When Java debugging what could cause my process to hang

Question

I have a Java server process which does heavy processing. It intermittently stops processing, as in the log stops, and activity ceases but the process is still active.

I have had this happen while debugging a few times. When it does I hit pause/break in the debugger so I can inspect the running threads and look for the cause of the stop. But the pause button doesn't break into the program like it normally does, just sits there. I use IntelliJ IDEA but I'm not sure if it will be the IDE or the JVM that is having the issue.

I try breaking into the program before the issue occurs and it works fine, process stops and I can check through the list of threads.

Does anyone know why a JVM would not respond to a debugging pause/break? And how it might get into that situation? I'm a bit stuck as I have no way of diagnosing this issue without being able to see the program state when it is broken. The logs leading up to the issue show no problems.

Answer 1

Can you connect with JVisualVM? Are your CPU on 100%? We had a equals problem. The application was stop. JVisualVM has not connect anymore. The thread dump with jstack show that all threads are stooped (no differences between multiple thread dumps) but the VM consume 100% CPU. We have change the hardware and the problem was solved. We thing it was a RAM problem and the garbage collection run in a endless loop. But this is only a theory.

Please update me if you can solve the problem.