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From "Gary Gregory (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LOG4J2-819) PermGen OutOfMemoryError when reloading webapp on Tomcat 6
Date Fri, 12 Sep 2014 16:20:34 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14131710#comment-14131710

Gary Gregory commented on LOG4J2-819:

[~remkop@yahoo.com]: We need something to stop the threads. The clocks own the threads, so
we have to ask the clocks, hence the stop methods.

- Have the threads check some global "is log4j shutting down" flag. Bleh.
- Use a thread pool (with no size limit) for use by all Log4j threads. Creating a thread should
always go through the pool. Then we can shutdown the pool as a whole. This seems like a lot
of work and hard to get right since thread shutdown matters I would imagine. Only enforceable
by coding convention or with some extra Maven tooling. Yikes.

What else?

> PermGen OutOfMemoryError when reloading webapp on Tomcat 6
> ----------------------------------------------------------
>                 Key: LOG4J2-819
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-819
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 2.0.2
>         Environment: Tomcat 6
>            Reporter: Costa Theodosiou
>            Priority: Critical
>         Attachments: gg-log4j2-clocks-interrupts.patch, gg-log4j2-clocks-v2.patch
> When reloading an application 3 or 4 times in Tomcat 6, the application crashes with
a "java.lang.OutOfMemoryError: PermGen space" exception.
> After some investigation using the "When all else fails" section of https://wiki.apache.org/tomcat/OutOfMemory
in conjunction with Java VisualVM, I have narrowed down the problem to the Thread created
within org.apache.logging.log4j.core.util.CoarseCachedClock.
> When a Thread is created, it contains a reference to the classloader that it was created
with. In this case, the Thread's contextClassLoader field contains a reference to the WebappClassLoader.
When Tomcat attempts to unload the webapp, the Thread still holds onto this reference which
prevents WebappClassLoader from being freed.
> Perhaps the Log4jServletContextListener (Log4jWebInitializerImpl) can be made to stop
the CoarseCachedClock thread.
> I believe this is not an obvious issue on Tomcat 7 due to https://wiki.apache.org/tomcat/MemoryLeakProtection.

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