We are facing a unusual behavior with round-robin load balancing on apache when one of the tomcat server is brought down.

Our Setup: we have 2 apache web servers on the front end using mod_jk module for load balancing using round robin for load distribution. We also have enabled session stickyness. This is followed by 4 tomcat servers on which the applications are running.

Sometimes under heavy load, if there is a slowness in our DB tier we find that eventually one of the tomcat goes into a hung state and would need a restart. The moment we bounce the tomcat we see a spike in requests in one of the server and this would also go into hung state and need a restart.

Eventually all the server will face similar condition.

What beats me is why does the Apache transfer the whole load to one server instead of distributing the load.

We are now trying the worker.balancer.method=B to see if this helps to resolve our issue.

Any thoughts on resolving the issue is greatly appreciated.

regards, srayker