Question

I have several background tasks running on my Glassfish server implemented by @TimerService instances. The goal of these services is to extract data from files and insert that data into the database.

I tried initially to do this in JPA but the system stalled far to easily, I have now converted the process to JDBC which is far more responsive. However there are still enormous memory leaks somewhere along the way which I cannot pinpoint.

Each file is extracted in a method which manages its own transactions (1 file = 1 transaction). I would think that once this method finalises all variables loose scope and be GC’ed, but this is not the case. After a very short time I am experiencing OutOfMemoryException.

I am wondering if, how, and why Glassfish would be keeping reference to my variables (which are very heavy objects). What settings or methodologies can I apply to minimize these memory leaks?

For reference I am using the stock Glassfish settings with a couple of modifications :

-XX:+CMSPermGenSweepingEnabled 
-XX:+CMSClassUnloadingEnabled 
-XX:MaxPermSize=256m
–XmX1024m

Answer 1

You might be dealing with a class loader leak. JAXB can do this when you’re unmarshalling. To find out for sure you should use a memory analyzer. I highly recommend using the Eclipse Memory Analyzer Tool. Just follow a few of the tutorials and you should be able to get it figured out.