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From "Bip Thelin" <>
Subject RE: [PROPOSAL Tomcat 4.x] Cluster
Date Thu, 11 Oct 2001 23:16:51 GMT
> -----Original Message-----
> From: Gomez Henri [] 
> Did you ever have considered using the web connector, mod_jk for
> example, to forward serialized stuff from TC to web-server, when
> needed, at answer time ?
> It will help recover from a TC crash when using farm of TC 
> (in load-balancing or fault-tolerant mode) .
> For example :
> Apache server use mod_jk and balance load between TC1, TC2, TC3.
> After a session creation TC1 send both http anwser + 
> serialized session
> data to Apache. When session is updated, TC1 resend session datas.
> TC1 crash and then Apache resend the request to TC2 + the previously
> saved session stuff.
> And it won't need to deploy multicast stuff.
> ajp14 could be extended in such a way.
> What do you think of that ?

It's an interesting idea, I do believe we would need the connectors
and/or a module for TC that does URL/Session rewriting to hide the
different machines in the cluster. Is this already implemented in JK
or have I dreamt that?

Anyway, in your example above you're mentioning 1*httpd and n*TC, if
we have 1 Apache being the "session hub" we would have a singlepoint
of failure which would be as bad as not using clustering at all. I guess
you mean that one shoule also run n*httpd also and cluster the sessions
in between them, with multicast or other technology of choice.

Why I started to go down the multicast-road was because I was looking
at how Weblogic had solved the issue, my first plan was not to make it
as a complete package as Weblogics but somewhere in that direction

I also had some plans on building support for deploying a webapp that
then would get replicated and deployed to every TC in the cluster.

	Bip Thelin

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