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From "Shapira, Yoav" <Yoav.Shap...@mpi.com>
Subject RE: Tomcat 4.0.x memory leak (not javac)
Date Tue, 02 Dec 2003 19:07:47 GMT

Howdy,
You don't have to know much about "the tomcat under the hood" to
diagnose this.  It's not a problem with the tomcat classes.  What you
need to know is:
- What 3rd party libraries does your application use
- What classes stay in memory after a reload and have a 2nd instance of
them created.

You can use a profiler like Senor Hanik suggested (JProbe, OptimizeIt,
etc.) to find out the latter.  You want to look for a list of objects
whose instance count increases after a reload of your webapp.
OptimizeIt can do heap snapshot deltas which are the perfect tool here.

Yoav Shapira
Millennium ChemInformatics


>-----Original Message-----
>From: Trenton D. Adams [mailto:trenta@athabascau.ca]
>Sent: Tuesday, December 02, 2003 2:08 PM
>To: 'Tomcat Users List'
>Subject: RE: Tomcat 4.0.x memory leak (not javac)
>
>Ouch, LOL.  I don't really know a whole lot about the tomcat "under the
>hood"!
>:)
>
>I can try though.  Do you have a procedure that I should take to find
this?
>Is there a debugging option that I can turn on for tomcat?
>
>> -----Original Message-----
>> From: Shapira, Yoav [mailto:Yoav.Shapira@mpi.com]
>> Sent: December 2, 2003 11:45 AM
>> To: Tomcat Users List
>> Subject: RE: Tomcat 4.0.x memory leak (not javac)
>>
>>
>> Howdy,
>> Since you can reproduce your error easily, can you narrow
>> down which 3rd
>> party library is keeping the references that cause the memory leak?
>>
>> Yoav Shapira
>> Millennium ChemInformatics
>>
>>
>> >-----Original Message-----
>> >From: Trenton D. Adams [mailto:trenta@athabascau.ca]
>> >Sent: Tuesday, December 02, 2003 1:43 PM
>> >To: 'Tomcat Users List'
>> >Subject: RE: Tomcat 4.0.x memory leak (not javac)
>> >
>> >> -----Original Message-----
>> >> From: David Rees [mailto:drees@greenhydrant.com]
>> >> Sent: December 2, 2003 11:01 AM
>> >> To: Tomcat Users List
>> >> Subject: Re: Tomcat 4.0.x memory leak (not javac)
>> >>
>> >> Shapira, Yoav wrote:
>> >> > Besides what Senor Schultz said (which is 100% true),
>> >> > 1. Where is this mentioned in the release notes, and what
>> >> would one have
>> >> > to search for?
>> >>
>> >> Under KNOWN ISSUES IN THIS RELEASE it does mention issues
>> during web
>> >> application reloading where shared libraries keep references
>> >> to objects
>> >> instantiated by the web application.  That says "memory leak" to
me
>> >> although it doesn't specifically say that.
>> >>
>> >> > 2. You mentioned in your passage the bug was marked as invalid
or
>> >> > wontfix, and the bug you gave below is marked as new.
>> So if anyone
>> >> > actually wasted time (like me) looking up what you said, they
>> didn't
>> >> > find it.
>> >>
>> >> All I did was search for "memory leak" under Tomcat 4 and all
>> >> status.  I
>> >> was not positive that it was marked WONTFIX, I should have
>> clarified
>> >> that in my original message.  I had thought that the issue
>> >> was something
>> >> inherent to the design of Tomcat 4 (which was overhauled in
>> >> Tomcat 5),
>> >> but I'm sure that they are willing to accept patches if
>> >> anyone can fix
>> >> it.  ;-)
>> >
>> >Bugzilla is obviously not working sometimes.  I searched for "memory
>> leak"
>> >one
>> >time and got it.  Then I went to search for it for someone else so I
>> could
>> >give them the bug number but nothing came up.  I did the exact same
>> search,
>> >"memory leak".  Very interesting indeed.  Heck, I even searched for
>> just
>> >"memory" or "leak" once each and came up with nothing.
>> >
>> >>
>> >> -Dave
>> >>
>> >>
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