Publish/subscribe

Publish/subscribe is an asynchronous messaging paradigm, akin to message queueing.

In publish/subscribe communication. publishers post messages with specific “topics”, rather than sending messages to specific recipients. The messaging system then broadcasts the posted messages to all interested parties (subscribers).

Publish/subscribe communication is asynchronous by nature and gives even more loosely-coupled communication than one-to-one message queuing; the publishers do not even need to know who subscribes to their messages. Use publish/subscribe communication whenever scalability is an issue. The decoupled nature of publish/subscribe gives it superb scalability.

Publish/subscribe is a one-way communication. The publisher gets no response or other feedback (e.g. errors) to its messages. publishers need only concern themselves with creating the original message, and can then leave it to the messaging system to get the message to all the subscribers. To get feedback, may themselves subscribe to other topics (on which responses to their original messages may be posted).

Publisher

The process posting a message in publish/subscribe communication.

Subscriber

One of the processes receiving a message in publish/subscribe communication.