[eclipselink-dev] Fix Review for bug# 259993 - [branch trunk] - WebSpher

["Michael O'Brien" <michael.obrien@xxxxxxxxxx>]

Developers,
   The following fix is ready for general review and will be checked 
into the EclipseLink trunk branch tonight.

http://bugs.eclipse.org/259993
Full Core/JPA/testing patch
https://bugs.eclipse.org/bugs/attachment.cgi?id=125911&action=diff

Checked into the 1.1 branch under
http://fisheye2.atlassian.com/changelog/eclipselink/?cs=3447

   Code Reviewed: Thank you
      Gordon Yorke, Andrei Ilitchev, James Sutherland

   Cause:
      On WebSphere 7 we hang on a find() after a commit().
      A WebSphere 7.0 (6.1 is ok) em.close() callback in the middle of 
a commit() is causing the entityManager state to be reset before the 
transaction completes.
      The result of this is that we end up having pending changes that 
should have been commited but when committed during ReadObjectQuery on a 
em.find() for example - when we attempt to get a lock - we are blocked 
by the previous acquire() that did not release() because of the WAS 
em.close() that reset our UnitOfWork state - mid transaction.
                       RepeatableWriteUnitOfWork.clearForClose(boolean) 
line:126     
                       EntityManagerImpl.clear() line: 220    
                       JPAEMPool.putEntityManager(EntityManager) line: 
147    
                       
JPATxEntityManager.closeTxEntityManager(EntityManager,boolean) line: 
299      

   Fix:
      Fully clear the entityManager "only" when we are in a non 
*Pending state/lifecycle - in which case we only clear the cache - not 
the em state.
      We allow WebSphere 7.0 to do a partial cache em.clear() during a 
commit() without resetting the entityManager state/lifecycle flag

   Reproduction:
      1 - container manged stateless session bean running on WebSphere 7.0
      2 - persist() and commit() a single entity
      2a - we acquire locks in beforeCompletion()
      2b - during the commit() but before afterCompletion() - WebSphere 
calls em.close() which calls uow.clearForClose()
            - it is here that we clear the em and set the 
state/lifecycle back to 0 (Birth) from 4 (*Pending)

   Details of the fix:
      EclipseLink on WebSphere 7.0 is supported.
      Part 1) uow.clearForClose()
       - we do not fully clear the em on a clear() call unless the 
state/lifecycle of the entityManager is 0,3,5 or 6, if the 
state/lifecycle is 1,2 or 4 (*Pending) we only clear the cache.
       - the em state remains uncleared, the afterCompletion code in 
the transaction commits normally.

      Part 2) uow.mergeClonesAfterCompletion()
      - added code to save the current thread on acquire
      - on a merge we check that the current thread and the current 
thread on the previous acquire are equal - if they are not then we 
overwrite the active thread on the mutex on all acquired locks in the 
mergeManager

   Test Results:  See comments 28-30+ in the bug

   thank you
   /michael