Request-reply messaging through an IBM MQ link

When a JMS producer sends a message, it can provide a reply-to destination. The reply-to destination is a JMS destination defined using the producer's messaging provider. This style of messaging is known as request-reply, or request and response. Request-reply messages can be exchanged across the IBM MQ link as either point-to-point or publish/subscribe messages.

The following combinations are possible for request-reply exchanges:

1. Publication messages (for publish/subscribe messaging).
   1. Queue type reply-to destination.

   2. Topic type reply-to destination. This can be a permanent reply-to topic, which is defined to the publish/subscribe bridge on the IBM MQ link, or a temporary topic reply, where the topic name is assigned at runtime.

2. Point-to-point messages.
   1. Queue type reply-to destination.

   2. Topic type reply-to destination. The reply-to destination must be a permanent reply-to topic; we cannot have a temporary topic reply for a point-to-point request message.

When the producer is a WAS application that uses the default messaging provider, the reply-to destination is a service integration JMS destination that typically either points to a service integration queue, or comprises a topic string and a service integration topic space.

• If the reply-to destination is a service integration queue, it is normally a queue in the same bus as the WAS application, so that the WAS application can consume the reply message from that reply-to queue.

• If the reply-to destination is a topic and the consumer is an IBM MQ program, configure the publish/subscribe bridge to ensure that the reply message can be routed back to the service integration bus so that the WAS application can receive it. Note that although IBM MQ JMS applications can reply to a topic, most other IBM MQ applications cannot.

When the producer is an IBM MQ JMS application, the reply-to destination is an IBM MQ JMS destination that typically either points to an IBM MQ queue or is a topic string.

• If the reply-to destination is an IBM MQ queue, it is normally a queue in the queue manager, or shared queue in the queue-sharing group, that the IBM MQ application is using, so that the IBM MQ application can consume the reply message from that reply-to queue.

• If the reply-to destination is a topic and the consumer is a WAS application, configure the publish/subscribe bridge to ensure that the reply message can be routed back to IBM MQ so that the IBM MQ application can receive it.

Subtopics

• Reply-to queues for request-reply messaging through an IBM MQ link
  Reply-to queues indicate to a receiving application where a reply should be sent. Use reply-to queues for point-to-point request messages (queues) and for publish/subscribe request messages.
• Reply-to topics for request-reply messaging through an IBM MQ link
  WAS and IBM MQ JMS applications can publish messages to a topic space with a reply-to topic. Applications in the other network can receive the message, obtain the reply destination, and publish a message on the reply topic. Topic type replies cross the IBM MQ link through the publish/subscribe bridge.