Configuring mod_cluster to have JBoss nodes disabled by default on join

Issue

• When we start or restart a JBoss node, it joins with mod_cluster and mod_cluster automatically enables traffic to it.  Can we configure mod_cluster so that the node is disabled by default on join, and then enabled once we specify?

Environment

• mod_cluster
• JBoss Enterprise Web Server (EWS) 1.0.x
• JBoss Enterprise Application Platform (EAP) 5.x

Resolution

• This functionality specifically is not yet available.
• You can workaround this default behavior to only manually turn on the node or connect it with mod_cluster when you desire through the following steps:
  • Turn off advertisement and communicate through the proxyList.
  • Once you've disabled advertisement on the httpd and JBoss end, set the proxyList to be some ip/port that is not a valid one for it to join mod_cluster.  You can set this in with the system property jboss.modcluster.proxyList or in deploy/mod-cluster.sar/META-INF/mod-cluster-jboss-beans.xml:

            <property name="proxyList">${jboss.modcluster.proxyList:127.0.0.1:6665}</property>
    

• Now with apache/mod_cluster up, boot up your jboss instance.  It will start but throw an error about not being able to connect to this nonsense proxylist.
• After JBoss is started and you want it to join mod_cluster and become accessible, you can change the proxyList to the correct value.  You can do this by going to the jmx-console and following the "service=ModCluster" link under the jboss.web section.  From here, invoke the addProxy option.  p1 should be the address and p2 the port.  It should then be able to successfully connect to mod_cluster and become accessible.  You should also then remove the initial dummy proxyList value through the removeProxy invocation.
• Note that you can also invoke the addProxy and removeProxy operations through twiddle:

  • 
        twiddle.sh -s 127.0.0.1:1099 -u admin -p admin invoke "jboss.web:service=ModCluster" addProxy 127.0.0.1 6666
        twiddle.sh -s 127.0.0.1:1099 -u admin -p admin invoke "jboss.web:service=ModCluster" removeProxy 127.0.0.1 6665
    

  • Note that for this workaround to work you must use the ModClusterService listener and not the HAModClusterService listener.  If you use the HAModClusterService listener, then when you bring a node back up it will communicate with mod_cluster via the cluster master's valid proxyList, thus enabling it by default.
  Root Cause

  JBoss nodes are enabled by default upon joining with mod_cluster.
  
  
  Thanks,
  Kuldeep Sharma