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https://issues.apache.org/jira/browse/LOG4J2-819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14131685#comment-14131685
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Gary Gregory commented on LOG4J2-819:
-------------------------------------
You can stop a thread cleanly using:
- a boolean flag
- thread interrupt() and isInterrupted()
I reread _Effective Java_, _Java Threads_, and _Java Concurrency in Practice_
in this area.
Note that the parkNanos API we use in the threaded clocks does not thrown
{{InterruptedException}} which must mean that it handles interruption requests
cleanly.
The argument against using a boolean flag is that the thread will only check
the flag at the top or bottom of its run loop once it comes out of blocking
calls.
I am going to try another patch a la interrupt(), it should be less code.
For the clocks, flag vs. interrupt is a detail the user should not care about
(hopefully).
> 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-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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