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From kharp...@oreillyauto.com
Subject Limiting threads per context
Date Thu, 03 Jan 2013 14:31:27 GMT

Hello All,

Yesterday we had a Tomcat6 server reach maxThreads and stay that way until
we restarted it.  After researching a thread dump and some log files, we
found one of the applications is creating NullPointerExceptions and
subsequently leaving a TP-ProcessorX in WAITING state indefinitely for a DB
closePreparedStatement return.  As more requests come in for this
application threads are being established and put into BLOCKED state,
waiting on TP-ProcessorX.  Eventually, the server hits maxThreads and stops
serving requests almost entirely.

Obviously the application causing this needs to (and is being) fixed.  But
I'm curious if there is a higher level of protection that could be
implemented to help protect the other applications (contexts) on this
server?  For example, is there a way to specify that a context can only use
X number of request threads?  Or perhaps X number of threads from an
executor?  Et cetera.

I haven't seen anything in the docs that would do this, but it never hurts
to ask.  Here's our server info in case it's helpful:
OS: Ubuntu 12.04 64-bit
Front-end Server: Apache 2.2.22 (mod_ajp to back-end via Balancer setup)
Back-end App Server:  Tomcat 6.0.24 (AJP & HTTP connectors, no executor)
Java -version output:
  java version "1.6.0_20"
  OpenJDK Runtime Environment (IcedTea6 1.9.13)
(6b20-1.9.13-0ubuntu1~10.04.1)
  OpenJDK 64-Bit Server VM (build 19.0-b09, mixed mode)


Thanks,
Kyle Harper

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