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Subject: Re: Making fail-over work with PermGen errors
To: Tomcat Users List <users@tomcat.apache.org>
References: <563920B7.60603@ed.ac.uk>
From: Christopher Schultz <chris@christopherschultz.net>
Message-id: <563A6387.9060800@christopherschultz.net>
Date: Wed, 04 Nov 2015 14:59:03 -0500
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Stephen,

On 11/3/15 4:01 PM, Stephen Booth wrote:
> Does anyone have any advice about how to make fail-over work more
> cleanly with PermGen errors (other than the obvious one of not letting
> PermGen errors occur)
> 
> I'm using apache ModProxy to connect to tomcat over ajp with additional
> hot-spare servers confgured for fail-over but if I mess up and let the
> jvm run out of PermGen space then tomcat seems to stay alive enough to
> prevent fail-over but not enough to actually serve any content.

Memory-related errors are always problematic.

Do you have any instrumentation/monitoring to check the liveness of your
Tomcat nodes? Can it detect the OOME condition? If so, you should be
able to notify the load-balancer that something had gone wrong. I'm
unsure of how to do it with mod_proxy_ajp, but mod_jk can be
re-configured externally e.g. by calling curl with a specially-crafted
URL[1].

-chris

[1] https://wiki.apache.org/tomcat/tools/mod_jk.py

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