Publish/subscribe bridge on an IBM MQ link

A publish/subscribe bridge enables publish/subscribe messaging between WebSphere Application Server and IBM MQ through an IBM MQ link. The publish/subscribe bridge provides a connection between the publish/subscribe function of a service integration bus and the publish/subscribe function of an IBM MQ network.

When we use IBM MQ integrated publish/subscribe, the publish/subscribe bridge can connect as a subscriber or publisher to queue managers in the IBM MQ network:

• To act as a subscriber, the publish/subscribe bridge connects to an IBM MQ queue manager with a durable subscription to the relevant topic, and so receives messages when they are published on that topic. The publish/subscribe bridge then passes the messages to subscribers connected to a service integration bus in WAS. These subscribers might be applications running in WAS, or they might be bus clients running in Java Platform, Standard Edition (Java SE) or third party application servers.

• To act as a publisher, the publish/subscribe bridge subscribes to messages that applications have published to a service integration JMS topic destination in WAS. The publish/subscribe bridge then publishes the messages on the relevant topic in IBM MQ, and the IBM MQ queue manager distributes the messages to the subscribers in the IBM MQ network. Service integration can also send the messages to other subscribers connected to the service integration bus in WAS.

The publish/subscribe bridge acts in the same way if we use a queued publish/subscribe capability provided by a compatibility interface within IBM MQ v7, or by a separate message broker product. The publish/subscribe bridge attaches to the publish/subscribe broker as either a subscriber or a publisher, and receives messages from the message broker or publishes them to the message broker. The message broker distributes published messages to its subscribers in the IBM MQ network.

If communication between the two ends of the publish/subscribe bridge stops, messages are held until communication is reestablished by the system or by the administrator. If we are using a separate message broker product, the messages might be held on the input queues for the broker, if the broker is not available, or on the transmission queue for IBM MQ, if IBM MQ is not available.

The publish/subscribe bridge consists of the broker profiles and topic mappings that we have defined on the IBM MQ link:

• A broker profile defines a connection to a single IBM MQ queue manager or separate publish/subscribe broker. For more information about broker profiles, see Broker profile on an IBM MQ link.
• A topic mapping defines how messages on a particular topic flow between the two ends of the publish/subscribe bridge. For more information about topic mappings, see Topic mapping on an IBM MQ link.