Chapter 10. Using the mod_cluster Services in EAP 6

The mod_cluster module, a subsystem on EAP 6, communicates between the web applications on a JBoss EAP server and an Apache web server. Multiple JBoss EAP servers can be involved in a mod_cluster group, and those servers can be managed servers, standalone servers, or a mix of both.

Only high availability profiles contain the mod_cluster module. For domains, the other-server-group server group is configured to use the full-ha profiles, though any profile which supports high availability can be used (such as the ha profile or a custom profile). For standalone servers, the server must be started with the standalone-ha.xml configuration.

One EAP server within the mod_cluster server is the master node; that is the administering mod_cluster service. Every other member of the cluster is a worker node.

Whether a specific resource belongs to the mod_cluster domain depends on the profile that resource is associated with, which is largely outside of the control of JBoss ON. (Of course, a standalone server can be started with the high availability configuration with the JAVA_OPTS settings in JBoss ON for start scripts, or a new managed server can be created that uses a high availability profile. But the profile definitions themselves are created and maintained outside of JBoss ON.)

JBoss ON manages the mod_cluster configuration itself. The cluster settings include multicast (advertising), load balancing, session handling, and network settings.