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/software/webservers/appserv/doc/latest/prereq.html.
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 of messages flowing through the WebSphere MQ link.
- 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.