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    Apache 'MaxClients exceeded' error.

    • Article Type: General
    • Product: Aleph
    • Product Version: 16.02

    Description:
    Since a month or two our Webopac is suffering from an overload of HTTPD daemons which is resulting in a Apache 'MaxClients exceeded' error.

    We're closely monitoring\analyzing every case but we're not able to get the source of the problem.

    -It seems that number of WWW users is not a problem. Approx.30-40 users when problem occurs which should be no problem.

    -In the weblog we notice that some requests are taking a very long time or are never ending
    Notice this small sequential sample where the second request has ran for 4 minutes:
    145.107.0.161 - -

    "GET / HTTP/1.1" 200 340
    194.171.49.128 - -

    "GET /F/YMT22X3GL9K6BQK18LAAEQEUJY781XRJDTQB79BAKIRFD55YDI-03325?func=short-filter-y&start_date=1990&end_date=9999 HTTP/1.1" 503 323

    -In apache config we already adjusted the MaxClients but this only delays the problem of reaching the MaxClients
    Sample of our current apache config:
    Timeout 300
    KeepAlive Off
    MaxKeepAliveRequests 100
    KeepAliveTimeout 15
    MinSpareServers 5
    MaxSpareServers 10
    StartServers 5
    # MaxClients 150
    #MaxClients 200
    #edu 29-9-2006 opgehoogd
    MaxClients 250
    MaxRequestsPerChild 30

    -When we look at the www_server logs it looks like the connection is of type 'keep alive' although
    in the main config we have 'KeepAlive Off'
    Sample of www_server.log:
    Header: Keep-Alive <300>
    Header: Connection <keep-alive>
    Header: Referer <http://aleph.library.uu.nl/>

    -The only things changed last months are the servicepack levels and adding SFX connectivity.
    We are on servicepacklevel 1712

    Resolution:
    The MaxRequestsPerChild 30 is too low.

    Please try to raise the limit to 1000 and see if it helps.

    The MaxClients limit can be higher than 255 by enlarging the HARD_SERVER_LIMIT (TO 512 OR EVEN 1024) in .../include/httpd.h and recompile apache.


    • Article last edited: 10/8/2013