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From "Richard S. Huntrods" <huntr...@nucleus.com>
Subject Would like to monitor memory use offline
Date Sun, 03 Aug 2008 02:18:44 GMT
I've been running Tomcat for many versions now, mostly without incident. 
However with the latest set of upgrades rather "forced" upon me all at 
once (instead of managed more properly), my application appears to have 
a severe memory leak.

System Info: OS is Solaris 10-u5 (2008); java 1.6.0_06-b02; 
apache-tomcat-6.0.16; mysql 5.0.51a-solaris10-x86_64. I have fast 
servers and plenty of memory (8 gigs). I'm running 1 gig stack and 
getting at least 2 GC/stack exceptions per day (sometimes more). Yes - 
it's a user/use triggered leak but I can't trace it further yet.

Of course what is odd is that there was NO memory leak using older 
versions of this stuff (Solaris 10 (2006), java 1.5.x, tomcat 5.5.12, 
mysql 5.0.16). I'm sure the memory leak was there, but it was "well 
masked". On the older system I was running 512 meg stack and it never 
gave GC or stack errors.

So, while I am actively trying to fix the memory leak, I still have to 
maintain these production servers at operatonal status (politics - don't 
ask). However, it's difficult as the memory leak is causing repeated GC 
and "out of stack" exceptions.

What I've noticed recently is that when using the manager application, I 
can watch the memory utilization grow and more memory get allocated (via 
refreshing the page), right up until the stack is used up and the main 
application crashes. However, if I'm watching it grow, and then log on 
to the server and reset tomcat (stop and then start tomcat), the memory 
use is back at the start. Thanks to session persistence, no users are 
"harmed" during this exercise.

So for the moment, while I try and debug the application, I can keep 
things running by having a cron job periodically reset tomcat for me. 
But this is really crude. Until I fix the memory leak, I'd like 
something a little bit more elegant.

SO - my question - is there a relatively easy way to create something 
(say a servlet) to watch the stack *just like I can do manually using 
the manager application* but email me when the stack approaches the 
memory limits?

Thanks,

-Richard



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