Linux CPU usage and montioring using shell memcache and jquery

Recently in a project where the application was deployed across multiple servers, the Client QA as well as Support Team wanted a better monitoring of all the servers in the production. It was too much to provide everybody with shell access and ask them to monitor using top. Well after a lot of digging through the wonderful search index of Google. And with insights from Paul Colby vide his article Calculating CPU Usage from /proc/stat, and various comments of Memcache usage through telnet along with the /dev/tcp socket connections it was just a matter of using some nifty shell processing before I could store each machine cpu values, loadavg, and running tasks as a json encoded string into memcache on one of the hosts with hostname as the key.
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PHP Sessions in Memcache – Locking Issues

Actually it is ages since I sat down to scribble something. Well this one could not be avoided. Hence here it is.

In one of our FTE projects, we had faced a complication that Memcached on one node was using 100% cpu and php-cgi was complainging that the same node was not permitting any more memcached connections. The configuration was as what all says, session.save_handler = memcache, session.save_path = “tcp://:11211,tcp://:11211,tcp://:11211″. It was giving jitters to the night support, that this used to happen at the worse time when most of the clients are using the application. And eventually that memcached needed to be restarted, kicking all users out and every one has to login back from the login page. Now during the past weeks it was so horrible that we marked a portion of the ramdisk from one least loaded nodes and used nfs to export this to all the nodes for a file based sessions store.
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php memcache simulate using file system

Recently we were facing some difficulties, where we had facilitate implementing a copy of an application on a development environment with our client. The most difficult part was that though we could coax php to load libraries, we could not install any system services. We were supposed to install only a web application to a pre-configured virtual host. Since we had enjoyed the facility of having Memcache at our own development environment, some core part of the application which was required only when users are logged in, was using the Memcache. Also our database abstraction layer was heavily depending on the memcache library. We immediately identified that the requirements were not met and specified that the environment was not as we required. But the support people were so adamant that they insisted us to proceed by commenting out all references to the class. Well I can also be tough.
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url shortening script using MariaFramework

Just as a proof of concept, we had tried to port or even rework the whole of asianetindia.com using MariaFramework. The task of migrating the wordpress admin side, being herculian, this was delayed in pushing to production and it is still in poc stage. Now to nail down the fact that MariaFramework is production ready, we need to show off some generic applications. Here comes one, though the commenting in the main application is poor, I hope one can implement this and get running with out much headache.

Download the full script Download

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MariaFramework 0.22 released

The MariaFramework or phpmf has been released with a couple of new enhancements. The MariaFramework portal is updated with some new plugins for phpmf. Will dive into what the details of the plugins are in another post. For the time the enhancements of the all new MariaFramework.
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Compressing php source files for embedded applications

Compressing php code is not been a tough task, and this is not for the purpose of obfuscating or encoding to make closed source distribution. But to create compact files which can be used in embedded web applications

Compressing php code is not been a tough task, and this is not for the purpose of obfuscating or encoding to make closed source distribution. But to create compact files which can be distributed by pasting into inline text, or into email without the need for attaching. The size will be drastically reduced. Actually at Saturn we did this to help us achieve to load a whole application on to a very space constrained flash disk. We were the least bothered about the process cycles taken to evaluate the php files since they will happen only once in a blue moon when the embedded system restarts. I am pretty sure that for closing source, there are other solutions.
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How I got MySQL 5.5 running on Ubuntu 10.04 Server

After referring to all sort of documents online, for getting the src deb and compiling, which always created one or other method of headaches for me, we approached the Oracle recommended method. Downloaded the binary from official oracle downloads. In the actual process I just deviated here and there to suit my preferences. Untarred the binary to /opt/mysql-5.5.15-linux2.6-x86_64, soft linked to this from /usr/local/mysql.

After creating the /etc/my.cnf to my desired settings, I proceeded with the mysql_install_db, which promptly failed complaining about a libaio. Again a bit of googling, found the answer ‘apt-get install libaio1’. Okay the install db went straight. Now the startup script. Copied the script [mysql-base-dir]/support-files/mysql.server to /etc/init.d/mysql. Issued update-rc.d mysql defaults. All was well, the server started smoothly. But Ubuntu did not have path spec for finding the binaries, so did the easy way ln -s /usr/local/mysql/bin/* /usr/bin/. Since we were using the Ubuntu stock mysql-server and client for a long time, most of our shell scripts also expect the same path.
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The famous spinning cursor in bash

Displaying some sort of activity, the hangover from working continuosly on slow desktops are already deep into developers. Well we cannot complain, the users who are our clients or the clients of our clients always want everything very fast. And if we dont tell them about a process being running in the background, they are sure to kick the button again, and again and again. Hence the need to show activity progress, or even a small activity to remind that the system is busy processing some junk, the progress or throbbers cannot be avoided. A similar progress with message for a long running non interactive bash script was needed for me, since we were depending a lot on build kits written in bash.

The ESC sequence is to hide and display the bash cursor. Since the whole script is self running, and do not need any feedback, the cursor is better not displayed. The function at line 7, showProgress will output a message, and show the spinning cursor with full cycle in a second. stopProgess will make sure the progress display is stopped by removing the file touched by it. Only limitiation is that this can be used only in scripts that will run single instance at a time, even on a multi user system.

I prefer writing really temporary files to /dev/shm/ since that reduces harddisk wear and tear, and is real fast being on ram. While digging for something else at my home, accidentally I completed this bit of snippet. Well thought to share the same. Poor at explaining things so please excuse.
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WordPress – preview and modify a theme till we are satisfied

Since we at Saturn provide wordpress as a CMS, and have more than a handful of experienced WordPress customizers, and themeres we have handled several challeges related to WordPress. The latest one being that the client was offered a facelift, and they wanted to preview the progress of integration. I searched the plugin repositories and blogs, found a lot of solutions, which include theme switchers, theme preview, and even suggestions to have a local copy. Well with our client, we could not think of a local copy, since the database dump itself was about 320GB and the images and videows was a whopping 1200 GB. Well after reading through the source of get_option, a wave struck me.



function new_theme_preview(){
    if(isset(
$_COOKIE['ShowNewTheme'])){
        return 
'myNewTheme';
    }
    return 
false;
}
 
add_filter('pre_option_current_theme''new_theme_preview'10);
 


I added the above to the end of an active plugin, then created two files newtheme.php and oldtheme.php, containing code to set and remove the cookie. The files were put into the top level folder. Once I am done with the theming, I could remove all these manually.

// newtheme.php
setcookie 'ShowNewTheme''1');
header("Location: ./");
 
//oldtheme.php
setcookie 'ShowNewTheme'false);
header("Location: ./");