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.