Chapter 1. Overview

Apache is a well-known web server which can be extended using plug-ins. The Apache Tomcat Connector mod_jk is a plug-in designed to allow request forwarding from Apache httpd Server to a Servlet container. The module also supports load-balancing HTTP calls to a set of Servlet containers while maintaining sticky sessions.

HTTP session replication is used to replicate the state associated with web client sessions to other nodes in a cluster. If one node becomes unavailable, another node in the cluster takes the load of the disabled node. Two distinct functions must be performed:

Sessions state replication is handled by JBoss at the application level (refer to Section 15.1, “Enabling session replication in your application”.

Load balancing, however, requires an external load balancer. A cost effective way of managing load-balancing is to set up a software load balancer using Apache httpd and mod_jk.