Last Updated on April 15, 2017 by Dave Farquhar
My problems seem to have become more rare since I started blocking spambots and tuned PHP and Apache but last night my server ran out of memory again and started timing out.
It turns out I still had a critical problem, but one that’s easy to fix with a relatively simple Perl script.
I found a reference to a script called Apachebuddy. Running that, I saw that my MaxClients setting in apache2.conf was likely, under load, to cause Apache to try to use 30% more memory than I have in the system. Never mind that Apache has to share space with a database and an operating system (both somewhat important) on the same box.
So I dropped my MaxClients setting based on the recommendation. (Extrapolating from those results, the default-out-of-the-box Apache settings would use 3.9 GB of memory, which is more than the total available memory in a 32-bit x86 system. Yikes.)
My uptime on Apache when I ran this was artificially low, since Apache had only been running for a few minutes. For a quick fix, that’s fine, but for a more valid test, it would be better to retest after the server has handled some load. The results when Apache had two minutes of uptime were quite a bit different from the results when Apache had 15 minutes of uptime. My site gets enough traffic that 15 minutes seemed to be long enough to get reasonable results. When I first ran it, my largest Apache process was 16 megabytes. After 15 minutes, it was 43 MB, and after 30 minutes, it was 38 MB.
Once I find and correct all of the whacked-out defaults, I need to document all the changes I’ve made in one place. But first I need to get back to the point of not having Windows-like uptimes on my server. Otherwise, all I’m doing is passing along incomplete advice.
David Farquhar is a computer security professional, entrepreneur, and author. He has written professionally about computers since 1991, so he was writing about retro computers when they were still new. He has been working in IT professionally since 1994 and has specialized in vulnerability management since 2013. He holds Security+ and CISSP certifications. Today he blogs five times a week, mostly about retro computers and retro gaming covering the time period from 1975 to 2000.