notice] ModSecurity for Apache/2.6.3 (http://www.modsecurity.org/) configured. [Fri May 25 19:53:11 2012] [notice] ModSecurity: APR compiled version="1.4.5"; loaded version="1.4.6" [Fri May 25 19:53:11 2012] [warn] ModSecurity: Loaded APR do not match with compiled! [Fri May 25 19:53:11 2012] [notice] ModSecurity: PCRE compiled version="8.12"; loaded version="8.12 2011-01-15" [Fri May 25 19:53:11 2012] [notice] ModSecurity: LUA compiled version="Lua 5.1" [Fri May 25 19:53:11 2012] [notice] ModSecurity: LIBXML compiled version="2.7.8" [Fri May 25 19:53:12 2012] [notice] Apache/2.2.22 (Ubuntu) PHP/5.3.8-ZS5.5.0 configured -- resuming normal operations and here is my httpd.conf: # Name based virtual hosting <virtualhost *:80> ServerName www-redirect KeepAlive Off RewriteEngine On RewriteCond %{HTTP_HOST} ^[^\./]+\.[^\./]+$ RewriteRule ^/(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L] </virtualhost> Alias /shared/js "/home/web/library/js" Alias /shared/image "/home/web/library/image" <IfModule mod_expires.c> <FilesMatch "\.(jpe?g|png|gif|js|css|doc|rtf|xls|pdf)$"> ExpiresActive On ExpiresDefault "access plus 1 week" </FilesMatch> </IfModule> ErrorLog ${APACHE_LOG_DIR}/error.log LogLevel warn <Directory /> Options FollowSymLinks AllowOverride None Order allow,deny allow from all </Directory> <Location /> RewriteEngine On RewriteCond %{REQUEST_FILENAME} -s [OR] RewriteCond %{REQUEST_FILENAME} -l [OR] RewriteCond %{REQUEST_FILENAME} -d RewriteRule ^.*$ - [NC,L] RewriteRule ^.*$ /index.php [NC,L] </Location> netstat -tap gives: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 *:mysql *:* LISTEN 765/mysqld tcp 0 0 *:pop3 *:* LISTEN 744/dovecot tcp 0 0 *:imap2 *:* LISTEN 744/dovecot tcp 0 0 *:http *:* LISTEN 19861/apache2 tcp 0 0 *:smtp *:* LISTEN 30365/master tcp 0 0 *:4444 *:* LISTEN 634/sshd tcp 0 0 *:kamanda *:* LISTEN 1167/lighttpd tcp 0 0 *:imaps *:* LISTEN 744/dovecot tcp 0 0 *:amandaidx *:* LISTEN 1167/lighttpd tcp 0 0 localhost.loc:amidxtape *:* LISTEN 19861/apache2 tcp 0 0 *:pop3s *:* LISTEN 744/dovecot tcp 0 384 mail.mysite.:4444 231.214.14.37.dyn:41909 ESTABLISHED 19039/sshd: web [pr tcp 0 0 localhost.localdo:mysql localhost.localdo:48252 ESTABLISHED 765/mysqld tcp 0 0 mail.mysite.:http 231.214.14.37.dyn:54686 TIME_WAIT - tcp 0 0 mail.mysite.:4444 231.214.14.37.dyn:42419 ESTABLISHED 19372/sshd: web [pr tcp 0 0 localhost.localdo:48252 localhost.localdo:mysql ESTABLISHED 19884/auth tcp 0 0 mail.mysite.:http 231.214.14.37.dyn:54685 TIME_WAIT - tcp6 0 0 [::]:pop3 [::]:* LISTEN 744/dovecot tcp6 0 0 [::]:imap2 [::]:* LISTEN 744/dovecot tcp6 0 0 [::]:smtp [::]:* LISTEN 30365/master tcp6 0 0 [::]:4444 [::]:* LISTEN 634/sshd tcp6 0 0 [::]:imaps [::]:* LISTEN 744/dovecot tcp6 0 0 [::]:pop3s [::]:* LISTEN 744/dovecot Anyone knows what I am doing wrong? Perhaps I should take some additional steps to make apache listen 0n 443 but that it stops listening on 80 altogether I can't understand.

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• regarding the Windows Phone 7 series, XNA and Visual Basic

  - by Chris Williams

  as long as we're talking about VB... I figured I would share this as well. Hi everyone, I'm about to express a sentiment that might ruffle a few feathers, but I think most of you know me well enough to know I love like accept VB for what it is and that what I'm about to say is with good intentions. (The rest of you, who don't know me, please take my word for it.) The world is full of VB developers, I was one of them for a long time. I think it's safe to assume that none of us are ignorant people who require handholding. We're working professionals, making a living by using our skills as developers. I'm also willing to bet that quite a few of us are fluent in C# as well as VB. It may not be your preferred language, but many of you can do it and you prove that nearly every day. Honestly, I don't know ANY developers or consultants that have only known ONE language ever. So it pains me greatly when I see the word "CAN'T" being tossed around like a crutch... as in "we CAN'T develop for the windows phone or we CAN'T develop XNA games." At MIX, Microsoft hath decreed that C# is the language of choice for developing for the Windows Phone 7. I think it's a safe bet that you won't see VB support if it isn't there already. (Just like XNA... which is up to version 4.0 by now.)  So what? (Yeah... I said it.) I think everyone here can agree that actual coding is only one part of software design and development. There is nothing stopping ANY of you from beginning the process of designing your killer phone app, writing up specs, requirements, doing UI design, workflow, mockups, storyboards, art, etc.... None of these things are language dependent. IF by the time you've got that stuff out of the way, and there's still no VB support, then start doing some rapid prototyping of your app in C# (I know, I know... heresy!)  You still have to spend time learning how the phone does things, what UI tricks do what, what paradigms make sense, how to use to accelerometer and the tilt and the multitouch functionality. I can guarantee you that time spent doing this is a great investment, no matter WHAT extension your code files have. Eventually, you may have a working prototype. IF by this time, there's STILL no VB support... fret not, you've made significant progress on your app. You've designed it, prototyped it, figured out how to use the phone specific features... so you might as well finish it and pat yourself on the back for learning something new... and possibly being first to market with your new app. I'll be happy to argue any and all of these points online or off with anyone who cares to do so, but there is one undeniable point that you simply can't argue:  Your potential customers do not care AT ALL what programming language you used to write the app they are about to purchase. They care that it works. If your biggest concern is being first to market, than stop complaining and get busy because you're running out of time and the 3000+ people who were at MIX certainly aren't waiting for you. They've already started working on their apps.

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• Set up lnux box for hosting a-z

  - by microchasm

  I am in the process of reinstalling the OS on a machine that will be used to host a couple of apps for our business. The apps will be local only; access from external clients will be via vpn only. The prior setup used a hosting control panel (Plesk) for most of the admin, and I was looking at using another similar piece of software for the reinstall - but I figured I should finally learn how it all works. I can do most of the things the software would do for me, but am unclear on the symbiosis of it all. This is all an attempt to further distance myself from the land of Configuration Programmer/Programmer, if at all possible. I can't find a full walkthrough anywhere for what I'm looking for, so I thought I'd put up this question, and if people can help me on the way I will edit this with the answers, and document my progress/pitfalls. Hopefully someday this will help someone down the line. The details: CentOS 5.5 x86_64 httpd: Apache/2.2.3 mysql: 5.0.77 (to be upgraded) php: 5.1 (to be upgraded) The requirements: SECURITY!! Secure file transfer Secure client access (SSL Certs and CA) Secure data storage Virtualhosts/multiple subdomains Local email would be nice, but not critical The Steps: Download latest CentOS DVD-iso (torrent worked great for me). Install CentOS: While going through the install, I checked the Server Components option thinking I was going to be using another Plesk-like admin. In hindsight, considering I've decided to try to go my own way, this probably wasn't the best idea. Basic config: Setup users, networking/ip address etc. Yum update/upgrade. Upgrade PHP: To upgrade PHP to the latest version, I had to look to another repo outside CentOS. IUS looks great and I'm happy I found it! cd /tmp #wget http://dl.iuscommunity.org/pub/ius/stable/Redhat/5/x86_64/epel-release-1-1.ius.el5.noarch.rpm #rpm -Uvh epel-release-1-1.ius.el5.noarch.rpm #wget http://dl.iuscommunity.org/pub/ius/stable/Redhat/5/x86_64/ius-release-1-4.ius.el5.noarch.rpm #rpm -Uvh ius-release-1-4.ius.el5.noarch.rpm yum list | grep -w \.ius\. [will list all packages available in the IUS repo] rpm -qa | grep php [will list installed packages needed to be removed. the installed packages need to be removed before you can install the IUS packages otherwise there will be conflicts] #yum shell >remove php-gd php-cli php-odbc php-mbstring php-pdo php php-xml php-common php-ldap php-mysql php-imap Setting up Remove Process >install php53 php53-mcrypt php53-mysql php53-cli php53-common php53-ldap php53-imap php53-devel >transaction solve >transaction run Leaving Shell #php -v PHP 5.3.2 (cli) (built: Apr 6 2010 18:13:45) This process removes the old version of PHP and installs the latest. To upgrade mysql: Pretty much the same process as above with PHP #/etc/init.d/mysqld stop [OK] rpm -qa | grep mysql [installed mysql packages] #yum shell >remove mysql mysql-server Setting up Remove Process >install mysql51 mysql51-server mysql51-devel >transaction solve >transaction run Leaving Shell #service mysqld start [OK] #mysql -v Server version: 5.1.42-ius Distributed by The IUS Community Project The above upgrade instructions courtesy of IUS wiki: http://wiki.iuscommunity.org/Doc/ClientUsageGuide Create a chroot jail to hold sftp user via rssh. This will force SCP/SFTP and will circumvent traditional FTP server setup. #cd /tmp #wget http://dag.wieers.com/rpm/packages/rssh/rssh-2.3.2-1.2.el5.rf.x86_64.rpm #rpm -ivh rssh-2.3.2-1.2.el5.rf.x86_64.rpm #useradd -m -d /home/dev -s /usr/bin/rssh dev #passwd dev Edit /etc/rssh.conf to grant access to SFTP to rssh users. #vi /etc/rssh.conf Uncomment line allowscp This allows me to connect to the machine via SFTP protocol in Transmit (my FTP program of choice; I'm sure it's similar with other FTP apps). Above instructions for SFTP appropriated (with appreciation!) from http://www.cyberciti.biz/tips/linux-unix-restrict-shell-access-with-rssh.html And this is where I'm at. I will keep editing this as I make progress. Any tips on how to Configure virtual interfaces/ip based virtual hosts for SSL, setting up a CA, or anything else would be appreciated.

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• Oracle Employees Support New World Record for IYF Children's Hour

  - by Maria Sandu

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 960 students ‘crouched’, ‘touched’ and ‘set’ under the watchful eye of International Rugby Referee Alain Roland, and supported by Oracle employees, to successfully set a new world record for the World’s Largest Scrum to raise funds and awareness for the Irish Youth Foundation. Last year Oracle Employees supported the Irish Youth Foundation by donating funds from their payroll through the Giving Tree Appeal. We were the largest corporate donor to the IYF by raising €3075. To acknowledge our generosity the IYF asked Oracle Leadership in Society team members to participate in their most recent campaign which was to break the Guinness Book of Records by forming the World’s Largest Rugby Scrum. This was a wonderful opportunity for Oracle’s Leadership in Society to promote the charity, support education and to make a mark in the Corporate Social Responsibility field. The students who formed the scrum also gave up their lunch money and raised a total of €3000. This year we hope Oracle Employees will once again support the IYF with the challenge to match that amount. On the 24th of October the sun shone down on the streaming lines of students entering the field. 480 students were decked out in bright red Oracle T-Shirts against the other 480 in blue and white jerseys - all ready to form a striking scrum. Ryan Tubridy the host of the event made the opening announcement and with the blow of a whistle the Scum began. 960 students locked tight together with the Leinster players also at each side. Leinster Manager Matt O’Connor was there along with presenters Ryan Tubridy and George Hook to assist with getting the boys in line and keeping the shape of the scrum. In accordance with Guinness Book of Records rules, the ball was fed into the scrum properly by Ireland and Leinster scrum-half, Eoin Reddan, and was then passed out the line to his Leinster team mates including Ian Madigan, Brendan Macken and Jordi Murphy, also proudly sporting the Oracle T-Shirt. The new World Record was made, everyone gave a big cheer and thankfully nobody got injured! Thank you to everyone in Oracle who donated last year through the Giving Tree Appeal. Your generosity has gone a long way to support local groups both. Last year’s donation was so substantial that the IYF were able to spread it across two youth groups: The first being Ballybough Youth Project in Dublin. The funding gave them the chance to give 24 young people from their project the chance to get away from the inner city and the problems and issues they face in their daily life by taking a trip to the Cavan Centre to spend a weekend away in a safe and comfortable environment; a very rare holiday in these young people’s lives. The Rahoon Family Centre. Used the money to help secure the long term sustainability of their project. They act as an educational/social/fun project that has been working with disadvantaged children for the past 16 years. Their aim is to change young people’s future with fun /social education and supporting them so they can maximize their creativity and potential. We hope you can help support this worthy cause again this year, so keep an eye out for the Children’s Hour and Giving Tree Appeal! About the Irish Youth Foundation The IYF provides opportunities for marginalised children and young people facing difficult and extreme conditions to experience success in their lives. It passionately believes that achievement starts with opportunity. The IYF’s strategy is based on providing safe places where children can go after school; to grow, to learn and to play; and providing opportunities for teenagers from under-served communities to succeed and excel in their lives. The IYF supports innovative grassroots projects operated by dedicated professionals who understand young people and care about them. This allows the IYF to focus on supporting young people at risk of dropping out of school and, in particular, on the critical transition from primary to secondary school; and empowering teenagers from disadvantaged neighborhoods to become engaged in their local communities. Find out more here www.iyf.ie

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• Severe mysqldump performance degradation using Centos Linux, 8GB PAE and MySQL 5.0.77

  - by Duncan Harris

  We use MySQL 5.0.77 on CentOS 5.5 on VMWare: Linux dev.ic.soschildrensvillages.org.uk 2.6.18-194.11.4.el5PAE #1 SMP Tue Sep 21 05:48:23 EDT 2010 i686 i686 i386 GNU/Linux We have recently upgraded from 4GB RAM to 8GB. When we did this the time of our mysqldump overnight backup jumped from under 10 minutes to over 2 hours. It also caused unresponsiveness on our plone based web site due to database load. The dump is using the optimized mysqldump format and is spooled directly through a socket to another server. Any ideas on what we could do to fix gratefully appreciated. Would a MySQL upgrade help? Anything we can do to MySQL config? Anything we can do to Linux config? Or do we have to add another server or go to 64-bit? We ran a previous (non-virtual) server on 6GB PAE and didn't notice a similar issue. This was on same MySQL version, but Centos 4.4. Server config file: [mysqld] port=3307 socket=/tmp/mysql_live.sock wait_timeout=31536000 interactive_timeout=31536000 datadir=/var/mysql/live/data user=mysql max_connections = 200 max_allowed_packet = 64M table_cache = 2048 binlog_cache_size = 128K max_heap_table_size = 32M sort_buffer_size = 2M join_buffer_size = 2M lower_case_table_names = 1 innodb_data_file_path = ibdata1:10M:autoextend innodb_buffer_pool_size=1G innodb_log_file_size=300M innodb_log_buffer_size=8M innodb_flush_log_at_trx_commit=1 innodb_file_per_table [mysqldump] # Do not buffer the whole result set in memory before writing it to # file. Required for dumping very large tables quick max_allowed_packet = 64M [mysqld_safe] # Increase the amount of open files allowed per process. Warning: Make # sure you have set the global system limit high enough! The high value # is required for a large number of opened tables open-files-limit = 8192 Server variables: mysql> show variables; +---------------------------------+------------------------------------------------------------------+ | Variable_name | Value | +---------------------------------+------------------------------------------------------------------+ | auto_increment_increment | 1 | | auto_increment_offset | 1 | | automatic_sp_privileges | ON | | back_log | 50 | | basedir | /usr/local/mysql-5.0.77-linux-i686-glibc23/ | | binlog_cache_size | 131072 | | bulk_insert_buffer_size | 8388608 | | character_set_client | latin1 | | character_set_connection | latin1 | | character_set_database | latin1 | | character_set_filesystem | binary | | character_set_results | latin1 | | character_set_server | latin1 | | character_set_system | utf8 | | character_sets_dir | /usr/local/mysql-5.0.77-linux-i686-glibc23/share/mysql/charsets/ | | collation_connection | latin1_swedish_ci | | collation_database | latin1_swedish_ci | | collation_server | latin1_swedish_ci | | completion_type | 0 | | concurrent_insert | 1 | | connect_timeout | 10 | | datadir | /var/mysql/live/data/ | | date_format | %Y-%m-%d | | datetime_format | %Y-%m-%d %H:%i:%s | | default_week_format | 0 | | delay_key_write | ON | | delayed_insert_limit | 100 | | delayed_insert_timeout | 300 | | delayed_queue_size | 1000 | | div_precision_increment | 4 | | keep_files_on_create | OFF | | engine_condition_pushdown | OFF | | expire_logs_days | 0 | | flush | OFF | | flush_time | 0 | | ft_boolean_syntax | + -><()~*:""&| | | ft_max_word_len | 84 | | ft_min_word_len | 4 | | ft_query_expansion_limit | 20 | | ft_stopword_file | (built-in) | | group_concat_max_len | 1024 | | have_archive | YES | | have_bdb | NO | | have_blackhole_engine | YES | | have_compress | YES | | have_crypt | YES | | have_csv | YES | | have_dynamic_loading | YES | | have_example_engine | NO | | have_federated_engine | YES | | have_geometry | YES | | have_innodb | YES | | have_isam | NO | | have_merge_engine | YES | | have_ndbcluster | DISABLED | | have_openssl | DISABLED | | have_ssl | DISABLED | | have_query_cache | YES | | have_raid | NO | | have_rtree_keys | YES | | have_symlink | YES | | hostname | app.ic.soschildrensvillages.org.uk | | init_connect | | | init_file | | | init_slave | | | innodb_additional_mem_pool_size | 1048576 | | innodb_autoextend_increment | 8 | | innodb_buffer_pool_awe_mem_mb | 0 | | innodb_buffer_pool_size | 1073741824 | | innodb_checksums | ON | | innodb_commit_concurrency | 0 | | innodb_concurrency_tickets | 500 | | innodb_data_file_path | ibdata1:10M:autoextend | | innodb_data_home_dir | | | innodb_adaptive_hash_index | ON | | innodb_doublewrite | ON | | innodb_fast_shutdown | 1 | | innodb_file_io_threads | 4 | | innodb_file_per_table | ON | | innodb_flush_log_at_trx_commit | 1 | | innodb_flush_method | | | innodb_force_recovery | 0 | | innodb_lock_wait_timeout | 50 | | innodb_locks_unsafe_for_binlog | OFF | | innodb_log_arch_dir | | | innodb_log_archive | OFF | | innodb_log_buffer_size | 8388608 | | innodb_log_file_size | 314572800 | | innodb_log_files_in_group | 2 | | innodb_log_group_home_dir | ./ | | innodb_max_dirty_pages_pct | 90 | | innodb_max_purge_lag | 0 | | innodb_mirrored_log_groups | 1 | | innodb_open_files | 300 | | innodb_rollback_on_timeout | OFF | | innodb_support_xa | ON | | innodb_sync_spin_loops | 20 | | innodb_table_locks | ON | | innodb_thread_concurrency | 8 | | innodb_thread_sleep_delay | 10000 | | interactive_timeout | 31536000 | | join_buffer_size | 2097152 | | key_buffer_size | 8384512 | | key_cache_age_threshold | 300 | | key_cache_block_size | 1024 | | key_cache_division_limit | 100 | | language | /usr/local/mysql-5.0.77-linux-i686-glibc23/share/mysql/english/ | | large_files_support | ON | | large_page_size | 0 | | large_pages | OFF | | lc_time_names | en_US | | license | GPL | | local_infile | ON | | locked_in_memory | OFF | | log | OFF | | log_bin | OFF | | log_bin_trust_function_creators | OFF | | log_error | | | log_queries_not_using_indexes | OFF | | log_slave_updates | OFF | | log_slow_queries | OFF | | log_warnings | 1 | | long_query_time | 10 | | low_priority_updates | OFF | | lower_case_file_system | OFF | | lower_case_table_names | 1 | | max_allowed_packet | 67108864 | | max_binlog_cache_size | 4294963200 | | max_binlog_size | 1073741824 | | max_connect_errors | 10 | | max_connections | 200 | | max_delayed_threads | 20 | | max_error_count | 64 | | max_heap_table_size | 33554432 | | max_insert_delayed_threads | 20 | | max_join_size | 18446744073709551615 | | max_length_for_sort_data | 1024 | | max_prepared_stmt_count | 16382 | | max_relay_log_size | 0 | | max_seeks_for_key | 4294967295 | | max_sort_length | 1024 | | max_sp_recursion_depth | 0 | | max_tmp_tables | 32 | | max_user_connections | 0 | | max_write_lock_count | 4294967295 | | multi_range_count | 256 | | myisam_data_pointer_size | 6 | | myisam_max_sort_file_size | 2146435072 | | myisam_recover_options | OFF | | myisam_repair_threads | 1 | | myisam_sort_buffer_size | 8388608 | | myisam_stats_method | nulls_unequal | | ndb_autoincrement_prefetch_sz | 1 | | ndb_force_send | ON | | ndb_use_exact_count | ON | | ndb_use_transactions | ON | | ndb_cache_check_time | 0 | | ndb_connectstring | | | net_buffer_length | 16384 | | net_read_timeout | 30 | | net_retry_count | 10 | | net_write_timeout | 60 | | new | OFF | | old_passwords | OFF | | open_files_limit | 8192 | | optimizer_prune_level | 1 | | optimizer_search_depth | 62 | | pid_file | /var/mysql/live/mysqld.pid | | plugin_dir | | | port | 3307 | | preload_buffer_size | 32768 | | profiling | OFF | | profiling_history_size | 15 | | protocol_version | 10 | | query_alloc_block_size | 8192 | | query_cache_limit | 1048576 | | query_cache_min_res_unit | 4096 | | query_cache_size | 0 | | query_cache_type | ON | | query_cache_wlock_invalidate | OFF | | query_prealloc_size | 8192 | | range_alloc_block_size | 4096 | | read_buffer_size | 131072 | | read_only | OFF | | read_rnd_buffer_size | 262144 | | relay_log | | | relay_log_index | | | relay_log_info_file | relay-log.info | | relay_log_purge | ON | | relay_log_space_limit | 0 | | rpl_recovery_rank | 0 | | secure_auth | OFF | | secure_file_priv | | | server_id | 0 | | skip_external_locking | ON | | skip_networking | OFF | | skip_show_database | OFF | | slave_compressed_protocol | OFF | | slave_load_tmpdir | /tmp/ | | slave_net_timeout | 3600 | | slave_skip_errors | OFF | | slave_transaction_retries | 10 | | slow_launch_time | 2 | | socket | /tmp/mysql_live.sock | | sort_buffer_size | 2097152 | | sql_big_selects | ON | | sql_mode | | | sql_notes | ON | | sql_warnings | OFF | | ssl_ca | | | ssl_capath | | | ssl_cert | | | ssl_cipher | | | ssl_key | | | storage_engine | MyISAM | | sync_binlog | 0 | | sync_frm | ON | | system_time_zone | GMT | | table_cache | 2048 | | table_lock_wait_timeout | 50 | | table_type | MyISAM | | thread_cache_size | 0 | | thread_stack | 196608 | | time_format | %H:%i:%s | | time_zone | SYSTEM | | timed_mutexes | OFF | | tmp_table_size | 33554432 | | tmpdir | /tmp/ | | transaction_alloc_block_size | 8192 | | transaction_prealloc_size | 4096 | | tx_isolation | REPEATABLE-READ | | updatable_views_with_limit | YES | | version | 5.0.77 | | version_comment | MySQL Community Server (GPL) | | version_compile_machine | i686 | | version_compile_os | pc-linux-gnu | | wait_timeout | 31536000 | +---------------------------------+------------------------------------------------------------------+ 237 rows in set (0.00 sec)

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• CPU Utilization LAMP stack

  - by Max

  We've got an ec2 m2.4xlarge running Magento (centos 5.6, httpd 2.2, php 5.2.17 with eaccelerator 0.9.5.3, mysql 5.1.52). Right now we're getting a large traffic spike, and our top looks like this: top - 09:41:29 up 31 days, 1:12, 1 user, load average: 120.01, 129.03, 113.23 Tasks: 1190 total, 18 running, 1172 sleeping, 0 stopped, 0 zombie Cpu(s): 97.3%us, 1.8%sy, 0.0%ni, 0.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.4%st Mem: 71687720k total, 36898928k used, 34788792k free, 49692k buffers Swap: 880737784k total, 0k used, 880737784k free, 1586524k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2433 mysql 15 0 23.6g 4.5g 7112 S 564.7 6.6 33607:34 mysqld 24046 apache 16 0 411m 65m 28m S 26.4 0.1 0:09.05 httpd 24360 apache 15 0 410m 60m 25m S 26.4 0.1 0:03.65 httpd 24993 apache 16 0 410m 57m 21m S 26.1 0.1 0:01.41 httpd 24838 apache 16 0 428m 74m 20m S 24.8 0.1 0:02.37 httpd 24359 apache 16 0 411m 62m 26m R 22.3 0.1 0:08.12 httpd 23850 apache 15 0 411m 64m 27m S 16.8 0.1 0:14.54 httpd 25229 apache 16 0 404m 46m 17m R 10.2 0.1 0:00.71 httpd 14594 apache 15 0 404m 63m 34m S 8.4 0.1 1:10.26 httpd 24955 apache 16 0 404m 50m 21m R 8.4 0.1 0:01.66 httpd 24313 apache 16 0 399m 46m 22m R 8.1 0.1 0:02.30 httpd 25119 apache 16 0 411m 59m 23m S 6.8 0.1 0:01.45 httpd Questions: Would giving msyqld more memory help it cache queries and react faster? If so, how? Other than splitting mysql and php to separate servers (which we're about to do) is there anything else we could/should be doing? Thanks! UPDATE: Here's our my.cnf along with the output of mysqltuner. It looks like a cache problem. Thanks again! # cat /etc/my.cnf [client] port = **** socket = /var/lib/mysql/mysql.sock [mysqld] datadir=/mnt/persistent/mysql port=**** socket=/var/lib/mysql/mysql.sock key_buffer = 512M max_allowed_packet = 64M table_cache = 1024 sort_buffer_size = 8M read_buffer_size = 4M read_rnd_buffer_size = 2M myisam_sort_buffer_size = 64M thread_cache_size = 128M tmp_table_size = 128M join_buffer_size = 1M query_cache_limit = 2M query_cache_size= 64M query_cache_type = 1 max_connections = 1000 thread_stack = 128K thread_concurrency = 48 log-bin=mysql-bin server-id = 1 wait_timeout = 300 innodb_data_home_dir = /mnt/persistent/mysql/ innodb_data_file_path = ibdata1:10M:autoextend innodb_buffer_pool_size = 20G innodb_additional_mem_pool_size = 20M innodb_log_file_size = 64M innodb_log_buffer_size = 8M innodb_flush_log_at_trx_commit = 1 innodb_lock_wait_timeout = 50 innodb_thread_concurrency = 48 ft_min_word_len=3 [myisamchk] ft_min_word_len=3 key_buffer = 128M sort_buffer_size = 128M read_buffer = 2M write_buffer = 2M # ./mysqltuner.pl >> MySQLTuner 1.2.0 - Major Hayden <[email protected]> >> Bug reports, feature requests, and downloads at http://mysqltuner.com/ >> Run with '--help' for additional options and output filtering -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.1.52-log [OK] Operating on 64-bit architecture -------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB +Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 2G (Tables: 26) [--] Data in InnoDB tables: 749M (Tables: 250) [!!] Total fragmented tables: 262 -------- Security Recommendations ------------------------------------------- -------- Performance Metrics ------------------------------------------------- [--] Up for: 31d 2h 30m 38s (680M q [253.371 qps], 2M conn, TX: 4825B, RX: 236B) [--] Reads / Writes: 89% / 11% [--] Total buffers: 20.6G global + 15.1M per thread (1000 max threads) [OK] Maximum possible memory usage: 35.4G (51% of installed RAM) [OK] Slow queries: 0% (35K/680M) [OK] Highest usage of available connections: 53% (537/1000) [OK] Key buffer size / total MyISAM indexes: 512.0M/457.2M [OK] Key buffer hit rate: 100.0% (9B cached / 264K reads) [OK] Query cache efficiency: 42.3% (260M cached / 615M selects) [!!] Query cache prunes per day: 4384652 [OK] Sorts requiring temporary tables: 0% (1K temp sorts / 38M sorts) [!!] Joins performed without indexes: 100404 [OK] Temporary tables created on disk: 17% (7M on disk / 45M total) [OK] Thread cache hit rate: 99% (537 created / 2M connections) [!!] Table cache hit rate: 0% (1K open / 946K opened) [OK] Open file limit used: 9% (453/5K) [OK] Table locks acquired immediately: 99% (758M immediate / 758M locks) [OK] InnoDB data size / buffer pool: 749.3M/20.0G -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance Enable the slow query log to troubleshoot bad queries Adjust your join queries to always utilize indexes Increase table_cache gradually to avoid file descriptor limits Variables to adjust: query_cache_size (> 64M) join_buffer_size (> 1.0M, or always use indexes with joins) table_cache (> 1024)

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• Feynman's inbox

  - by user12607414

  Here is Richard Feynman writing on the ease of criticizing theories, and the difficulty of forming them: The problem is not just to say something might be wrong, but to replace it by something — and that is not so easy. As soon as any really definite idea is substituted it becomes almost immediately apparent that it does not work. The second difficulty is that there is an infinite number of possibilities of these simple types. It is something like this. You are sitting working very hard, you have worked for a long time trying to open a safe. Then some Joe comes along who knows nothing about what you are doing, except that you are trying to open the safe. He says ‘Why don’t you try the combination 10:20:30?’ Because you are busy, you have tried a lot of things, maybe you have already tried 10:20:30. Maybe you know already that the middle number is 32 not 20. Maybe you know as a matter of fact that it is a five digit combination… So please do not send me any letters trying to tell me how the thing is going to work. I read them — I always read them to make sure that I have not already thought of what is suggested — but it takes too long to answer them, because they are usually in the class ‘try 10:20:30’. (“Seeking New Laws”, page 161 in The Character of Physical Law.) As a sometime designer (and longtime critic) of widely used computer systems, I have seen similar difficulties appear when anyone undertakes to publicly design a piece of software that may be used by many thousands of customers. (I have been on both sides of the fence, of course.) The design possibilities are endless, but the deep design problems are usually hidden beneath a mass of superfluous detail. The sheer numbers can be daunting. Even if only one customer out of a thousand feels a need to express a passionately held idea, it can take a long time to read all the mail. And it is a fact of life that many of those strong suggestions are only weakly supported by reason or evidence. Opinions are plentiful, but substantive research is time-consuming, and hence rare. A related phenomenon commonly seen with software is bike-shedding, where interlocutors focus on surface details like naming and syntax… or (come to think of it) like lock combinations. On the other hand, software is easier than quantum physics, and the population of people able to make substantial suggestions about software systems is several orders of magnitude bigger than Feynman’s circle of colleagues. My own work would be poorer without contributions — sometimes unsolicited, sometimes passionately urged on me — from the open source community. If a Nobel prize winner thought it was worthwhile to read his mail on the faint chance of learning a good idea, I am certainly not going to throw mine away. (In case anyone is still reading this, and is wondering what provoked a meditation on the quality of one’s inbox contents, I’ll simply point out that the volume has been very high, for many months, on the Lambda-Dev mailing list, where the next version of the Java language is being discussed. Bravo to those of my colleagues who are surfing that wave.) I started this note thinking there was an odd parallel between the life of the physicist and that of a software designer. On second thought, I’ll bet that is the story for anybody who works in public on something requiring special training. (And that would be pretty much anything worth doing.) In any case, Feynman saw it clearly and said it well.

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• RemoveHandler Issues with Custom Events

  - by Jeff Certain

  This is a case of things being more complicated that I thought they should be. Since it took a while to figure this one out, I thought it was worth explaining and putting all of the pieces to the answer in one spot. Let me set the stage. Architecturally, I have the notion of generic producers and consumers. These put items onto, and remove items from, a queue. This provides a generic, thread-safe mechanism to load balance the creation and processing of work items in our application. Part of the IProducer(Of T) interface is: 1: Public Interface IProducer(Of T) 2: Event ItemProduced(ByVal sender As IProducer(Of T), ByVal item As T) 3: Event ProductionComplete(ByVal sender As IProducer(Of T)) 4: End Interface Nothing sinister there, is there? In order to simplify our developers’ lives, I wrapped the queue with some functionality to manage the produces and consumers. Since the developer can specify the number of producers and consumers that are spun up, the queue code manages adding event handlers as the producers and consumers are instantiated. Now, we’ve been having some memory leaks and, in order to eliminate the possibility that this was caused by weak references to event handles, I wanted to remove them. This is where it got dicey. My first attempt looked like this: 1: For Each producer As P In Producers 2: RemoveHandler producer.ItemProduced, AddressOf ItemProducedHandler 3: RemoveHandler producer.ProductionComplete, AddressOf ProductionCompleteHandler 4: producer.Dispose() 5: Next What you can’t see in my posted code are the warnings this caused. The 'AddressOf' expression has no effect in this context because the method argument to 'AddressOf' requires a relaxed conversion to the delegate type of the event. Assign the 'AddressOf' expression to a variable, and use the variable to add or remove the method as the handler.  Now, what on earth does that mean? Well, a quick Bing search uncovered a whole bunch of talk about delegates. The first solution I found just changed all parameters in the event handler to Object. Sorry, but no. I used generics precisely because I wanted type safety, not because I wanted to use Object. More searching. Eventually, I found this forum post, where Jeff Shan revealed a missing piece of the puzzle. The other revelation came from Lian_ZA in this post. However, these two only hinted at the solution. Trying some of what they suggested led to finally getting an invalid cast exception that revealed the existence of ItemProducedEventHandler. Hold on a minute! I didn’t create that delegate. There’s nothing even close to that name in my code… except the ItemProduced event in the interface. Could it be? Naaaaah. Hmmm…. Well, as it turns out, there is a delegate created by the compiler for each event. By explicitly creating a delegate that refers to the method in question, implicitly cast to the generated delegate type, I was able to remove the handlers: 1: For Each producer As P In Producers 2: Dim _itemProducedHandler As IProducer(Of T).ItemProducedEventHandler = AddressOf ItemProducedHandler 3: RemoveHandler producer.ItemProduced, _itemProducedHandler 4:  5: Dim _productionCompleteHandler As IProducer(Of T).ProductionCompleteEventHandler = AddressOf ProductionCompleteHandler 6: RemoveHandler producer.ProductionComplete, _productionCompleteHandler 7: producer.Dispose() 8: Next That’s “all” it took to finally be able to remove the event handlers and maintain type-safe code. Hopefully, this will save you the same challenges I had in trying to figure out how to fix this issue!

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• ConcurrentDictionary<TKey,TValue> used with Lazy<T>

  - by Reed

  In a recent thread on the MSDN forum for the TPL, Stephen Toub suggested mixing ConcurrentDictionary<T,U> with Lazy<T>.  This provides a fantastic model for creating a thread safe dictionary of values where the construction of the value type is expensive.  This is an incredibly useful pattern for many operations, such as value caches. The ConcurrentDictionary<TKey, TValue> class was added in .NET 4, and provides a thread-safe, lock free collection of key value pairs.  While this is a fantastic replacement for Dictionary<TKey, TValue>, it has a potential flaw when used with values where construction of the value class is expensive. The typical way this is used is to call a method such as GetOrAdd to fetch or add a value to the dictionary.  It handles all of the thread safety for you, but as a result, if two threads call this simultaneously, two instances of TValue can easily be constructed. If TValue is very expensive to construct, or worse, has side effects if constructed too often, this is less than desirable.  While you can easily work around this with locking, Stephen Toub provided a very clever alternative – using Lazy<TValue> as the value in the dictionary instead. This looks like the following.  Instead of calling: MyValue value = dictionary.GetOrAdd( key, () => new MyValue(key)); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } We would instead use a ConcurrentDictionary<TKey, Lazy<TValue>>, and write: MyValue value = dictionary.GetOrAdd( key, () => new Lazy<MyValue>( () => new MyValue(key))) .Value; This simple change dramatically changes how the operation works.  Now, if two threads call this simultaneously, instead of constructing two MyValue instances, we construct two Lazy<MyValue> instances. However, the Lazy<T> class is very cheap to construct.  Unlike “MyValue”, we can safely afford to construct this twice and “throw away” one of the instances. We then call Lazy<T>.Value at the end to fetch our “MyValue” instance.  At this point, GetOrAdd will always return the same instance of Lazy<MyValue>.  Since Lazy<T> doesn’t construct the MyValue instance until requested, the actual MyClass instance returned is only constructed once.

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• Set up lnux box for hosting a-z [apache mysql php ssl]

  - by microchasm

  I am in the process of reinstalling the OS on a machine that will be used to host a couple of apps for our business. The apps will be local only; access from external clients will be via vpn only. The prior setup used a hosting control panel (Plesk) for most of the admin, and I was looking at using another similar piece of software for the reinstall - but I figured I should finally learn how it all works. I can do most of the things the software would do for me, but am unclear on the symbiosis of it all. This is all an attempt to further distance myself from the land of Configuration Programmer/Programmer, if at all possible. I can't find a full walkthrough anywhere for what I'm looking for, so I thought I'd put up this question, and if people can help me on the way I will edit this with the answers, and document my progress/pitfalls. Hopefully someday this will help someone down the line. The details: CentOS 5.5 x86_64 httpd: Apache/2.2.3 mysql: 5.0.77 (to be upgraded) php: 5.1 (to be upgraded) The requirements: SECURITY!! Secure file transfer Secure client access (SSL Certs and CA) Secure data storage Virtualhosts/multiple subdomains Local email would be nice, but not critical The Steps: Download latest CentOS DVD-iso (torrent worked great for me). Install CentOS: While going through the install, I checked the Server Components option thinking I was going to be using another Plesk-like admin. In hindsight, considering I've decided to try to go my own way, this probably wasn't the best idea. Basic config: Setup users, networking/ip address etc. Yum update/upgrade. Upgrade PHP: To upgrade PHP to the latest version, I had to look to another repo outside CentOS. IUS looks great and I'm happy I found it! cd /tmp #wget http://dl.iuscommunity.org/pub/ius/stable/Redhat/5/x86_64/epel-release-1-1.ius.el5.noarch.rpm #rpm -Uvh epel-release-1-1.ius.el5.noarch.rpm #wget http://dl.iuscommunity.org/pub/ius/stable/Redhat/5/x86_64/ius-release-1-4.ius.el5.noarch.rpm #rpm -Uvh ius-release-1-4.ius.el5.noarch.rpm yum list | grep -w \.ius\. [will list all packages available in the IUS repo] rpm -qa | grep php [will list installed packages needed to be removed. the installed packages need to be removed before you can install the IUS packages otherwise there will be conflicts] #yum shell >remove php-gd php-cli php-odbc php-mbstring php-pdo php php-xml php-common php-ldap php-mysql php-imap Setting up Remove Process >install php53 php53-mcrypt php53-mysql php53-cli php53-common php53-ldap php53-imap php53-devel >transaction solve >transaction run Leaving Shell #php -v PHP 5.3.2 (cli) (built: Apr 6 2010 18:13:45) This process removes the old version of PHP and installs the latest. To upgrade mysql: Pretty much the same process as above with PHP #/etc/init.d/mysqld stop [OK] rpm -qa | grep mysql [installed mysql packages] #yum shell >remove mysql mysql-server Setting up Remove Process >install mysql51 mysql51-server mysql51-devel >transaction solve >transaction run Leaving Shell #service mysqld start [OK] #mysql -v Server version: 5.1.42-ius Distributed by The IUS Community Project And this is where I'm at. I will keep editing this as I make progress. Any tips on how to Configure Virtualhosts for SSL, setting up a CA, setting up SFTP with openSSH, or anything else would be appreciated.

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• Creating a voxel world with 3D arrays using threads

  - by Sean M.

  I am making a voxel game (a bit like Minecraft) in C++(11), and I've come across an issue with creating a world efficiently. In my program, I have a World class, which holds a 3D array of Region class pointers. When I initialize the world, I give it a width, height, and depth so it knows how large of a world to create. Each Region is split up into a 32x32x32 area of blocks, so as you may guess, it takes a while to initialize the world once the world gets to be above 8x4x8 Regions. In order to alleviate this issue, I thought that using threads to generate different levels of the world concurrently would make it go faster. Having not used threads much before this, and being still relatively new to C++, I'm not entirely sure how to go about implementing one thread per level (level being a xz plane with a height of 1), when there is a variable number of levels. I tried this: for(int i = 0; i < height; i++) { std::thread th(std::bind(&World::load, this, width, height, depth)); th.join(); } Where load() just loads all Regions at height "height". But that executes the threads one at a time (which makes sense, looking back), and that of course takes as long as generating all Regions in one loop. I then tried: std::thread t1(std::bind(&World::load, this, w, h1, h2 - 1, d)); std::thread t2(std::bind(&World::load, this, w, h2, h3 - 1, d)); std::thread t3(std::bind(&World::load, this, w, h3, h4 - 1, d)); std::thread t4(std::bind(&World::load, this, w, h4, h - 1, d)); t1.join(); t2.join(); t3.join(); t4.join(); This works in that the world loads about 3-3.5 times faster, but this forces the height to be a multiple of 4, and it also gives the same exact VAO object to every single Region, which need individual VAOs in order to render properly. The VAO of each Region is set in the constructor, so I'm assuming that somehow the VAO number is not thread safe or something (again, unfamiliar with threads). So basically, my question is two one-part: How to I implement a variable number of threads that all execute at the same time, and force the main thread to wait for them using join() without stopping the other threads? How do I make the VAO objects thread safe, so when a bunch of Regions are being created at the same time across multiple threads, they don't all get the exact same VAO? Turns out it has to do with GL contexts not working across multiple threads. I moved the VAO/VBO creation back to the main thread. Fixed! Here is the code for block.h/.cpp, region.h/.cpp, and CVBObject.h/.cpp which controls VBOs and VAOs, in case you need it. If you need to see anything else just ask. EDIT: Also, I'd prefer not to have answers that are like "you should have used boost". I'm trying to do this without boost to get used to threads before moving onto other libraries.

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• Upgrade to Xubuntu 13.10 - Saucy Salamander

  As a common 'fashion' it is possible to upgrade an existing installation of Ubuntu or one of its derivates every six months. Of course, you might opt-in for the adventure and directly keep your system always on the latest version (including alphas and betas), or you might like to play safe and stay on the long-term support (LTS) versions which are updated every two years only. As for me, I'd like to jump from release to release on my main desktop machine. And since 17th October Saucy Salamander or also known as Ubuntu 13.10 has been released for general use. The following paragraphs document the steps I went in order to upgrade my system to the recent version. Don't worry about the fact that I'm actually using Xubuntu. It's mainly a flavoured version of Ubuntu running Xfce 4.10 as default X Window manager. Well, I have Gnome and LXDE on the same system... just out of couriosity. Preparing the system Before you think about upgrading you have to ensure that your current system is running on the latest packages. This can be done easily via a terminal like so: $ sudo apt-get update && sudo apt-get -y dist-upgrade --fix-missing Next, we are going to initiate the upgrade itself: $ sudo update-manager As a result the graphical Software Updater should inform you that a newer version of Ubuntu is available for installation. Ubuntu's Software Updater informs you whether an upgrade is available Running the upgrade After clicking 'Upgrade...' you will be presented with information about the new version. Details about Ubuntu 13.10 (Saucy Salamander) Simply continue with the procedure and your system will be analysed for the next steps. Analysing the existing system and preparing the actual upgrade to 13.10 Next, we are at the point of no return. Last confirmation dialog before having a coffee break while your machine is occupied to download the necessary packages. Not the best bandwidth at hand after all... yours might be faster. Are you really sure that you want to start the upgrade? Let's go and have fun! Anyway, bye bye Raring Ringtail and Welcome Saucy Salamander! In case that you added any additional repositories like Medibuntu or PPAs you will be informed that they are going to be disabled during the upgrade and they might require some manual intervention after completion. Ubuntu is playing safe and third party repositories are disabled during the upgrade Well, depending on your internet bandwidth this might take something between a couple of minutes and some hours to download all the packages and then trigger the actual installation process. In my case I left my PC unattended during the night. Time to reboot Finally, it's time to restart your system and see what's going to happen... In my case absolutely nothing unexpected. The system booted the new kernel 3.11.0 as usual and I was greeted by a new login screen. Honestly, 'same' system as before - which is good and I love that fact of consistency - and I can continue to work productively. And also Software Updater confirms that we just had a painless upgrade: System is running Ubuntu 13.10 - Saucy Salamander - and up to date See you in six months again... ;-) Post-scriptum In case that you would to upgrade to the latest development version of Ubuntu, run the following command in a console: $ sudo update-manager -d And repeat all steps as described above.

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• Core Data managed object context thread synchronisation

  - by Ben Reeves

  I'm have an issue where i'm updating a many-to-many relationship in a background thread, which works fine in that threa, but when I send the object back to the main thread the changes do not show. If I close the app and reopen the data is saved fine and the changes show on the main thread. Also using [context lock] instead of a different managed object context works fine. I have tried NSManagedObjectContext: - (BOOL)save:(NSError **)error; - (void)refreshObject:(NSManagedObject *)object mergeChanges:(BOOL)flag; at different stages throughout the process but it doesn't seem to help. My core data code uses the following getter to ensure any operations are thread safe: - (NSManagedObjectContext *) managedObjectContext { NSThread * thisThread = [NSThread currentThread]; if (thisThread == [NSThread mainThread]) { //Main thread just return default context return managedObjectContext; } else { //Thread safe trickery NSManagedObjectContext * threadManagedObjectContext = [[thisThread threadDictionary] objectForKey:CONTEXT_KEY]; if (threadManagedObjectContext == nil) { threadManagedObjectContext = [[[NSManagedObjectContext alloc] init] autorelease]; [threadManagedObjectContext setPersistentStoreCoordinator: [self persistentStoreCoordinator]]; [[thisThread threadDictionary] setObject:threadManagedObjectContext forKey:CONTEXT_KEY]; } return threadManagedObjectContext; } } and when I pass object between threads i'm using -(NSManagedObject*)makeSafe:(NSManagedObject*)object { if ([object managedObjectContext] != [self managedObjectContext]) { NSError * error = nil; object = [[self managedObjectContext] existingObjectWithID:[object objectID] error:&error]; if (error) { NSLog(@"Error makeSafe: %@", error); } } return object; } Any help appreciated

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• Synchronizing Asynchronous request handlers in Silverlight environment

  - by Eric Lifka

  For our senior design project my group is making a Silverlight application that utilizes graph theory concepts and stores the data in a database on the back end. We have a situation where we add a link between two nodes in the graph and upon doing so we run analysis to re-categorize our clusters of nodes. The problem is that this re-categorization is quite complex and involves multiple queries and updates to the database so if multiple instances of it run at once it quickly garbles data and breaks (by trying to re-insert already used primary keys). Essentially it's not thread safe, and we're trying to make it safe, and that's where we're failing and need help :). The create link function looks like this: private Semaphore dblock = new Semaphore(1, 1); // This function is on our service reference and gets called // by the client code. public int addNeed(int nodeOne, int nodeTwo) { dblock.WaitOne(); submitNewNeed(createNewNeed(nodeOne, nodeTwo)); verifyClusters(nodeOne, nodeTwo); dblock.Release(); return 0; } private void verifyClusters(int nodeOne, int nodeTwo) { // Run analysis of nodeOne and nodeTwo in graph } All copies of addNeed should wait for the first one that comes in to finish before another can execute. But instead they all seem to be running and conflicting with each other in the verifyClusters method. One solution would be to force our front end calls to be made synchronously. And in fact, when we do that everything works fine, so the code logic isn't broken. But when it's launched our application will be deployed within a business setting and used by internal IT staff (or at least that's the plan) so we'll have the same problem. We can't force all clients to submit data at different times, so we really need to get it synchronized on the back end. Thanks for any help you can give, I'd be glad to supply any additional information that you could need!

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• In Java Concurrency In Practice by Brian Goetz, why is the Memoizer class not annotated with @ThreadSafe?

  - by dig_dug

  Java Concurrency In Practice by Brian Goetz provides an example of a efficient scalable cache for concurrent use. The final version of the example showing the implementation for class Memoizer (pg 108) shows such a cache. I am wondering why the class is not annotated with @ThreadSafe? The client, class Factorizer, of the cache is properly annotated with @ThreadSafe. The appendix states that if a class is not annotated with either @ThreadSafe or @Immutable that it should be assumed that it isn't thread safe. Memoizer seems thread-safe though. Here is the code for Memoizer: public class Memoizer<A, V> implements Computable<A, V> { private final ConcurrentMap<A, Future<V>> cache = new ConcurrentHashMap<A, Future<V>>(); private final Computable<A, V> c; public Memoizer(Computable<A, V> c) { this.c = c; } public V compute(final A arg) throws InterruptedException { while (true) { Future<V> f = cache.get(arg); if (f == null) { Callable<V> eval = new Callable<V>() { public V call() throws InterruptedException { return c.compute(arg); } }; FutureTask<V> ft = new FutureTask<V>(eval); f = cache.putIfAbsent(arg, ft); if (f == null) { f = ft; ft.run(); } } try { return f.get(); } catch (CancellationException e) { cache.remove(arg, f); } catch (ExecutionException e) { throw launderThrowable(e.getCause()); } } } }

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• Singletons, thread safety and structuremap

  - by Ben

  Hi, Currently I have the following class: public class PluginManager { private static bool s_initialized; private static object s_lock = new object(); public static void Initialize() { if (!s_initialized) { lock (s_lock) { if (!s_initialized) { // initialize s_initialized = true; } } } } } The important thing here is that Initialize() should only be executed once whilst the application is running. I thought that I would refactor this into a singleton class since this would be more thread safe?: public sealed class PluginService { static PluginService() { } private static PluginService _instance = new PluginService(); public static PluginService Instance { get { return _instance; } } private bool s_initialized; public void Initialize() { if (!s_initialized) { // initialize s_initialized = true; } } } Question one, is it still necessary to have the lock here (I have removed it) since we will only ever be working on the same instance? Finally, I want to use DI and structure map to initialize my servcices so I have refactored as below: public interface IPluginService { void Initialize(); } public class NewPluginService : IPluginService { private bool s_initialized; public void Initialize() { if (!s_initialized) { // initialize s_initialized = true; } } } And in my registry: ForRequestedType<IPluginService>() .TheDefaultIsConcreteType<NewPluginService>().AsSingletons(); This works as expected (singleton returning true in the following code): var instance1 = ObjectFactory.GetInstance<IPluginService>(); var instance2 = ObjectFactory.GetInstance<IPluginService>(); bool singleton = (instance1 == instance2); So my next question, is the structure map solution as thread safe as the singleton class (second example). The only downside is that this would still allow NewPluginService to be instantiated directly (if not using structure map). Many thanks, Ben

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