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Date: Tue, 24 Jan 2006 08:52:56 -0500
From: David Smith <dns4@cornell.edu>
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To: Tomcat Users List <users@tomcat.apache.org>
Subject: Re: How can I take a webapp "temporarily out of service" using
 mod_jk?
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Prout John - jprout wrote:

>Hi
>
> 
>
>I am running a JBoss cluster, using tomcat as the Servlet engine. Apache
>and mod_jk provide load-balancing of requests over the machines in the
>cluster
>
> 
>
>I need to be able to replace all the URLs in the webapp with a
>"Temporarily out of service" page during maintenance, and I need to do
>this without making any permanent Apache configuration changes and
>without restarting Apache (Operations is very reluctant to restart
>Apache).
>
> 
>
>Does anyone know a way to do this?
>
> 
>
>I think there may be a way to use the controls on the mod_jk status page
>to redirect all requests for a webapp to a different URL ( the "Route
>Redirect" input) but this is probably wishful thinking - even if does
>allow me to redirect requests, it would probably apply to all the
>webapps in the cluster, which wouldn't meet the requirement. The status
>page teases me by listing all the JkMounts and JkUnmounts, but doesn't
>allow me to change them; adding a JkUnmount dynamically would be a good
>solution.
>
> 
>
>Any Ideas?
>
> 
>
>John
>
>
>  
>

If you have a simple setup (1 tomcat, 1 apache) then you should be able
to just update your apache config to comment out JkMount for that
specific webapp and do a 'apachectl graceful' command to have apache
reload.  Make sure you have some pages in your apache where your webapp
normally resides to nicely inform the user maintenance is being done and
they should come back later.  When traffic isn't being diverted to the
webapp, they will see the mantenance page.  After maintenance is
complete, update apache again (reenable JkMount) and do another
'apachectl graceful' command.  The user's experience should be very nice
with no 404 errors, stack traces, or the like.  They may lose their
session if they are in the middle of a transaction.  Handling session
fail-over will require a second tomcat and clustering.

-David


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