This topic describes publishing and subscribing with a
broker in a WebSphere® MQ
network.
On a WebSphere MQ link
you can set up broker profiles to form a publish/subscribe bridge
that allows publication and subscription between
WebSphere Application Server and:
- IBM® WebSphere Business Integration Event Broker.
- IBM WebSphere Business Integration Message
Broker.
To identify the a supported version of WebSphere Business Integration brokers,
see the Supported hardware and software Web page http://www.ibm.com/support/docview.wss?rs=180&uid=swg27006921.
Publications can flow to and from the products listed above, even
simultaneously in both directions on the same topic.
- You define a broker profile for the named broker and its queue
manager, and topic mappings, and specify whether publishing or subscribing
or both. These definitions make up the publish/subscribe bridge. Read
more about the bridge at Publish/subscribe bridge.
- Broker profiles on the WebSphere MQ
link connect as regular subscribers and publishers to message brokers
in a WebSphere MQ network.
For example, for publications to move between WebSphere Application Server and WebSphere MQ, the broker profile
attaches as a durable subscriber to the relevant topic space and so
receives messages when they are published on that topic. The broker
profile then attaches as a publisher to, for example, WebSphere Business Integration Event Broker,
and republishes the message into the WebSphere MQ network where it can be received
by Event Broker subscribers. The reverse process applies when transferring
publications from the brokers in the WebSphere MQ network to WebSphere Application Server service integration.
Read more about broker profiles at Broker profile.
- Publications flow between the two sides of the publish/subscribe
bridge according to the topic mappings you define. The topic name
hierarchy on the topic space must be the same as the topic name hierarchy
on the message broker in the WebSphere MQ
network. If a topic mapping is bidirectional, a message is safeguarded
from being continually republished on alternating sides of the publish/subscribe
bridge. Read more about the topic mappings at Topic mapping.
- Wild cards differ between WebSphere Application Server service integration
and a WebSphere MQ network.
To find about more about wild card mapping see Wild cards in topic mapping.
- Messages published by a WebSphere Application Server service integration
JMS client may be transferred to a message broker in a WebSphere MQ network if an appropriate
topic mapping has been created. This is presented to the WebSphere MQ network as only the topic
name, for example, "sports/football". A suitably configured WebSphere MQ JMS application
can use this information to publish further information to the same
topic, but the original WebSphere Application Server JMS application
will receive these messages only if appropriate topic mapping has
been configured.
- Message headers and contents are mapped in the same way for both
point-to-point messages and publish/subscribe messages. To find out
more about the mapping of messages see Mapping messages between a WebSphere service integration bus and WebSphere MQ.
- If communication between the two sides of the publish/subscribe
bridge fails, messages are held on each side until communication is
reestablished. If a broker in the WebSphere MQ
network fails it will publish no new messages. Messages published
by WebSphere Application Server applications
are transferred to WebSphere MQ
and build up on broker input queues until the broker resumes processing.
If WebSphere MQ fails,
the message broker is unable to publish messages. Messages published
by WebSphere Application Server applications
cannot be transferred to WebSphere MQ
so they are stored on the application server until server channels
can be restarted.