High Availability

Message Queue 4.1 introduces high availability clusters, which provide data availability as well as service availability. If a client loses its connection to a high availability broker, it is automatically reconnected to another broker in a cluster. The broker that provides the new connection takes over the failed broker's persistent data and state, and continues to provide uninterrupted service to the failed broker's clients. You can run high availability brokers over a secure connection.

High availability brokers require the use of a highly available database (HADB). If you do not have such a database or if data availability is not important to you, you can continue to use conventional clusters, which offer automatic reconnection and service availability.

Configuring high availability brokers is simple: you specify the following kinds of broker properties for each broker in the cluster.

• Cluster membership properties, which specify that the broker is part of a high availability cluster, the id of the cluster, and the id of the broker.

• Highly available database (HADB) properties, which specify the model for persistent messages (JDBC), the name of the HADB vendor, and vendor-specific configuration properties for the database.

• Failure detection and takeover properties, which specify how broker failure should be detected and handled.

To use this feature, you must do the following:

1. Install a highly available database.

2. Install the JDBC driver's .jar file.

3. Create the database schema for the highly available persistent store.

4. Set those properties that are related to high availability for each broker in the cluster.

5. Start each broker in the cluster.

For a conceptual discussion of high availability and how it compares to conventional clusters, see Chapter 4, Broker Clusters, in Sun Java System Message Queue 4.1 Technical Overview. For procedural and reference information about high availability, see Chapter 8, Broker Clusters, in Sun Java System Message Queue 4.1 Administration Guide and Cluster Configuration Properties in Sun Java System Message Queue 4.1 Administration Guide.

If you were using an HADB database with Message Queue version 4.0 and want to use a high availability cluster, you can use the dbmgr utility to upgrade to a shared HADB store. See Broker Clusters for more information.