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Date: Wed, 02 Jan 2008 19:24:18 +0100
From: Rainer Jung <rainer.jung@kippdata.de>
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To: Tomcat Users List <users@tomcat.apache.org>
Subject: Re: Tomcat status 75 error
References: <477BCC93.50306@orbisuk.com>
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Hi Paul,

Paul Beattie schrieb:
> Hi,
> 
> I have a series of relatively high transaction volume tomcat servers
> which are sporadically hitting thread issues.  We run with with tomcat
> 4.1.27 at the current time.  The behaviour we notice is after several
> days of around one hundred thousand transactions our tomcat instances
> hang with the catalina.out message of:
> 
> SEVERE: All threads are busy, waiting. Please increase maxThreads or
> check the servlet status75 75
> Stopping service Tomcat-Standalone
> 
> I've done a quite a lot of reading on this and in some cases there is an
> indication that moving to a later tomcat version alleviates the issue. 
> However in many others it indicates that this problem is due solely to
> the code whereby the threads are not exiting cleanly.  We have a classic
> 3-tier architecture and we can see the db connections closing.  I have
> tired reproducing this error on a tomcat 5 environment and I get a
> similar but not identical error:
> 
> org.apache.tomcat.util.threads.ThreadPool logFull
> SEVERE: All threads (15) are currently busy, waiting. Increase
> maxThreads (15) or check the servlet status

If all threads are busy, you can do a thread dump (kill -QUIT) for the
Java process to find out, what they are actually doing. The result goes
into catalina.out. A thread dump contains the full stack for each thread
in the JVM. The Java process will proceed with the usual work after
writing out the stacks. If all threads are busy, either the load is
higher than expected, or the things your threads are doing are running
slower than expected. In the stack you could see e.g. if threads are
waiting for database results etc.

The above message also indicates, that you have only 15 threads
configured. It's quite possible, that this is a somewhat small thread pool.

B.T.W.: 4.1.27 is a little old. If you need to stick with 4.1, there is
4.1.36 already. I'm not saying, that an update will help, but it could
be a good general cleanup thing.

> The tomcat install continues to function correctly after this has
> occurred.   What I would like to know is do the 2 error messages
> correspond to the same underlying issue.  I strongly suspect it is an
> application code issue so I would like to be able to count Tomcat out of
> the loop.
> 
> Thanks,
> 
> Paul

Regards,

Rainer

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