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In messaging systems, message routing is done on the basis of a concept called topics. When a particular user wants to publish a message to a particular sector, he creates a topic typically with a name relevant to the messages to be published. For example, to publish messages related to sports, a topic by the name of 'SportsNews' can be created and messages related to sports news can be published under that topic.
Users can look up the different topics in the topic tree, then subscribe to selected topics and receive the messages which are published to that topic by the publishers. According to the this example above, a user is interested on in sports can subscribed subscribe to the topic 'SportsNews' topic. This way, the user can continue to receive messages published to that topic.
The message publish and subscribe flow of topics is depicted in the diagram belowfollowing flow diagram depicts how messages are published to topics and how users subscribe:
The topics and subscriptions management capability in WSO2 Message Broker is provided by the following feature in the WSO2 feature repository.
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This feature can be removed or added to a different distribution if it is not already bundled as described in Working with Features.