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How To Set Up Apache2 With mod_fcgid And PHP5 On Debian Lenny

Thu, 2011.04.21 - 11:42 — müzso
http://www.howtoforge.com/how-to-set-up-apache2-with-mod_fcgid-and-php5-on-debia...
A good article, I used to set up FCGI the same way. I had to find all the necessary info myself, when I first tried to use FCGI with a multi-site setup (separate PHP config, etc. for each site), but I'm glad that meanwhile somebody took the time to write it down. Smile

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Wed, 2011.10.26 - 11:27 — müzso

FastCGI (aka. mod_fcgid) and the PHP_FCGI_CHILDREN variable

First things first: you should never set PHP_FCGI_CHILDREN to anything else than 0 if you use it with mod_fcgi. This is pretty well described in the mod_fcgi documentation.
Nonetheless I had this set to 5 for a long time and it did not cause any problems. Recently the server was upgraded from Debian Lenny to Squeeze and the server died even under minimum load. Even a couple (a dozen) PHP requests caused the PHP processes (php5-cgi) to push the CPU to 100% (actually it pushed the wait percentage up as if there was heavy disk I/O ... and soon the system started swapping too as if memory was depleted). I couldn't find the culprit for quite some time, but then came to a post about PHP_FCGI_CHILDREN and how one should set it to zero in case one uses it with FCGI. So I did it and it fixed the problem. The server started acting normal again.

It seems that the mod_fcgid in Lenny (2.2-1+lenny1) and in Squeeze (2.3.6-1) handle PHP_FCGI_CHILDREN a bit differently. At least I did not find anything else to be different (the PHP version was the same before and after the upgrade, because I had to keep the old PHP5 from Lenny since a lot of our PHP sites do not work well with PHP 5.3 and Squeeze has 5.3, Lenny had 5.2).

So today's learning was: always set PHP_FCGI_CHILDREN to 0 in your PHP wrapper script if you use FastCGI (mod_fcgid).

(P.S.: the article linked to this post tells you otherwise ... don't listen to it's bad advice Smile )