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Chapter 10. Using the mod_cluster Services in EAP 6

The mod_cluster modules provides dynamic load balancing between web contexts on a JBoss application server and an Apache web server.
There are two halves to creating a cluster with mod_cluster: configuring the module on JBoss to manage the web applications and configuring the module on Apache to manage sessions and routing.
JBoss ON can manage the embedded mod_cluster subsystem for JBoss EAP 6 for both domain servers and standalone servers.

10.1. About mod_cluster and JBoss ON

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.
The mod_cluster Topology

Figure 10.1. The mod_cluster Topology

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.

Note

Information about mod_cluster in general is available with the mod_cluster project documentation.
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.