Apache’s mod_jk has nice load balancing features. They work quite well for me with Jboss. The basic configuration is to install Jboss on several machines and have an Apache to load balance them.
But while the load balancing is good, the Apache machine becomes a single point of failure. I was asked how to overcome that. The main principle I want keep is the “keep it simple, stupid” principle.
Doing a round robin DNS between two machines is nice, but doesn’t really provides real the load balancing (as it always does 50/50). It also doesn’t check for the the load before it does the balancing.
Other options like using mod_backhand and mod_proxy_balancer all leave me with the same single point of failure problem. That’s why I prefer to use an active/passive cluster to make sure Apache can move to another server in case of a failure. The IP address the users get is a virtual (or floating) IP, which can “jump” between the cluster nodes.
There are several ways to create that cluster, but that’s probably for another more general post.
I’ll be happy to hear other opinions…
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