Diagnostics for Application Managed EntityManagerFactory leaks.
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Key: OPENJPA-2042
URL: https://issues.apache.org/jira/browse/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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