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 then subscribe to selected topics and receive the messages published to that topic by the publishers. According to this example, a user interested in sports can subscribe to the 'SportsNews' topic. This way, the user can continue to receive messages published to that topic.
The following 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.
Name: WSO2 Carbon - Event Feature
Identifier: org.wso2.carbon.event.feature.group
Name: WSO2 Carbon - Feature - Andes
Identifier: org.wso2.carbon.andes.feature.group
This feature can be removed or added to a different distribution if it is not already bundled as described in Working with Features.