Why does apache have 50+ child processes

Posted on 2005-04-26
Last Modified: 2013-12-15
Running Sarge with Apache2 after startup I can see that there are about 50 or more child processes. Is this normal?

Also MySql has quite a few of them too?
Question by:tom_szabo
    LVL 11

    Accepted Solution

    In the default installation it is normal.
    Depending where Apache is installed, you can edit httpd.conf and adjust MaxChildProccesses
    LVL 2

    Assisted Solution

    Yes its normal u can fine tune the numbers of child process running

    This will guide to fine tune yr apache server

    Timeout 300
    KeepAlive On
    MaxKeepAliveRequests 100
    KeepAliveTimeout 15
    MinSpareServers 5
    MaxSpareServers 10
    StartServers 5
    MaxClients 150
    MaxRequestsPerChild 0

    Prior to Apache 1.3 the MinSpareServers, MaxSpareServers, and StartServers settings all had drastic effects on benchmark results. In particular, Apache required a "ramp-up" period in order to reach a number of children sufficient to serve the load being applied. After the initial spawning of StartServers children, only one child per second would be created to satisfy the MinSpareServers setting. So a server being accessed by 100 simultaneous clients, using the default StartServers of 5 would take on the order 95 seconds to spawn enough children to handle the load. This works fine in practice on real-life servers, because they aren't restarted frequently. But does really poorly on benchmarks which might only run for ten minutes.

    The one-per-second rule was implemented in an effort to avoid swamping the machine with the startup of new children. If the machine is busy spawning children it can't service requests. But it has such a drastic effect on the perceived performance of Apache that it had to be replaced. As of Apache 1.3, the code will relax the one-per-second rule. It will spawn one, wait a second, then spawn two, wait a second, then spawn four, and it will continue exponentially until it is spawning 32 children per second. It will stop whenever it satisfies the MinSpareServers setting.

    This appears to be responsive enough that it's almost unnecessary to twiddle the MinSpareServers, MaxSpareServers and StartServers knobs. When more than 4 children are spawned per second, a message will be emitted to the ErrorLog. If you see a lot of these errors then consider tuning these settings. Use the mod_status output as a guide.

    Related to process creation is process death induced by the MaxRequestsPerChild setting. By default this is 0, which means that there is no limit to the number of requests handled per child. If your configuration currently has this set to some very low number, such as 30, you may want to bump this up significantly. If you are running SunOS or an old version of Solaris, limit this to 10000 or so because of memory leaks.

    When keep-alives are in use, children will be kept busy doing nothing waiting for more requests on the already open connection. The default KeepAliveTimeout of 15 seconds attempts to minimize this effect. The tradeoff here is between network bandwidth and server resources. In no event should you raise this above about 60 seconds, as most of the benefits are lost.


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