Ramblings And Musings

Running XP-Dev.com has its set of unique problems, and it has not always been easy. I’ve always tried to run the whole infrastructure on a shoe-string budget at the same time trying not to compromise on quality.

One of the problems is hardware resource.

The truth is: Apache is a memory hog, and to keep things scalable for serving Subversion repositories, I decided to remove all PHP websites out from apache and run them under nginx and PHP-CGI (sudo apt-get install php5-cgi). To be honest, I did not notice any difference in performance of the web sites (apache/mod_php vs nginx/fastcgi/php-cgi), however, the main motivation of this exercise is to limit the maximum amount of memory that my non-critical PHP web sites take, and at the same ti

me, giving apache more room to grow for serving the Subversion repositories. I could have had two apache installations, and give them different limits (by tweaking MaxSpare*, MaxRequests* and friends), but that’s an outright pain to manage. Moreover, I needed a simple webserver that can just serve static content as well.

And lets not forget the users of virtual private servers (VPS) with limited amount of memory. Nginx and PHP-CGI is a much appropriate solution for those memory limited configurations.

I had a look around, and it was basically down to lighttpd or nginx as a replacement to serve the PHP websites, and I picked nginx as there were some odd bugs with lighttpd serving large files. The FastCGI performance is almost the same (I did not really do any scientific benchmarks). However, the part that really got me sold on these two was that it used a master-slave threading model, rat

her than the (out of date) one thread/process per client model, which does not scale at all. Both of them are event driven, rather than “client socket” driven. BTW, this includes the awesome J2EE web container Jetty (if you use the SelectChannelConnector).

Migrating the websites across from apache to nginx/fastcgi/php-cgi was an absolute breeze and here are a few pointers that will help ease the burden.

Strategy

Just to clarify, in the apache/mod_php world, PHP files are served via the apache process itself. The strategy under nginx is to get nginx to pass on the request to another set of long running php-cgi processes that do the actual PHP processing. The response will then be passed back to nginx, which will send it back to the web browser.

Documentation

Use the English Nginx wiki extensively. There’s a lot of documentation there on configuring and tweaking nginx, especially the module reference pages. Here’s a quick and dirty howto on getting nginx+fastcgi and php-cgi working.

PHP FastCGI Start/Stop Scripts

Save yourself the trouble of writing a custom PHP FastCGI start/stop script. Install lighttpd and use their spawn-fcgi script wrapper. Its really going to save you a lot of painful hours. I wrote a simple wrapper around that script as I wanted PHP cgi to startup on every server bootup, or if I wanted a quick restart of the processes. You might rant to adjust the variables pidfile and cgidir for your setup.

#!/bin/bash

me=`whoami`
if [ $me != "root" ]; then
        echo Not root!
        exit 1
fi

pidfile=/root/php.PID
pid=`cat $pidfile`
cgidir=/var/run/php-cgi
sock=$cgidir/unix.sock

[ ! -d $cgidir ] && echo creating $cgidir && mkdir $cgidir && chown www-data.www-data $cgidir

if [ "$pid" != "" ]; then
        echo Killing $pid
        kill $pid
        rm $pidfile
        sleep 1
fi

[ -f $sock ] && chown www-data.www-data $sock

/usr/bin/spawn-fcgi -f /usr/bin/php-cgi -s $sock -C 5 -P $pidfile -u www-data -g www-data

Stop serving .htaccess

Plenty of web apps out there have built in support for apache, and include .htaccess files in their distribution to reduce the configuration overhead for the installer. However, nginx will serve these files by default, which maybe fine for most of the cases, but its always good practice to deny access to it. Simple config for nginx does the trick

location ~ /\.ht {
    deny  all;
}

Serving PHP files

To serve PHP files, nginx will pass the request to the PHP-CGI handlers.

location ~ .*\.php$ {
	fastcgi_pass   unix:/var/run/php-cgi/unix.sock;
	fastcgi_index  index.php;
	include /etc/nginx/fastcgi_params;
	fastcgi_param  SCRIPT_FILENAME  /home/rs/local/wordpress/$fastcgi_script_name;
}

Notice that I’ve included a /etc/nginx/fastcgi_params file above. This file contains all the regular FastCGI directives, and I’ve put it in a seperate file to avoid too much repetition. The content of the file /etc/nginx/fastcgi_params is below:

fastcgi_param  QUERY_STRING       $query_string;
fastcgi_param  REQUEST_METHOD     $request_method;
fastcgi_param  CONTENT_TYPE       $content_type;
fastcgi_param  CONTENT_LENGTH     $content_length;

fastcgi_param  SCRIPT_NAME        $fastcgi_script_name;
fastcgi_param  REQUEST_URI        $request_uri;
fastcgi_param  DOCUMENT_URI       $document_uri;
fastcgi_param  DOCUMENT_ROOT      $document_root;
fastcgi_param  SERVER_PROTOCOL    $server_protocol;

fastcgi_param  GATEWAY_INTERFACE  CGI/1.1;
fastcgi_param  SERVER_SOFTWARE    nginx/$nginx_version;

fastcgi_param  REMOTE_ADDR        $remote_addr;
fastcgi_param  REMOTE_PORT        $remote_port;
fastcgi_param  SERVER_ADDR        $server_addr;
fastcgi_param  SERVER_PORT        $server_port;
fastcgi_param  SERVER_NAME        $server_name;

Wordpress Rewrite

The final tip is for all those Wordpress junkies out there. To get nice urls for Wordpress, you will need the following rewrite directive. If I’m not mistaken, one will be given to you for apache when you’re setting up custom urls via the admin screen, but not for nginx:

if (!-e $request_filename) {
    rewrite ^(.+)$ /index.php?q=$1 last;
}

And that’s about it. I really do hope these tips will help someone out there. I know it would have shaved a couple hours off my setup time had I known them beforehand.