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From Diego Rodríguez Martín <>
Subject Re: What do I do with a heap dump? (OOM Permgen)
Date Fri, 02 Nov 2007 17:18:47 GMT

    I found a memory leak in commons pool version 1.3 that is affecting 
tomcat 6.0.x as it is the commons pool library embedded in it. I tried a 
workaround using a factory with commons 1.2, but it also showed a memory 
    As far as I know, it has not been resolved, so you could be running 
into this


Greg Vilardi escribió:
> On 2 Nov 2007 at 7:24, Caldarale, Charles R wrote:
>>> From: Peter Crowther [] 
>>> Subject: RE: What do I do with a heap dump? (OOM Permgen)
>>> As far as I know, public enemy #1 for eating PermGen space is 
>>> still developers using the Singleton pattern in their code 
>>> and not having listeners to null out the singleton instance 
>>> when the webapp is undeployed.
>> Analagous use of ThreadLocal is also a subtle contributor to the
>> problem.  The offending references must be cleared at the end of
>> processing of each request, since listeners don't have ready access to
>> the thread pool.
> Thank you for the pointers Peter. We do not have any Singletons in the 
> application nor do we use ThreadLocal. However, we do not seem to be 
> cleaning up the JDBC classes on redeploy. I'll install the 
> SessionListener code that is mentionned in the references in Peter's 
> reply. I'm also using the eval version of yourkit now to see what 
> exactly is attached to each of the 52 WebAppClassLoaders in the dump.
> I'll be back if I get stuck again further down the road. Thank you to 
> all of the people who replied for the pointers and the tool 
> recommendations. 
> 	-Greg

Diego Rodríguez Martín (
ALTIRIA TIC - Servicios SMS - Desarrollo Web
Tel. +34 913311198 - Fax +34 915713993 - Móvil +34 610299750

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