| # JMS Application-Layer Failover Example |
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| To run the example, simply type **mvn verify** from this directory. This example will always spawn and stop multiple brokers. |
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| ActiveMQ Artemis implements fully transparent **automatic** failover of connections from a live node to a backup node which requires no special coding. This is described in a different example and requires broker replication. |
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| However, ActiveMQ Artemis also supports **Application-Layer** failover which is useful in the case where replication is not enabled. |
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| With Application-Layer failover, it's up to the application to register a JMS ExceptionListener with ActiveMQ Artemis. This listener will then be called by ActiveMQ Artemis in the event that connection failure is detected. |
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| User code in the ExceptionListener can then recreate any JMS Connection, Session, etc on another node and the application can continue. |
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| Application-Layer failover is an alternative approach to High Availability (HA). |
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| Application-Layer failover differs from automatic failover in that some client side coding is required in order to implement this. Also, with Application-Layer failover, since the old Session object dies and a new is created, any uncommitted work in the old Session will be lost, and any unacknowledged messages might be redelivered. |
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| For more information on ActiveMQ Artemis failover and HA, and clustering in general, please see the clustering section of the user manual. |
