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From Gerwood Stewart <>
Subject RE: Tomcat Memory and Garbage Collection questions...
Date Tue, 03 Nov 2009 10:11:05 GMT

Thanks for the reply. I also missed josephs (unless there is several of these threads going

Hot deployment is what we would like to do. It's not possible as yet because of eventual permgen
memory errors. I also (in general) think it's a good idea to _know what we're doing_ so some
of this is trying to ensure the apps we're building are healthy. 

I think an initial part of the problem is commons-logging. Specifically how we are using it.
We have also found the cas-client-core needed to be updated to 3.1.8 as it had it's own issues.
I've experimented with putting both commons-logging and log4j in the tomcat library and that
appears to work, but from some of the reading you guys have provided I suspect that commons
logging should probably be in the context and log4j in tomcat. 

The comment about programmers pushing to much into session attributes is probably another
candidate, though I suspect that is causing a slow down in the clean up and not a permanent
problem (yet).

Shall continue the search...


From: Elli Albek []
Sent: Tuesday, 3 November 2009 6:56 PM
To: Tomcat Users List
Subject: Re: Tomcat Memory and Garbage Collection questions...

A question:

Do you guys use hot deployment of applications? If you do *not*, then
Joseph’s tips are the first things to look at, in short it is the
application code keeping too many references.

If you do hot deployment, then the number of possibilities goes up
significantly. Now you are also talking about references to class loaders
and memory cleanup at shutdown, which is another topic altogether.

On Mon, Nov 2, 2009 at 1:44 PM, Joseph Morgan <
> wrote:

> I hope Mr. Caldarale answered your question, because you may otherwise
> be looking at the 800lb Gorilla in the room.
> Memory problems within Tomcat could be a number of very hard to see
> things, but some quick candidates are:
> * Programmers caching too much data from the DB (or file system) into
> context attributes
> * Programmers using context attributes to store session data
> * Programmers pushing too much data into session attributes
> * Session timeout is set too high and sessions aren't timing out
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