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From Maor Yosef <maoryo...@gmail.com>
Subject Re: Tomcat 6.0.26 on Windows server - sessions are not expired
Date Mon, 03 Feb 2014 08:30:05 GMT
Hi.

1. We are aware that 6.0.26 is old, but since there is a large operational
impact, we wont upgrade the tomcat until we will know its definetly an
issue in this specific version
2. You are right, it was my mistake, it causes OOM and not stack overflow,
when we see high sessions count we get exceptions saying "unable to create
new native thread"
3. Looking at the sessions manager, we see a lot of sessions with a
negative TTL - meaning they werent expired, if I manually expire them then
the sessions count decreases.
4. Can you point me to an article on how to configure different background
thread for each container? is it configured in tomcat or should be
implemented in the application?

Thanks,


On Sun, Feb 2, 2014 at 7:38 PM, Konstantin Kolinko
<knst.kolinko@gmail.com>wrote:

> 2014-02-02 Maor Yosef <maoryosef@gmail.com>:
> > Hi,
>
> 1. 6.0.26 is old.
>
> > We are facing issues where the sessions are not being expired
> > and eventually causing a stack overflow.
>
> 2. Non-expiring sessions may cause OOM, but they cannot cause a stack
> overflow.
>
> What are your evidences?
>
> > We see that at some point the sessions get pilled up and we need to
> > manually expire those sessions through the manager application, or
> > until we will restart tomcat but after a few hours / days, sessions
> > will start to get stuck again
>
> 3. Increasing count of session does not mean that sessions do not expire.
>
> Your evidence = ?
>
> > We see it in all the applications that are deployed on tomcat,
> > including the manager application - this rules out (in my opinion) the
> > possibility that its an issue with our application.
>
> 4. Sessions are expired by a background thread. If the thread is stuck
> somewhere (e.g. doing auto-deployment work) it will affect expiration
> of sessions.
>
> Your thread dump = ?
>
> By default there is one background thread that is shared by all
> container levels in Tomcat,  but you can configure a separate one in
> each container (container = Context, Host or Engine).
>
> 5. Web bots that do not support cookies may generate multiple sessions.
>
> See CrawlerSessionManagerValve
>
> Best regards,
> Konstantin Kolinko
>
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