JMS High Availability

High availability (or failover) clusters are designed to improve availability of services by removing any single points of failure. Nodes in the cluster also provide failover and redundancy capabilities. If one node in a cluster fails, then another node ensures that there is no loss of availability of the service. A logical front-end is responsible for configuring two or more nodes to act as redundant services.

To achieve high availability of JMS services, the JMS Binding Component is available in every instance of JBI runtime. Each instance of JBI runtime is also associated with one application server running in a clustered environment. The deployment of a service assembly is replicated to each JMS Binding Component instance. As a result, multiple consumers or producers are created on connections established by the JMS Binding Component instances to the same JMS broker. The JMS broker can be a standalone broker or a broker in a high-performance cluster of brokers.

Because JMS Binding Component instances are replicated, a crash to one instance does not result in a loss of service. The JMS message acknowledgement protocol guarantees at least once delivery of messages (no loss of messages). In conjunction with XA, exactly once semantics can be achieved. A crash to the JMS Binding Component during message delivery results in the JMS broker detecting a connection loss (lacking of message acknowledgement) and redelivering the message to the next available JMS Binding Component receiving from the same queue. With XA, a crash that leaves behind any in-doubt transactions can be recovered when the JMS Binding Component performs XA recovery in coordination with the JBI runtime and the transaction manager. Therefore, the combination of JMS acknowledgement protocol and XA protocol can support failover and recovery.