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From Robin Wilson <rwil...@kingsisle.com>
Subject RE: TOMCAT GC Issue
Date Wed, 20 Jan 2010 15:35:39 GMT
I agree with Peter, we need more information.

I will point out that we had a similar issue - during peak activity on our site, and it related
to sessions being created faster than Tomcat could get rid of them (even though they were
expired already). We used the "/manager/html" app that comes with Tomcat (you have to leave
the '/manager' webapp installed) to view the number of sessions - and noticed that they were
growing exponentially during our peak loads.

Also, if you are clustered, remember that your sessions are being replicated across all 4
Tomcats - so 1/4 of the load on each server will fill up the heap space as fast as 4X load
on 1 server would...

Check your heap size (-Xmx=? in your 'catalina.sh' or 'catalina.bat' file)... As Peter mentioned,
that will be necessary to figure out what the problem is.

--
Robin D. Wilson
Director of Web Development
KingsIsle Entertainment, Inc.
CELL: 512-426-3929
DESK: 512-623-5913
www.KingsIsle.com


-----Original Message-----
From: peter.crowther3@googlemail.com [mailto:peter.crowther3@googlemail.com] On Behalf Of
Peter Crowther
Sent: Wednesday, January 20, 2010 4:58 AM
To: Tomcat Users List
Subject: Re: TOMCAT GC Issue

2010/1/20 Paulwintech <paulwintech@gmail.com>

>
> Hello,
>
>   I am new to the Tomcat Administration, I have some 4 production servers
> running Tomcat6.x with Jdk - To monitor all my applications like
> Apache,Tomcat and Mysql we are using OPmanager-Application manager tool.
>
>   Intermediately i get GC critical alert. That means some times GC
> collection goes high and remains for more than 10 mins. Then it clears the
> Grabage. But this is happening recently checked all possible logs found
> nothing. This is not happening every time, Say like twice in a day.......
>
> Could you give us a bit more information?
+ JDK version?
+ What memory and GC settings are set?
+ Does the alert coincide with high usage on the servers?
+ Does it happen on all servers equally?  If not, what factors differ
between the servers?
+ *Exactly* what condition causes the monitor to report the alert?  Feel
free to point us at the web page describing the alert's definition in the
monitor.

Sorry to ask for that lot, but different Java versions can handle GC very
differently, and the options make a difference too.

- Peter

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