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From Éric Gauthier <EGauth...@labvolt.ca>
Subject RE: Apache 2.2.3 with mod_jk 1.20 loosing connection with a cluster of two Tomcat 6.0.10
Date Mon, 24 Nov 2008 15:10:52 GMT
Hello Peter,

Thank you for your suggestions.

I forgot to say that even if there is two Tomcat instances running behind an AJP connector,
no load balancing has been enabled. Each Tomcat contains its own set of applications.

-----Original Message-----
From: Peter Crowther [mailto:Peter.Crowther@melandra.com] 
Sent: 24 novembre 2008 09:52
To: 'Tomcat Users List'
Subject: RE: Apache 2.2.3 with mod_jk 1.20 loosing connection with a cluster of two Tomcat
6.0.10

> From: Éric Gauthier [mailto:EGauthier@labvolt.ca]
[...]
> I assume this is a Tomcat issue since the threads are going
> berserk, but I am unsure at this point.
[... good description elided...]

Thanks for a comprehensive description of the problem.

It *may* be an application or environment issue, especially as both app servers fail at nearly
the same time.  Common mode failures such as this could indicate:

- Shortage of memory on the server causing OutOfMemoryException, after which anything could
happen!

I didn't see any OutOfMemoryException in Tomcat logs.

- If your application uses other resources (such as a database), is the database doing anything
unusual at around these times?  Suddenly long response times, down for maintenance, or similar?

Yes they use the same database resource. I will check if anything occurs at this time with
the database.

- If the app is an Internet application, is one of the web crawlers suddenly hitting it with
a massive load and saturating it?

I tried to perform a suddent massive load with JMeter and the only thing it caused (I may
have abused on the concurrent requests) is an OutOfMemoryException and then both Tomcats stopped
responding. But this is not what I am actually experiencing...

- Is the virtual machine being starved of resources at these times due to something else happening
on the host?

The VM is dedicated to webapp hosting. No other VM has the possibility to "steal" resources
to this VM. But to make sure, I will check the resources usage logs for this VM the guys in
charge of that.

All just vague ideas at this point, and I suspect you have already considered and rejected
them!


                - Peter

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