Enhance derby.locks.deadlockTrace to print stack traces for all threads
involved in a deadlock
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Key: DERBY-666
URL: http://issues.apache.org/jira/browse/DERBY-666
Project: Derby
Type: Improvement
Components: Store
Versions: 10.1.1.0
Reporter: Bryan Pendleton
Priority: Minor
I was reading http://www.linux-mag.com/content/view/2134/ (good article, btw!),
and it says:
> The next two properties are needed to diagnose concurrency (locking and
> deadlock) problems.
>
> *derby.locks.monitor=true logs all deadlocks that occur in the system.
> *derby.locks.deadlockTrace=true log a stack trace of all threads
> involved in lock-related rollbacks.
It seems, that, in my environment, the deadlockTrace property does not log a
stack trace of *all* threads involved in the deadlock.
Instead, it only logs a stack trace of the *victim* thread involved in the
deadlock.
I think it would be very useful if the derby.locks.deadlockTrace setting could
in fact log a stack trace of all involved threads.
In a posting to derby-dev, Mike Matrigali noted that an earlier implementation
of a similar feature had to be removed because it was too expensive in both
time and space, but he suggested that there might be several possible ways to
implement this in an acceptably efficient manner:
> A long time ago there use to be room in each lock to point at a
> stack trace for each lock, but that was removed to optimize the size
> of the lock data structure which can have many objects outstanding.
> And creating and storing the stack for every lock was incredibly slow
> and just was not very useful for any very active application. I think
> I was the only one who ever used it.
>
> The plan was sometime to add a per user data structure which could be
> filled in when it was about to wait on a lock, which would give most of what
> is interesting in a deadlock.
>
> The current deadlockTrace is meant to dump the lock table out to derby.log
> when a deadlock is encountered.
>
> I agree getting a dump of all stack traces would be very useful, and
> with the later jvm debug interfaces may now be possible - in earlier
> JVM's there weren't any java interfaces to do so. Does anyone have
> the code to donate to dump all thread stacks to a buffer?
Mike also suggested a manual technique as a workaround; it would be useful to
put this into the documentation somewhere, perhaps on the page which documents
derby.locks.deadlockTrace? Here's Mike's suggestion:
> What I do if I can reproduce easily is set try to catch the wait by
> hand and then depending on the environment either send the magic
> signal or hit ctrl-break in the server window which will send the JVM
> specific thread dumps to derby.log.
The magic signal, btw, is 'kill -QUIT', at least with Sun JVMs in my experience.
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