mod_cluster reports "MEM: Can't read node" and "All workers are in error state" for JBoss AS 7.1.1 cluster

Multicast isn't currently allowed on Rackspace Cloud Servers. The traffic volume of multicast traffic ends up overloading the switching layer and it degrades network performance for all traffic.

For this reason the configuration should look something like this:

Apache config:

Listen host:6666

<VirtualHost host:6666>
  EnableMCPMReceive
  <Location /mod_cluster-manager>
    SetHandler mod_cluster-manager
  </Location>
</VirtualHost>

ServerAdvertise is not enabled

JBoss config:

<subsystem xmlns="urn:jboss:domain:modcluster:1.1">
  <mod-cluster-config advertise="false" connector="ajp" proxy-list="host:6666">
    ...
  </mod-cluster-config>
</subsystem>

proxy-list

Defines a comma delimited list of httpd proxies with which this node will initially communicate. Value should be of the form:

address1:port1,address2:port2

advertise

Using the default configuration, this property can by manipulated via the jboss.mod_cluster.proxyList system property.

If enabled, httpd proxies will be auto-discovered via multicast announcements. This can be used either in concert or in place of a static proxyList.

mod_cluster Documentation