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From Madhur K Tanwani <>
Subject Tomcat 5.5 Load Balancing Rule Classes
Date Mon, 10 Jul 2006 15:40:22 GMT
Greetings to all in my first mail on the list.
I've read the article on "How To Ask Questions The Smart Way" -
will try to adhere to it, but please don't mind a few misses :).

First with some background. This request is regarding the classes that
implements the rules, as used in the rules.xml file in the balancer
webapp that ships with Tomcat 5.5.  I'm configuring a Tomcat setup with one
load balancer and 3 workers in one cluster. The setup details are :

OS : Linux (2.6.11-1.1369_FC4)
Tomcat : 5.5 (all)
JDK : 1.5

I've being studying through the configuration references from :-
- the Tomcat load balancing HOW-To -
- the Tomcat clustering HOW-To -
- an article on - (for Tomcat 5)

However, what I find is that Tomcat 5.5 by defaults supports basic Rule 
like AcceptEverythingRule, URLStringMatchRule etc. I am trying to build a
load balancer which enforces the following :-
    - chooses from the available "alive" workers from the cluster,
      in a Round-Robin / Least-Load-First manner
    - implements session affinity
    - includes fail over support with session replication, so there is 
no loss
      of session data
    - The transition is transparent to the user. Hence, whatever be the
      "redirectURL", the URL in the browser should not change
As you might expect, the problem is that, this kind of behavior is not
available with the the standard Tomcat installation.
Also, is the transparent transition possible?

I read in the load balancer HOW-To that this list is the best place to 
for latest Rule classes and details.
I've also browsed through the archives, till April 2006 (it was then that I
realized that a search feature there would greatly help!), but did not get
this answer.
I also realize that I can implement the org.apache.webapp.balancer.Rule
interface to generate Rules that I want (in fact that is what the article
on OnJava has provided).

But what I was inquisitive about was whether such standard Rule classes
have been implemented? Are there any pointers to such resources?

On another note, I wanted to ask the clustering and load-balancing gurus,
whether I've taken up the correct approach. I see that many load balancing
tutorials focus on Apache as the load balancer with Tomcat as the worker
in clusters. But since most of them are old, I assume the new Tomcat 5.5
features did not make it then - hence the question.

Please could anyone on the list, help me with these problems? Any 
pointers to
resources would be a great help. In case there is anything else that 
must have
mentioned that would ease thinking on the problem, do ask me for it.

Thanks a lot,

Madhur Kumar Tanwani

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