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From "Shapira, Yoav" <>
Subject RE: Clustering / Load Balancer / Session Cookie
Date Thu, 29 Apr 2004 13:57:01 GMT


>So the supplied tomcat load balancer isnt of any use for stateful
>where the cluster is spread accross several machines?

It's of use for stateless sessions mostly, yes.  The intended design is
for it to act is a traffic directory, which it does well.  Furthermore,
you are guaranteed (unless you screw up your own rules somehow) that it
will keep forwarding a request for a given URL to the same host every
time, which means you can do some session stuff.  But I haven't thought
through the next step, support for stateful session replication, yet,
and don't have bandwidth at the moment to do so.  Of course others are
very welcome to contribute to the balancer app: I think it could fill a
sorely needed nice (a pure java software only traffic director).  The
hardware balancer approach is becoming less practical is what I'm
hearing from people in various forums, as our networks and apps become
more and more dynamic.

Yoav Shapira

>-----Original Message-----
>From: Peter Lin []
>Sent: 29 April 2004 14:44
>To: Tomcat Users List
>Subject: Re: Clustering / Load Balancer / Session Cookie
>to paraphrase, you want to have it look like the same machine to the
>browser (ie user).
>the easiest way is to use a hardware load balancer. I've use this
>a couple times in the past and it works well.
>peter lin
>"Dale, Matt" <> wrote:
>I'm currently testing a setup up on 3 machines.
>2 have tomcat 5.0.19, these 2 are clustered with session replication
>have a simple test app.
>The other, also 5.0.19, runs the supplied balancer app.
>I've written a simple round robin rule which passes the requests back
>forth as it should, I can see the sessions being replicated fine in the
>logs so all is ok there.
>BUT my problem is accessing the same session on both machines.
>I'm stumped, I know its not accessing the same session because the
>redirected URL is different but how can I get around this?
>I've tried a using an HTML frame on the balancer machine but that was
>clutching at straws and obviously didnt work.
>Any ideas would be appreciated.
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