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From "Robert L Sowders" <>
Subject Re: load balancing with routing with mod_jk in cluster
Date Mon, 28 Oct 2002 18:40:57 GMT
Here is a nice article that might help with clustering.


Bernd Koecke <>
10/28/2002 01:45 AM
Please respond to "Tomcat Users List"

        To:     Tomcat Users List <>
        Subject:        Re: load balancing with routing with mod_jk in cluster


it seems that you want to use mod_jk on the nodes as balancer. We don't 
use it 
in that way. We have a load balancer in front of our nodes, which has a 
balancer, if the first one goes down. If we want to get your requested 
we had to configure this on our load balancer, not on the nodes. This 
knows nothing about apache, tomcat and mod_jk. So I don't know how to 
manage it 
with mod_jk.

I don't know how your config should work. Because if N1 routes to all 
nodes and N1 goes down, how should your client know, that he had to 
connect to 
N2? You need some logic in front of your cluster, that the clients see 
cluster as one big server. If you want something like standby or hot 
standby you 
must implement this in the front logic, not on the nodes. And I don't know 
this is possible with jk1.

Why do you limit the balancing to N1? Most of the work is done in your 
The balancing is not so hard, that it will bring your node down. If all 
nodes do 
balancing its no problem, if one node goes down.

But may be I don't understand your scenario.


Alexander Piavka wrote:
>  Bernd thanks for your reply.
>  There is one more question i have.
>  I have 3 nodes N1,N2,N3 each runs apache and tomcat. On node N1 i want
> to run lb_worker1 which will route all requests between all nodes.
> All apache servers will send requests to this lb_worker1.
> On node N2 i want to run lb_worker2 which will start routing  all 
> between all nodes ONLY then lb_worker1 goes down.
> I don't know if it is possible to make this configuration in
> file.
>  As i see i on each node workers.proprerties file should have bl_worker
> which will route requests between bl_worker1 bl_worker2. And bl_worker1
> should have very high lbfactor and bl_worker2 very low:
> worker.bl_worker.type=lb
> worker.bl_worker.balanced_workers=bl_worker1,bl_worker2
> but this is probably illegal as load balancers don't have lbfactor,
> and balancers can't have other balancers in their balanced_workers
> property.
>  Please tell me if i can make the above scenario work.


Dipl.-Inform. Bernd Koecke
Schlund+Partner AG
Fon: +49-721-91374-0

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