Xmodulo posted a tutorial about configuring a Tomcat cluster on Ubuntu

Apache Tomcat is the most popular open-source Java web server. If your web site is expecting more traffic as your business grows, a single instance of Tomcat will probably not scale with the growing traffic. In that case, you might be thinking to run Tomcat in a "clustered" environment, where web server workload is distributed to multiple Tomcat instances.

In this article I will show you how to configure a Tomcat cluster with load balancing and session replication. Before we delve into the details about the setup, we want to clarify some of the terms we will be using in this tutorial.

  How to configure a Tomcat cluster on Ubuntu