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From "Bryan Pendleton (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-666) Enhance derby.locks.deadlockTrace to print stack traces for all threads involved in a deadlock
Date Wed, 16 Nov 2005 01:38:28 GMT
    [ http://issues.apache.org/jira/browse/DERBY-666?page=comments#action_12357750 ] 

Bryan Pendleton commented on DERBY-666:

Argh. I hate getting old. Anyway, after following about 50 dead-end ratholes involving tweaking
the build scripts, I finally took Mike's advice and just hand-compiled the one file with the
suggested code to call Thread.getAllStackTraces, and built a system that I could play with.

The good news is that this worked, and I was able to run this code, and sure enough it produces
the stack traces!

The bad news is that, in doing the experiment, I realized that in my environment this feature
is of no use, for I am running in a Network Server environment, and so the result is that
I get the stack traces of the *server*, and what I want are the stack traces of my various
*client* threads.

Duh. Should have been obvious, but, as I say, I'm getting old.

I'm going to try writing a simple JDBC embedded app to verify that this does actually work
correctly in the embedded case, and that it gets useful stack traces in that case, and then
I'll at least have done *something* useful, even if I now realize that I can't use this feature
for the case that I really cared about (my production system, which runs in NetworkServer

Thanks to everybody for their help so far. :)

> Enhance derby.locks.deadlockTrace to print stack traces for all threads involved in a
> ----------------------------------------------------------------------------------------------
>          Key: DERBY-666
>          URL: http://issues.apache.org/jira/browse/DERBY-666
>      Project: Derby
>         Type: Improvement
>   Components: Store
>     Versions:
>     Reporter: Bryan Pendleton
>     Priority: Minor

> I was reading http://www.linux-mag.com/content/view/2134/ (good article, btw!), and it
> >   The next two properties are needed to diagnose concurrency (locking and deadlock)
> >
> >      *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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