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Method for finding memory leak in large Java heap dumps

Asked 2010-03-24T20:53:27.690
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I have to find a memory leak in a Java application. I have some experience with this but would like advice on a methodology/strategy for this. Any reference and advice is welcome.

About our situation:

  1. Heap dumps are larger than 1 GB
  2. We have heap dumps from 5 occasions.
  3. We don't have any test case to provoke this. It only happens in the (massive) system test environment after at least a weeks usage.
  4. The system is built on a internally developed legacy framework with so many design flaws that they are impossible to count them all.
  5. Nobody understands the framework in depth. It has been transfered to one guy in India who barely keeps up with answering e-mails.
  6. We have done snapshot heap dumps over time and concluded that there is not a single component increasing over time. It is everything that grows slowly.
  7. The above points us in the direction that it is the frameworks homegrown ORM system that increases its usage without limits. (This system maps objects to files?! So not really a ORM)

Question: What is the methodology that helped you succeed with hunting down leaks in a enterprise scale application?

java methodology enterprise legacy-code memory-leaks
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Can you accelerate time? i.e. can you write a dummy test client that forces it to do a weeks worth of calls/requests etc in a few minutes or hours? These are your biggest friend and if you don't have one - write one.

We used Netbeans a while ago to analyse heap dumps. It can be a bit slow but it was effective. Eclipse just crashed and the 32bit Windows tools did as well.

If you have access to a 64bit system or a Linux system with 3GB or more you will find it easier to analyse the heap dumps.

Do you have access to change logs and incident reports? Large scale enterprises will normally have change management and incident management teams and this may be useful in tracking down when problems started happening.

When did it start going wrong? Talk to people and try and get some history. You may get someone saying, "Yeah, it was after they fixed XYZ in patch 6.43 that we got weird stuff happening".

answered 2010-03-24T21:08:27.790

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