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From "Pinaki Poddar (JIRA)" <j...@apache.org>
Subject [jira] Updated: (OPENJPA-285) Multiple deploy/undeploy leaks memory in PCRegistry
Date Tue, 17 Jul 2007 06:36:04 GMT

     [ https://issues.apache.org/jira/browse/OPENJPA-285?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Pinaki Poddar updated OPENJPA-285:
----------------------------------

    Attachment: JIRA-285.patch.txt

This patch 
1. Changes Meta.fieldTypes from Class[] to String[]
2. Adjusts PCEnhancer to the modified method signature
3. Loads each field's type in PCRegistry.getFieldTypes() using the classloader of pc class

 
Tested for regression against OpenJPA testcases.
Performance hit is a concern.



> Multiple deploy/undeploy leaks memory in PCRegistry
> ---------------------------------------------------
>
>                 Key: OPENJPA-285
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-285
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: kernel
>         Environment: Geronimo
>            Reporter: Pinaki Poddar
>         Attachments: JIRA-285.patch.txt
>
>
> Kevin Miller reported:
> 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
GC'able...
> The problem can be easily recreated using current Geronimo trunk and the Geronimo Daytrader
application.
> Patrick Linskey suggested:
> Change PCRegistry.fieldTypes to be String[] instead of Class[], and dematerialize them
as needed.
> Robert Burrell Donkin/Marc Prud'hommeaux  both pointed out that alternatives such as
to
> listen for the death of a ClassLoader and manually unregistering metadata would be more
costly in terms of complexity.
> This patch follows Patrick's suggestion.
> 1. Changes the Meta.fieldTypes to String[] from Class[]
> 2. Adapts the enhanced bytecode accordingly to the modified method signatures
> 3. PCRegistry getFieldTypes() load the fields' declared type using the same loader that
loaded the owner pc class. 
> Note: For a class C and its field f,  CL(c) == CL(f) is not always true. (Kevin Miller)
>           But CL(c) will be able to load declared type of f  either directly or via one
of its parent (Craig Russel)

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