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From "Hubbert, Thomas" <>
Subject jk2 cluster groups
Date Fri, 21 May 2004 14:31:04 GMT
Hello There,

I finally managed to install and configure modJk2 with Apache 1.3 and Tomcat
5. It's running fine and the new graceful shutdown functionality is doing a
good job :-)

Now I want to set up in memory session replication. The problem I see with
that is when I shutdown the first node, deploy the new code and restart it I
would have two nodes running on a different code basis trying to replicate
session information. The newly started Tomcat instance gets all the session
data from the running node before it eventually opens all the ports and lets
people connect to it, doesn't it?! There's now switch enabling me to
activate and deactivate session replication on runtime (like JK2 offers
configuration reloading by accessing the jkstatus page). Please correct me
if I'm wrong...

Assuming the above I think I'll need FOUR tomcat instances (1a, 1b, 2a, 2b)
to implement a real failover solution. I would assign two instances to one
group (1a, 1b) and the other two to a second group (2a, 2b). The tomcat
instances would replicate session states just with other instances in the
same group, i.e 1a with 1b and 2a with 2b respectively. This way I would be
able to graceful shutdown one group (e.g. group 1) and deploy the new code
without affecting the other group (e.g. group 2). Also one of the tomcat
instances could fail (e.g. 1a) because there is always a 'backup node' in
the same group (1b).

Now the question (sorry for the long introduction to my problem):

How can I assign the tomcat instances to different groups running under the
same loadbalancer? Is that possible at all or is there a better solution for
the scenario described above? 


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