Debugging a threads problem

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Chris - 12 Feb 2006 19:22 GMT

I have a webapp which is slowly increasing the number of threads it
consumes. This only happens in production; I can't seem to duplicate the
problem in a test system.

Is there any way to get a JVM to dump information on the current threads?
Specifically, I'd like to know what method or class created each thread and
the time it was created. This might be enough to help me figure out what's
going on.

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Daniel Dyer - 12 Feb 2006 19:46 GMT

> I have a webapp which is slowly increasing the number of threads it
> consumes. This only happens in production; I can't seem to duplicate the
[quoted text clipped - 6 lines]
> what's
> going on.

Ctrl-Break (Windows) or kill -3 (Linux/Solaris) will cause the JVM to do a
thread dump.

In the absence of any other evidence of a bug, I would guess that what you
are seeing is a thread pool that increases in size as the load goes up but
doesn't discard idle threads (instead it keeps them alive ready for the
next time the load spikes).

Dan.

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Daniel Dyer
http://www.dandyer.co.uk

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Chris - 12 Feb 2006 21:46 GMT

>> I have a webapp which is slowly increasing the number of threads it
>> consumes. This only happens in production; I can't seem to duplicate the
[quoted text clipped - 14 lines]
> doesn't discard idle threads (instead it keeps them alive ready for the
> next time the load spikes).

Thanks. Trouble is, this is a production system and I can't do a kill
easily. I'm wondering if there is some function I can run from within the
JVM itself.

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Debugging a threads problem

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