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From "Jacob Nowosatka (JIRA)" <>
Subject [jira] [Created] (OPENJPA-2042) Diagnostics for Application Managed EntityManagerFactory leaks.
Date Fri, 19 Aug 2011 17:54:27 GMT
Diagnostics for Application Managed EntityManagerFactory leaks.

                 Key: OPENJPA-2042
             Project: OpenJPA
          Issue Type: Improvement
            Reporter: Jacob Nowosatka
            Priority: Minor

EntityManagerFactories can be leaked if they are created with the JSE bootstrap Persistence
class and are never closed, causing an OutOfMemoryException.

One possibility may be to log a warning or otherwise alert the developer when the number of
unclosed EMF's reaches a certain threshold. An extra step could be taken here to track where
the EMF's are being opened and which ones aren't being closed as to show the developer exactly
where in the code the problem is occurring.

There may be a possibility to eliminate this leak by making the references to the EMF's weak
and let the garbage collector clean up the unclosed EMF's. However, in the case that other
objects are being leaked as well, this change may make it harder to detect such leaks.

I ran a simple test that creates a EMF from Persistence. It then creates and closes an EntityManger.
A new EMF is then created without closing the old one, effectively "leaking" it. As expected,
this results in an OutOfMemoryException. When using weak references on the EMF's, I was able
to get the test to run all night without a trace of any heap growth. However, this is only
a very simple test and a test with more Entities/Configurations/etc. may result in heap growth
due to other objects being leaked(as mentioned earlier). My test case is attached.

For comparison, I tried the same test on Hibernate and EclipseLink. Hibernate runs into the
same OutOfMemoryException. EclipseLink does not.

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