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From Jeff MAURY <jeffma...@jeffmaury.com>
Subject Re: high CPU usage on tomcat 7
Date Sat, 06 Oct 2012 20:36:52 GMT
Aren't you're clients polling the server, this may cause the session not to
expire even if the user is not using the UI ?

Jeff


On Sat, Oct 6, 2012 at 9:42 PM, Mark Thomas <markt@apache.org> wrote:

>
>
> Kirill Kireyev <kirill@instagrok.com> wrote:
>
> >Thanks for all your thorough advice Shanti! (and everyone else)
> >
> >Here are my findings so far:
> >0) My servlet sessions store a large number (~10s of M) or data in RAM.
> >
> >This is by design, to optimize performance. I can also have ~3K active
> >sessions at any one time. Hence a large heap size.
> >1) When I (1) manually expire inactive sessions through Tomcat web
> >interface and (2) manually hit "Perform GC" through jvisualvm console
> >attached to the tomcat process, everything works great, and the memory
> >is successfully reclaimed, and the used heap  size drops back to what
> >it
> >should be when the application initializes.
> >2) However, this doesn't seem to work automatically. More specifically:
> >     a) Sessions are not expiring without manually doing it (I can see
> >the number growing in the Tomcat web interface). Even though my
> >conf/web.xml says:
> >     <session-config>
> >         <session-timeout>20</session-timeout>
> >     </session-config>
> >    b) A full garbage collection is not being performed unless I do it
> >manually. I'm attaching the GC records from my logs/catalina.out.
> >
> >Any insights?
>
> Session expiration is performed by the background processing thread. What
> is that thread doing (a thread dump - well several over time - will tell
> you).
>
> Fix the session expiration issue and the GC issue will be solved. Note the
> JVM may well not perform a full GC unless it absolutely has to. In fact,
> the JVM may not perform any GC if it doesn't have to.
>
> Mark
>
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-- 
Jeff MAURY


"Legacy code" often differs from its suggested alternative by actually
working and scaling.
 - Bjarne Stroustrup

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