Hot Deployment Exhausts the PermGen when the Application Uses Ehcache

Environment

• JBoss Enterprise Application Platform (EAP)

Issue

• Our application uses Ehcache. After a couple of hot deploys of this application, JBoss throws an "OutOfMemoryError: PermGen space".

Resolution

• Refer to Content from ehcache.org is not included.Ehcache documentation on how to properly shut it down. It looks like the CacheManager can be shutdown simply enough along with your application by hooking their ShutdownListener to your app through your app's web.xml:

<listener>
  <listener-class>net.sf.ehcache.constructs.web.ShutdownListener</listener-class>
</listener>

Root Cause

• Ehcache threads (such as the cacheManagerTimer) are still running, keeping the application classloader from collection.
• The CacheManager was not shutdown. If it were, such references and threads should have likely been cleaned up.

Diagnostic Steps

• Troubleshoot as described in Java application "OutOfMemoryError: PermGen space"
• Trace classloaders to GC roots and check for Ehcache references
• Check the status of CacheManager's to determine if they are still alive

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