February 10, 2022

How to fix apache coredumps in OTRS / Znuny

In this article you find a solution for Apache coredumps with OTRS or Znuny.

The common coredump issue

You get regularly Internal Server Errors like this during you are writing or sending new tickets, adding new notes or simply linking or merging tickets?

And in this moment you see in your /var/apache/error_log messages like this?

[core:notice] [pid 116:tid 14054] AH00051: child pid 116695 exit signal Segmentation fault (11), possible coredump in /etc/apache2

Distributions use a common multi processing module (MPM) as default for the default Apache package installation. E.g. under Ubuntu 20.04 the default setup of Apache is done with mpm_event module. But it could also be mpm_prefork or mpm_worker, depending on your distribution or Ubuntu version. To ensure that you have the right MPM active run this commands

a2dismod mpm_event
a2dismod mpm_worker
a2enmod mpm_prefork

And finally you need configure your /etc/apache2/mods-enabled/mpm_prefork.conf with values matching to your environment size. This config is e.g. for a small environment with about 50 users.

<IfModule mpm_prefork_module>
        StartServers             5   # how many servers shall be intialized on start
        MinSpareServers          5   # how many servers shall be free for new users
        MaxSpareServers          10  # how many server are allowed for new users to wait
        MaxRequestWorkers        50  # how many servers allowed to start at all, be careful with mem here!
        MaxConnectionsPerChild   100 # kill server after 100 connections to avoid mem leaks
</IfModule>

If you have more users working in parallel on your OTRS/Znuny modify the servers and workers accordingly. But be careful to have enough RAM for your configuration! You can also read more about tuning here Performance-Tuning

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