The Java Broker's HA offering became available at release 0.18. HA is provided by way of the HA features built into the Java Edition of the Berkley Database (BDB JE) and as such is currently only available to Java Broker users who use the optional BDB JE based persistence store. This optional store requires the use of BDB JE which is licensed under the Sleepycat Licence, which is not compatible with the Apache Licence and thus BDB JE is not distributed with Qpid. Users who elect to use this optional store for the broker have to provide this dependency.
HA in the Java Broker provides an Active/Passive mode of operation with Virtual hosts being the unit of replication. The Active node (referred to as the Master) accepts all work from all the clients. The Passive nodes (referred to as Replicas) are unavailable for work: the only task they must perform is to remain in synch with the Master node by consuming a replication stream containing all data and state.
If the Master node fails, a Replica node is elected to become the new Master node. All clients automatically failover  to the new Master and continue their work.
The Java Broker HA solution is incompatible with the HA solution offered by the CPP Broker. It is not possible to co-locate Java and CPP Brokers within the same cluster.
HA is not currently available for those using the the Derby Store or Memory Message Store.
 The automatic failover feature is available only for AMQP connections from the Java client. Management connections (JMX) do not current offer this feature.
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