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From Kevan Miller <>
Subject PCRegistry ClassLoader memory leak
Date Mon, 16 Jul 2007 21:31:45 GMT
Geronimo is running out of PermGen space in some simple deploy/ 
undeploy scenarios involving OpenJPA. The cause of the problem seems  
to be the _metas table in PCRegistry. _metas is a  
ConcurrentReferenceHashMap with WEAK reference keys and HARD  
reference values. The keys are the PersistenceCapable classes. While  
the values are the metadata for these classes which are maintained by  
the internal Meta class.

The cause of the ClassLoader memory leak is simple -- if any of the  
objects/classes held by the Meta class (e.g. fieldTypes) have also  
been loaded by the same ClassLoader used to load the  
PersistenceCapable class, the PersistenceCapable class (the weak key)  
will never be GCed. The value of the HashMap entry will always  
maintain a hard reference to the ClassLoader. Since the ClassLoader  
will never be GC'ed, the the the pcClass Class object will never be  

The problem can be easily recreated using current Geronimo trunk and  
the Geronimo Daytrader application.


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