[1] requires that at Transaction completion, the container closes (or
returns to cache), the transaction-scoped persistence context. What is
supposed to happen when the JTA transaction completes in a different
thread than the application thread? For example, if a background thread
calls the Synchronization.afterCompletion() because the tx timeout
period has been exceeded (as some Transaction Managers may do), its not
exactly thread-safe to call EntityManager.close() (see [2]).
Specifically, the application could be in the middle of a persist or
some other EntityManager method, when EntityManager.close() is called.
Related to the above, if a JTA transaction rollback occurs in a
background thread [3], how are the managed entities expected to be
detached without violating the EntityManager thread-safety [2]?
There may be vendor specific solutions but shouldn't we (JPA spec eg)
account for the interaction of thread-unsafe persistence contexts and
the JTA Synchronization.afterCompletion that may be invoked in
non-application (background) threads?
Scott
[1] 7.9.1 Container Responsibilities - After the JTA transaction has
completed (either by transaction commit or rollback), the container
closes the entity manager calling EntityManager.close.
[2] 7.2 Obtaining an EntityManager - An entity manager must not be
shared among multiple concurrently executing threads, as the entity
manager and persistence context are not required to be threadsafe.
Entity managers must only be accessed in a single-threaded manner.
[3] 7.9.2 Provider Responsibilities - When the JTA transaction rolls
back, the provider must detach all managed entities if the persistence
context is of type SynchronizationType.SYNCHRONIZED or has otherwise
been joined to the transaction.