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From Grzegorz TaƄczyk <>
Subject [mod_jk] concurrency control problem
Date Wed, 21 Dec 2005 20:03:01 GMT

  My configuration is:
  - single machine with Slackware 10
  - apache 2.0.55 with worker MPM
  - tomcat 5.5.4
  - mod_jk 1.2.15

  Here is my apache<->tomcat configuration

  [user]->[ vhost]-ProxyPass->[localhost vhost]-JKMount->[Tomcat]

  Everything works almost fine, but in some unknown circumstances I
  see in apache status that all workers(1000) are busy in R or W
  state. I have 3 AJP 1.3 connectors defined in server.xml. Total sum
  of acceptCount for them is 400. Why connections over 400 are not
  dropped? What is happening with other connections? Client IP and
  request url are not visible in extended apache status and i'm stuck,
  because I can't see which connections are stale, first ProxyPass to
  public ip or second JKMount to 127.0.01.

  When I check tomcat status I see free threads in one of the
  connectors, but I can't connect him using apache! Its maxThreads
  parameter is 100 and acceptCount 200. There are 30 busy threads.
  (Two other connectors settings are 50/100 and 50/100) and one of
  them is 100% busy. It generates hundreds of short connections and
  probably that is the reason of this situation.

  After few moments problem disappears, beacause there are timeouts
  set in server.xml and But those few moments are
  few minutes and this is serious lost of valuable traffic that I
  would like to avoid.

  Before I also tried to use apache 2.2.0 and mod_proxy_ajp, but there
  is a bug: so
  under load it is impossible to use it.

  I understand that it is not apache-httpd mailing list, but I decided
  to start from here because, before I changed second ProxyPass to
  mod_jk in this configuration, there were almost no problems. Of
  course mod_jk is much faster than standard mod_proxy, so I would
  not like to go back to mod_proxy again.

  Help would be greatly appreciated :)

Best regards,

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