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From Michael Ludwig <mil...@gmx.de>
Subject Re: Tomcat stops responding
Date Sun, 19 Dec 2010 21:24:41 GMT
Mark Thomas schrieb am 19.12.2010 um 17:43 (+0000):
> On 17/12/2010 12:52, K J.Sreekumar wrote:
> > 
> > This is the problem -
> > 
> >    1. Our tomcat 6 server (version 6.0.29) does not respond
> >    after working for a couple of days. Browsers are unable to
> >    find application URLs (which were previously processed
> >    normally).
> >    2. The logs does not show any error.
> >    3. There are only a total of 50-60 threads in the thread
> >    dump, mostly in WAIT state. Also, it does not show any
> >    BLOCKING or LOCKED threads.
> >    4. Memory utilization was 400MB only
> >    5. TOMCAT restart does not fix the problem. The machine needs
> >    to be restarted to resume normal operation.
> >    6. Netstat did not reveal any extraneous connections

> > Have anybody here faced similar issue before ?
> 
> Frequently.
> 
> Usually a mis-match between the number of threads configured in
> httpd and the number of threads configured in Tomcat. Since mod_jk
> and mod_proxy use persistent connections by default and the BIO
> connector uses one thread per connection then if httpd has more
> threads configured you can eventually reach a state where all
> Tomcat's threads have been allocated and  the next request blocks.

Ah. Did you infer that from the OP's description of most threads
being in the WAITING state?

http://download.oracle.com/javase/1.5.0/docs/api/java/lang/Thread.State.html

> There are two possible approaches.
> 1. Tune the time-outs
> 2. Disable connection re-use
> 
> I'd go with 2 - it takes much less time to set up. Ignore the dire
> warnings in the docs. Most users don't notice the difference.

Here's another take on the same matter from two years ago:

Re: mod_jk -> ajp hangs indefinitely on some requests - Rainer Jung
http://www.mail-archive.com/users@tomcat.apache.org/msg54056.html

-- 
Michael Ludwig

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