Re: Tomcat 4.0.x memory leak (not javac)

[William Connor]

We first ran into this bug when hot-deploying JetSpeed - about seven 
times would cause an out of memory w/ the default heap size. JetSpeed 
had so many leaks itself that we dropped down to bares bones test app 
with a servlet, but no JSPs or third party libraries. With this small 
app would could do a hundred or so deploys or reloads before hitting 
out of memory. We purchased JProbe to try and further track down the 
problem. Unfortunately, JProbe appeared to disturb the environment 
enough that things could not clean up properly anyway. At that point we 
gave up the hunt. Although we're still using 4.1.x in production, we 
recently confirmed that the problem still exists in 5.x. In most cases 
we've been running RedHat 8 with a Sun 4.1 JDK, but we've seen the 
problem on Windows and MacOS as well. It is easy to reproduce - we used 
the Ant task to deploy inside a loop. No need to hit any pages or cause 
JSP's to compile, just redeploying will do it.

On Dec 3, 2003, at 7:06 AM, Shapira, Yoav wrote:

Howdy,
Happy holidays hopefully devoid of debugging ;)
Yoav Shapira
Millennium ChemInformatics

-----Original Message-----
From: Trenton D. Adams [mailto:[EMAIL PROTECTED]
Sent: Tuesday, December 02, 2003 4:15 PM
To: 'Tomcat Users List'
Subject: RE: Tomcat 4.0.x memory leak (not javac)
Ok, thanks guys.  I'll see what I can do.  EXTREMELY busy right now,
but I
might be able to try it over christmas holidays. :)  MAYBE!

-----Original Message-----
From: Shapira, Yoav [mailto:[EMAIL PROTECTED]
Sent: December 2, 2003 12:08 PM
To: Tomcat Users List
Subject: RE: Tomcat 4.0.x memory leak (not javac)
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:[EMAIL PROTECTED]
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:[EMAIL PROTECTED]
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:[EMAIL PROTECTED]
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:[EMAIL PROTECTED]
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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