[jboss-jira] [JBoss JIRA] (WFLY-6376) Class loader leak due to Infinispan ExpirationManagerImpl

[Harald Wellmann (JIRA)]

    [ https://issues.jboss.org/browse/WFLY-6376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13178533#comment-13178533 ] 

Harald Wellmann commented on WFLY-6376:
---------------------------------------

I'm not aware of any region factory, I'm simply using the vanilla {{standalone.xml}} configuration, and my {{persistence.xml}} contains the following:

{code:xml}
      <shared-cache-mode>ALL</shared-cache-mode>
      <properties>
         <property name="hibernate.hbm2ddl.auto" value="create-drop" />
         <property name="hibernate.cache.use_second_level_cache" value="true" />
      </properties>
{code}

Regarding the application class loader, the problem is that {{LazyInitializingScheduledExecutorService}} does not actually create an executor when it is instantiated by WildFly. The executor is lazily created when the first task is submitted on deployment of my application. At that point, the TCCL of the thread submitting the task is set to the application classloader, and any newly started worker thread seems to inherit this TCCL.

To reproduce the issue, simply take {{wildfly-quickstart/hibernate5}} and modify {{persistence.xml}} as above. Deploy and undeploy the quickstart and then take a heap dump and look at any threads named {{pool-x-thread-y}} and inspect their {{contextClassLoader}}.

> Class loader leak due to Infinispan ExpirationManagerImpl
> ---------------------------------------------------------
>
>                 Key: WFLY-6376
>                 URL: https://issues.jboss.org/browse/WFLY-6376
>             Project: WildFly
>          Issue Type: Bug
>          Components: Clustering, JPA / Hibernate
>    Affects Versions: 10.0.0.Final
>            Reporter: Harald Wellmann
>            Assignee: Paul Ferraro
>            Priority: Critical
>
> h3. Scenario
> Given a WAR containing a persistence unit with second level cache and query cache enabled, I'm consistently hitting a Metaspace OutOfMemoryError after redeploying the unchanged application a couple of times.
> Analyzing the situation with Eclipse Memory Analyzer, I found one cause to be WFLY-6348, but even after applying that fix locally, I'm still having a Classloader leak which I can trace to a thread used by Infinispan referencing an obsolete web app classloader as context classloader.
> Just to rule out that this might be related to WFLY-6283, WFLY-6285, I repeated my experiments with a local build of WildFly master (2f11a59aee0dbdd52b65c5c684eafa83c3f418da), with Hibernate locally upgraded to 5.0.9.
> I'm still getting a classloader leak with that build.
> h3. Analysis
> {{org.infinispan.expiration.impl.ExpirationManagerImpl}} uses a {{LazyInitializingScheduledExecutorService}}. Due to lazy initialization, the {{ExecutorService}} and the underlying thread pool is not created until my web app is deployed. Thus, when the {{ExecutorService}} is created, the context class loader is set to the web app class loader, and this appears to propagate to the threads of the executor thread pool.
> When the application is undeployed, {{ExpirationManagerImpl.stop()}} gets invoked to cancel any running expiration task. However, the {{ExecutorService}} is not shut down, the threads remain alive and still keep a reference to the now obsolete context classloader.
> h3. Remarks
> I'm not sure if this analysis is correct, at least I hope there's a clue for WildFly and Infinispan experts to identify the real cause.
> By the way, it would be helpful if all threads created by Infinispan had meaningful names, rather than default names like {{pool-5-thread-1}}.



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