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I recently switched from Apache 2.2 prefork to Apache 2.2 worker, but I have no idea what would be a great MPM config to start with. On prefork, I used :
MaxClients 256
StartServers 190
MinSpareServers 160
MaxSpareServers 220

I'd like to be able to accept at least as much simultaneous requests (190)

Thanks !

PS: Server environment: Debian 5.0, 2x 3.00 Ghz, 4 GB RAM, dedicated to Apache.

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2 Answers 2

Reset to default
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ServerLimit 256 MaxClients 256 StartServers 19 ThreadsPerChild 10 MinSpareThreads 160 MaxSpareThreads 220 MaxRequestsPerChild 10000

This will:

  • Start 190 threads when httpd starts
  • Serve up to 256 simultaneous requests
  • Ensure a min of 160 spare threads
  • Limit a max of 220 spare threads
  • Limit each httpd child process to serving 10,000 requests before replacing it with a new child process. This helps prevent hanging up the apache server in case there are memory leaks in the underlying application.
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  • I'm no Apache expert, but from httpd.apache.org/docs/2.2/mod/worker.html I take it that "MaxClients 256" limits to 256 threads in total. Shouldn't that be higher when a "MinSpareThreads 160" is also enforced. Could your config not be more robust by using fewer parameters and letting Apaches default auto-tuning take care of the rest? Commented Sep 2, 2009 at 16:28
  • jesper makes a good point. The default vaules for those directives are better than what you were using with prefork and the ones I mentioned. The only directive you might want to use is the 'MinSpareThreads 160' as the default is 10. Definitely read the link jesper mentioned as well as httpd.apache.org/docs/2.2/mod/mpm_common.html to help you make the best decision on how to set these directives. Commented Sep 2, 2009 at 16:45
  • whoops, the default MinSpareThreads is 75 NOT 10. Sorry. Commented Sep 2, 2009 at 16:46
  • Thank you for your advice. I set : StartServers 8 MaxClients 1024 MinSpareThreads 512 MaxSpareThreads 1024 ThreadsPerChild 64 MaxRequestsPerChild 10000 I chose greater values since the memory footprint is supposed to be much smaller. I noticed too that when running apachectl configtest (or start/stop) with weird values, it reports the error and auto adjusts the settings. Commented Sep 3, 2009 at 8:52
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Finally, I used the following settings which are working pretty well :

StartServers 8 MaxClients 1024 MinSpareThreads 512 MaxSpareThreads 1024 ThreadsPerChild 64 MaxRequestsPerChild 10000

I chose greater values since the memory footprint is supposed to be much smaller. I noticed too that when running apachectl configtest (or start/stop) with weird values, it reports the error and auto adjusts the settings.

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