Réf. : Re: tomcat hangging problem

[jo...@bnpparibas.com]

cmanolache@yahoo.com wrote:

> I assume this is happening only on SMP machines ( i.e. with multiple
> CPUs).

that is what we suspect here :-(
unfortunately, we only run on SMP AIX machines :-((
dev is done on NT boxes (or whatever, actually), but production machines
are rs6000 boxes (2 to 8 processors).


> My bet is that this is related with the VM/libraries. It can of course be
> a bug in tomcat, like a deadlock or something - but then it would fail
> on all SMP machines.

I think like this.  A strange thing I noticed yesterday: on "hangging
machines", running with "-Xms100m -Xmx200m" seems to hide problem (I
guess hang would occur later, but a less-than-10-minutes process ran all
night long (and was running till somebody (!$*ù#@) reboot)).


> Could you check with the 'latest' 1.3.0 and make sure you have all the
> patches installed  ( pthred.so, etc ). Also, check the version of the
> libraries between the AIX machines that work and those that don't.

I am trying to 'diff' systems, but it's not that easy on aix :-(


> If you get a core dump - again, this is a clear sign something is wrong
> with the VM/libraries. A java program shouldn't be able to coredump
> regardless of the code inside ( unless JNI is used ), and there's nothing
> we can do in tomcat ( even if we find a workaround, some user code can
> crash the server as well ).

I do agree with that: I do not expect any core from a jvm :-(


> Is anyone else running SMP machines ? I remember long time ago a problem
> on linux/smp, but was solved by using a newer VM.


yes, it would help :} anybody ?

> Costin

--
Joseph Vallot


> >
> > Here is the description of current problem I try to solve...
> > I have already mailed to tomcat-user, but since nobody has a beginning
> > of an answer, and since we can't go on production launch anymore, I try
> > here.
> >
> > environment:
> > - AIX 4.3.3 SMP,
> > - JRE 1.2.2 (several builds), then 1.3.0
> > - tomcat 3.2.1, 3.2.3 then 3.3.b2 (sorry, did not try 3.3.rc1 yet!)
> >
> > problem is: tomcat "hangs" after some time (may be 3 minutes or some
> > hours). I mean tomcat is running ("ps" shows it), but no answer is
> > received to requests when tomcat hangs (telnetting it with a http get
> > request results in no response). Even a kill -3 does nothing.
> >
> > Strangely, problem occurs only on _some_ of AIX 4.3.3 machines where I run
> > tomcat.
> > Some machines, with same jre/tomcat/code, run with no problem (well,
> > maybe problem would occur after a much longer time, I don't really know).
> > And I did not met that on winNT4 (with a Sun jdk: I got to try with
> > an ibm jvm).
> > Note that I got a javacore twice, if somebody can interpret it...
> >
> > I wrote a simple servlet which shows tomcat hangging, if that can help:
> > a singleton deals with doGet: first time it launches 'n' threads, each of
> > them will http-request same singleton every 't' seconds and print result to stdout.
> > other request to singleton only prints text/plain string to response's writer.
> >
> > Thanks
> > --
> > Joseph Vallot




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Re: Réf. : Re: tomcat hangging problem

[cm...@yahoo.com]

On Wed, 26 Sep 2001 joseph.vallot@bnpparibas.com wrote:

> > I assume this is happening only on SMP machines ( i.e. with multiple
> > CPUs).
>
> that is what we suspect here :-(
> unfortunately, we only run on SMP AIX machines :-((
> dev is done on NT boxes (or whatever, actually), but production machines
> are rs6000 boxes (2 to 8 processors).

Nice :-)

> > My bet is that this is related with the VM/libraries. It can of course be
> > a bug in tomcat, like a deadlock or something - but then it would fail
> > on all SMP machines.
>
> I think like this.  A strange thing I noticed yesterday: on "hangging
> machines", running with "-Xms100m -Xmx200m" seems to hide problem (I
> guess hang would occur later, but a less-than-10-minutes process ran all
> night long (and was running till somebody (!$*ù#@) reboot)).

Aha. I would bet something is wrong in the GC or memory allocator.

Are you running the _latest_ version of the VM ? Can you file a bug
on this ?

Does it happen with any servlet ( say HelloWorld ) or only with your
application ? Can you create a simple servlet ( that eventually does
some allocation - in case the bug is in the GC ), and see if it
can reproduce the problem ?

Costin