Prefork MPM configuration not in httpd.conf

Question

I have a memory problem with my EC2 Micro instance which is causing it to terminate my MySQL process.

I've read a lot about tuning Apache to limit the memory consumption and am looking to edit the Prefork MPM settings. Catch is - when I go into httpd.conf, I see no mention of any MPM modules.

I've been looking around and the only reference I can find to it is in /etc/httpd/conf.modules.d/00-mpm.conf where I can see that the prefork module is supposed to be loaded. (LoadModule mpm_prefork_module modules/mod_mpm_prefork.so)

When I do httpd -l , prefork.c is NOT listed.

At this point I'm not sure if the module is loaded/compiled with apache, and if it is - how to configure it. Appreciate any help!

Answer 1

You can check which MPM is running:

httpd -M | grep mpm

You'll see something like:

mpm_prefork_module (shared)

All MPM's (prefork, worker, event) are configured from the file you mentioned:

/etc/httpd/conf.modules.d/00-mpm.conf

I am fairly sure AWS just uses the defaults so there is nothing except loading the module. You can go ahead and add your settings. e.g.

LoadModule mpm_prefork_module modules/mod_mpm_prefork.so

StartServers           5
ServerLimit            256
MaxRequestWorkers      256
MaxConnectionsPerChild 0

You can check https://httpd.apache.org/docs/2.4/mod/mpm_common.html for more options.

I too have had memory issues and looked at configuring MPM to fix the problem however it only reduced the issues and didn't fix the problem completely.

I ended up using the below to set an environment variable:

export USE_ZEND_ALLOC=0

I had no memory issues since.