Re: Error AH03490: scoreboard is full, not at MaxRequestWorkers.Increase ServerLimit (Apache Users)

On Tue, Nov 22, 2022 at 6:15 PM Mike Dewhirst <miked@xxxxxxxxxxxxxxx> wrote:

Can anyone suggest some mpm_event.conf settings for a lightly loaded DigitalOcean Ubuntu 2022.04 LTS droplet with 8GB of RAM and a "dedicated CPU"?

I just had to restart Apache which crashed around 22:22 UTC. There is 8Mb of the above error in the log.

This is the plain Apache2 error.log rather than the named website error log which only shows expected errors such as reCaptcha errors.

It seems to have started filling the scoreboard 24 minutes after logrotate. The first ten log entries after logrotate are ...

[Tue Nov 22 00:00:01.934987 2022] [mpm_event:notice] [pid 49892:tid 140450581641088] AH00489: Apache/2.4.52 (Ubuntu) OpenSSL/3.0.2 mod_wsgi/4.9.0 Python/3.10 configured -- resuming normal operations
[Tue Nov 22 00:00:01.935032 2022] [core:notice] [pid 49892:tid 140450581641088] AH00094: Command line: '/usr/sbin/apache2'
[Tue Nov 22 00:20:13.411015 2022] [mpm_event:notice] [pid 49892:tid 140450581641088] AH00493: SIGUSR1 received. Doing graceful restart
[Tue Nov 22 00:20:13.514771 2022] [mpm_event:notice] [pid 49892:tid 140450581641088] AH00489: Apache/2.4.52 (Ubuntu) OpenSSL/3.0.2 mod_wsgi/4.9.0 Python/3.10 configured -- resuming normal operations
[Tue Nov 22 00:20:13.514804 2022] [core:notice] [pid 49892:tid 140450581641088] AH00094: Command line: '/usr/sbin/apache2'
[Tue Nov 22 00:23:57.862865 2022] [mpm_event:notice] [pid 49892:tid 140450581641088] AH00493: SIGUSR1 received. Doing graceful restart
[Tue Nov 22 00:23:57.937161 2022] [mpm_event:notice] [pid 49892:tid 140450581641088] AH00489: Apache/2.4.52 (Ubuntu) OpenSSL/3.0.2 mod_wsgi/4.9.0 Python/3.10 configured -- resuming normal operations
[Tue Nov 22 00:23:57.937192 2022] [core:notice] [pid 49892:tid 140450581641088] AH00094: Command line: '/usr/sbin/apache2'
[Tue Nov 22 00:23:59.938800 2022] [mpm_event:error] [pid 49892:tid 140450581641088] AH03490: scoreboard is full, not at MaxRequestWorkers.Increase ServerLimit.
[Tue Nov 22 00:24:00.939954 2022] [mpm_event:error] [pid 49892:tid 140450581641088] AH03490: scoreboard is full, not at MaxRequestWorkers.Increase ServerLimit.

With event, ServerLimit should be larger than MaxRequestWorkers/ThreadsPerChild not equal to it. It only matters when processes exit and are replaced.
This allows slow to exit processes to be managed alongside their replacement processes.

...

<IfModule mpm_event_module>
ServerLimit 16

        StartServers                    16
        MinSpareThreads                 400
        MaxSpareThreads                 250
        ThreadLimit                     64
        ThreadsPerChild                 50
        AsyncRequestWorkerFactor        2
        MaxRequestWorkers               800
        MaxConnectionsPerChild          0
</IfModule>

I would start with ServerLimit 24 or 32. Nothing has to change along with it.