Underused Apache server raise MaxRequestWorkers reached: memory leak

apache-2.4memory leak

On an Ubuntu server with 1Gb of RAM, an Apache 2.4.7 server with default configuration started to occasionally stop responding to request. It's used for a personal cloud + other needs and a low traffic website.

An error.log examination revealed this pattern that seem recurrent each time the problem appears:

[mpm_prefork:error] [pid 31950] AH00161: server reached MaxRequestWorkers setting, consider raising the MaxRequestWorkers setting

after which access.log doesn't log any access at all.
Then a day later:

[mpm_prefork:notice] [pid 31950] AH00171: Graceful restart requested, doing restart

which apparently didn't make any difference.

I've had to restart the server manually each time.

Now I'm looking at mpm_prefork.conf, which is default and from the info I've been able to gather, I don't think I need to change anything.
I've started suspecting there could be some memory leak and read that MaxConnectionsPerChild 1000 is kind of a hack to prevent memory leak, so I put it to this 1000 value and will see how it behaves.
Since it's once in a while error, it's difficult to understand what's causing the problem exactly.

Do you think using MaxConnectionsPerChild in this context is a good strategy (hoping the memory leak will be fixed in further release of the site I'm hosting), or does this just not indicate a memory leak?

NB:
Having an average Apache process consuming ~20Mb of memory, I reduced the MaxRequestWorkers from 150 to 30 (considering 500Mb of mem available for Apache on the server).
I have now:

<IfModule mpm_prefork_module>
        StartServers              5
        MinSpareServers           5
        MaxSpareServers           10
        MaxRequestWorkers         30
        MaxConnectionsPerChild    1000
</IfModule>

I don't think the memory peaked out, but as my Munin client was down, I realize now, I can't exclude it.

Best Answer

Removing Owncloud 8.0.0 from my document root directory is the ultimate answer. After that Apache just works as expected...

It would have been good to understand what was causing the problem though and how to configure Apache so that it can handle problematic PHP application. It's disappointing that MaxConnectionsPerChild is not able to handle the problem in this case, but again, I'm not sure what happened really, even though the MaxRequestWorkers error log seemed to indicate the number of thread was the issue.

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