Speeding up Apache through apache2-mpm-worker and php5-cgi on Debian / How to improve Apache performance and decrease server memory consumption

speeding up apache through apache2-mpm-worker and php5-cgi on Debian Linux / how to improve apache performance and decrease server responce time
By default most Apache running Linux servers on the Internet are configured to use with the mpm prefork apache module
Historically prefork apache module is the predecessor of the worker module therefore it's believed to be a way more tested and reliable, if you need a critical reliable webserver configuration.

However from my experience by so far with the Apache MPM Worker I can boldly say that many of the rumors concerning the unreliabity of apache2-mpm-worker are just myths.

The old way Apache handles connections e.g. the mod prefork is the well known way that high amount of the daemons on Linux and BSD are still realying on.
When prefork is a used by Apache, every new TCP/IP connection arriving at your Linux server on the Apache configured port let's say on port 80 is being served by Apache in a way that the Apache process (mother process) parent does fork a new Apache parent copy in order to serve the new request.
Thus by using the prefork Apache needs to fork new process (if it doesn't have already an empty forked one waiting for connections) and serve the HTTP request of the new client, after the request of the client is completed the newly forked Apache usually dies (even though it again depends on the way the Apache server is configured via the Apache configuration – apache2.conf / httpd.conf etc.).

Now you can imagine how slow and memory consuming it is that all the time the parent Apache process spawns new processes, kills old ones etc. in order to fulfill the client requests.

Now just to compare the Apace mpm prefork does not use the old forking way, but relies on a few Apache processes which handles all the requests without constantly being destroyed and recreated like with the prefork module.
This saves operations and system resources, threaded programming has already been proven to be more efficient way to handle tasks and is heavily adopted in GUI programming for instance in Microsoft Windows, Mac OS X, Linux Gnome, KDE etc.

There is plenty of information and statistical data which compares Apache running with prefork and respectively worker modules online.
As the goal of this article is not to went in depths with this kind of information I would not say more on it but let you explore online a bit more about them in case if you're interested.

The purpose of this article is to explain in short how to substitute the Apache2-MPM-Prefork and how your server performance could benefit out of the use of Apache2-MPM-Worker.
On Debian the default Apache process serving module in Apache 1.3x,Apache 2.0x and 2.2x is prefork thus the installation of apache2-mpm-worker is not "a standard way" to install Apache

Deciding to swith from the default Debian apache-mpm-prefork to apache-mpm-worker is quite a serious and responsible decision and in some cases might cause troubles, if you have decided to follow my article be sure to consider all the possible negative consequences of switching to the apache worker !

Now after having said a bunch of info which might be not necessary with the experienced system admin I'll continue on with the steps to install the apache2-mpm-worker.

1. Install the apache2-mpm-worker

debian:~# apt-get install apache2-mpm-worker php5-cgi
Reading state information... Done
The following packages were automatically installed and are no longer required:
The following packages will be REMOVED apache2-mpm-prefork libapache2-mod-php5
The following NEW packages will be installed apache2-mpm-worker
0 upgraded, 1 newly installed, 2 to remove and 46 not upgraded.
Need to get 0B/259kB of archives.After this operation, 6193kB disk space will be freed.

As you can notice in below's text confirmation which will appear you will have to remove the apache2-mpm-prefork and the apache2-mpm-worker modules before you can proceed to install the apache2-mpm-prefork.

You might ask yourself if I remove my installed libphp how would I be able to use my Apache with my PHP based websites? And why does the apt package manager requires the libapache2-mod-php5 to get removed.
The explanation is simple apache2-mpm-worker is not thread safe, in other words scripts which does use the php fork(); function would not work correctly with the Apache worker module and will probably be leading to PHP and Apache crashes.
Therefore in order to install the apache mod worker it's necessary that no libapache2-mod-php5 is existent on the system.
In order to have a PHP installed on the server again you will have to use the php5-cgi deb package, this is the reason in the above apt-get command I'm also requesting apt to install the php5-cgi package next to apache2-mpm-worker.

2. Enable the cgi and cgid apache modules

debian:~# a2enmod cgi
debian:~# a2enmod cgid

3. Activate the mod_actions apache modules

debian:~# cd /etc/apache2/mods-enabled
debian:~# ln -sf ../mods-available/actions.load
debian:~# ln -sf ../mods-available/actions.conf

4. Add configuration options in order to enable mod worker to use the newly installed php5-cgi

Edit /etc/apache2/mods-available/actions.conf vim, mcedit or nano (e.g. your editor of choice and add inside:

&ltIfModule mod_actions.c>
Action application/x-httpd-php /cgi-bin/php5
</IfModule>

After completing all the above instructions, you might also need to edit your /etc/apache2/apache2.conf to tune up, how your Apache mpm worker will serve client requests.
Configuring the <IfModule mpm_worker_module> in apache2.conf is necessary to optimize your newly installed mpm_worker module for performance.

5. Configure the mod_worker_module in apache2.conf One example configuration for the mod worker is:

<IfModule mpm_worker_module>
StartServers 2
MaxClients 150
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
MaxRequestsPerChild 0
</IfModule>

Consider the fact that this configuration is just a sample and it's in no means configured for serving Apache requests for high load Apache servers and you need to further play with the values to have a good results on your server.

6. Check that all is fine with your Apache configurations and no syntax errors are encountered

debian:~# /usr/sbin/apache2ctl -t
Syntax OK

If you get something different from Syntax OK track the error and fix it before you're ready to restart the Apache server.

7. Now restart the Apache server

debian:~# /etc/init.d/apache2 restart

All should run fine and hopefully your PHP scripts should be interpreted just fine through the php5-cgi instead of the libapache2-mod-php5.
Using the /usr/bin/php5-cgi will increase with some percentage your server CPU load but on other hand will drasticly decrease the Webserver memory consumption.
That's quite logical because the libapache2-mod-hp5 is loaded once during apache server whether a new instance of /usr/bin/php5-cgi is invoked during each of Apache requests via the mod worker.

There is one serious security flow coming with php5-cgi, DoS against a server processing scripts through php5-cgi is much easier to be achieved.
An example for a denial attack which could affect a website running with mod worker and php5-cgi, could be simulated from a simple user with a web browser which holds up the f5 or ctrl + r browser page refresh buttons.
In that case whenever php5-cgi is used the CPU load would rise drastic, one possible solution to this denial of service issues is by installing and using libapache2-mod-evasive like so:

8. Install libapache2-mod-evasive

debian:~# apt-get install libapache2-mod-evasive
The Apache mod evasive module is a nice apache module to minimize HTTP DoS and brute force attacks.
Now with mod worker through the php5-cgi, your apache should start serving requests more efficiently than before.
For some performance reasons some might even want to try out the fastcgi with the worker to boost the Apache performance but as I have never tried that I can't say how reliable a a mod worker with a fastcgi would be.

N.B. ! If you have some specific php configurations within /etc/php5/apache2/php.ini you will have to set them also in /etc/php5/cgi/php.ini before you proceed with the above instructions to install Apache otherwise your PHP scripts might not work as expected.

Mod worker is also capable to work with the standard mod php5 Apache module, but if you decide to go this route you will have to recompile your PHP lib manually from source as in Debian this option is not possible with the default php library.
This installation worked fine on Debian Lenny but suppose the same installation should work fine on Debian Squeeze as well as Debian testing/unstable.
Feedback on the afore-described mod worker installation is very welcome!

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12 Responses to “Speeding up Apache through apache2-mpm-worker and php5-cgi on Debian / How to improve Apache performance and decrease server memory consumption”

  1. Chris Chinchilla says:
    Firefox 4.0 Firefox 4.0 Mac OS X  10.6 Mac OS X 10.6
    Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0) Gecko/20100101 Firefox/4.0

    My God, this really worked for me! Thank you so much!

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    • admin says:
      Epiphany 2.30.6 Epiphany 2.30.6 Debian GNU/Linux x64 Debian GNU/Linux x64
      Mozilla/5.0 (X11; U; Linux x86_64; en-us) AppleWebKit/531.2+ (KHTML, like Gecko) Version/5.0 Safari/531.2+ Debian/squeeze (2.30.6-1) Epiphany/2.30.6

      I’m glad it was helpful to somebody, I hope it will be useful to other people out there.

      View CommentView Comment
  2. rsquare says:
    Firefox 4.0.1 Firefox 4.0.1 GNU/Linux GNU/Linux
    Mozilla/5.0 (X11; Linux i686; rv:2.0.1) Gecko/20100101 Firefox/4.0.1

    Yes, thanks for this. My WordPress site would hang sporadically unless I clicked the link a second time, now that problem is gone.

    Also, it should be noted that caching static HTML pages is still one of the best options. It drastically reduces page loading time and CPU load.

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    • admin says:
      Epiphany 2.30.6 Epiphany 2.30.6 Debian GNU/Linux x64 Debian GNU/Linux x64
      Mozilla/5.0 (X11; U; Linux x86_64; en-us) AppleWebKit/531.2+ (KHTML, like Gecko) Version/5.0 Safari/531.2+ Debian/squeeze (2.30.6-1) Epiphany/2.30.6

      yes you’re right, caching is essential 🙂
      Hope to see you around

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  3. beast says:
    Opera 11.50 Opera 11.50 Windows XP Windows XP
    Opera/9.80 (Windows NT 5.1; U; es-ES) Presto/2.9.168 Version/11.50

    Awesome! Thank you so much 🙂

    Hugs from Spain.

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  4. Ashraf Amayreh says:
    Firefox 8.0 Firefox 8.0 Ubuntu Ubuntu
    Mozilla/5.0 (Ubuntu; X11; Linux i686; rv:8.0) Gecko/20100101 Firefox/8.0

    Use fcgid, it’s more stable and better than fastcgi. Check:

    2bits.com/articles/apache-fcgid-acceptable-performance-and-better-resource-utilization.html

    I’ve just finished setting up my server to use fcgid, too early to tell, but seems that memory consumption has dropped down to half!

    Sites are so much faster! I’m a happy man!

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  5. mahdy beygi says:
    Firefox 10.0.1 Firefox 10.0.1 Ubuntu Ubuntu
    Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:10.0.1) Gecko/20100101 Firefox/10.0.1

    thank you , worked on Squeeze too

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  6. Jens says:
    Firefox 14.0.1 Firefox 14.0.1 Windows 7 x64 Edition Windows 7 x64 Edition
    Mozilla/5.0 (Windows NT 6.1; WOW64; rv:14.0) Gecko/20100101 Firefox/14.0.1

    Thank you for the tutorial. It is working great, but I have the problem that it is not working with my subdomain. It gives me the following error: The requested URL /cgi-bin/php5/www/delivery/ajs.php was not found on this server.
    Do you have any idea what might be the problem? I’ve already searched for a solution quite some time but couldn’t get it to work.

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    • admin says:
      Firefox 3.6.3 Firefox 3.6.3 Windows 7 Windows 7
      Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3

      I think problem is in your Virtualhost definition, either there is wrong definition of path to cgi-bin or you will need to link your DocumentRoot defined value, let’s say if it is (/var/www/cgi-bin) /var/www/cgi-bin to /usr/lib/cgi-bin/

      Also try to make sure /php5/www/delivery/ajs.php exists either as file in /usr/lib/cgi-bin/php5/www/delivery/ajs.php or as link from /var/www/cgi-bin

      If this doesn’t work try to make sure /usr/lib/cgi-bin/www/delivery/ajs.php exists or smth.
      I’m not sure if this is help, hope it does.

      Write me if it okay.

      Cya,

      Best Georgi

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      • Jens says:
        Firefox 14.0.1 Firefox 14.0.1 Windows 7 x64 Edition Windows 7 x64 Edition
        Mozilla/5.0 (Windows NT 6.1; WOW64; rv:14.0) Gecko/20100101 Firefox/14.0.1

        Thank you very much for your fast reply. Your guess was absolutely right, I forgot the ScriptAlias for the cgi-bin Directory inside the VirtualHost definition. Added it and fixed the problem instantly. Now all is working fine and hopefully running with increased performance.
        Well then, thanks a lot again!

        All the best, Jens

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  7. admin says:
    Firefox 3.6.3 Firefox 3.6.3 Windows 7 Windows 7
    Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3

    One thing to mention is on some hosts with heavy trafficed servers mod-evasive, creates sometimes problems. So if you're getting issues, try using mpm-worker without mod-evasive.

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