It's possible to configure master-slave configurations of ActiveMQ running within a Geronimo server. However, when a BrokerService is going to be a "slave" instance, brokerService.start() will block indefinitely. In order to support master-slave configurations, I'd like to allow a BrokerService to start asynchronously (not holding up Geronimo server startup).
Note that client configuration (connector/mdb) is a bit tricky... You need to configure clients to use the ActiveMQ discovery or failover protocols. Clients need to be able to find and connect to the master broker. VM or simple tcp-ip configuration won't work.