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From Joe Baldwin <>
Subject Re: Memory Management using Tomcat
Date Wed, 16 Sep 2009 22:07:33 GMT

Thank you for your patience on this.  This is the worst problem I have  
encountered and I believe that it is probably something I have  
misunderstood (and failed to implement).

> FWIW, I just did a little monitoring with JConsole with my current
> development setup: Eclipse, Jetty, Cayenne 3.0M6, Tapesty 5.1, MySQL.

Yes I am able to monitor with JConsole on my development machine (but  
not yet on the webhost).  With shared cache ON, and testing with  
50-100 concurrent users, it starts out at about 10-15 MB and then  
spikes to 70-100MB.  Most of the time after the Tomcat idle period  
(i.e. 15 min) it GC down to about 20MB-15MB.

> This new application I'm working on sounds similar to yours.  Fairly
> lightweight.  After everything loaded in, I was using 20-21 MB of
> memory and it stayed steady, even after doing about 100 queries in
> Cayenne (I tend to pull back 1-7 records per set-of-queries, but
> closer to 2-3 on average).

The app sounds similar, but my JConsole reports a huge spike which is  
only released after the idle period. (This is with the Cache set to ON.)

>  I'm using session-based data contexts and
> on-demand data contexts.  The memory footprint was fine and I'm not
> caching (I go get fresh data every query).  I'm not sure why you are
> seeing the anomaly you are seeing unless you just need a bit more RAM
> for Tomcat to be stable.

Mike Kienenberger recommended that I handle this via a filter.  I must  
admit that I am still not totally comfortable with BaseContext and  
could have made a mistake.  I did not want to go in this direction  
until I am sure that I have the blue-print for the correct solution.

So how do I implement you session-based data context configuration.   
(Please send explicit code as it appears that I am just using the  
default BaseContext.)


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