In discovering this approach the zip file provided by erricson @ http://www.ericsson.com/mobilityworld/sub/signup/login.html?oid=36443
was very helpful. I rec0mmend you get the download. It would speak about clustering all the tomcats under one umbrella of apache.
But what if you want multiple clusters under one apache. For this you will have to proceed as follows.
2. Say you have 4 workers (i.e. 4 tomcats, machine1.. machine 4) and you want machine1, machine2 into cluster a, and machine 3 & machine4 into cluster B then make the following changes in the workers.prop file
a. enter: worker.machine1.domain=A
Supposing that you need the request to be always server to the same server which served the first request from the browzer then:
../conf/workers.properties : make worker.loadbalancer.sticky_session=true
With scenario 1 + scenario2 done, you have achieved fail save mechanism. i.e. if the server of a cluster fails, then the neighboring servers of the same cluster take care of the request.
Right now i could make 1-cluster & a stand-alone tomcat servers, under one apache HTTP server. I shall update the site in-case i get any issues & how to rectify them.