Introduction

Messaging provides an synchronous communication protocol, as compared with the request response model such as Remote Procedure Call (RPC). In the world of messaging, there are broadly 2 patterns as described below.

Publish Subscribe messaging pattern

Publish Subscribe is a messaging pattern where senders of messages (aka Publisher), do not send the messages directly to the receivers (aka Subscriber). Instead, the Publisher will publish the messages to “Topic” on a messaging broker without knowledge of the Subscriber. Similarly, Subscribers express interest in one or more “Topics” only receive messages that are of interest, without any knowledge of the Publisher.

 The Publisher and the Subscribers never know the existence of one another. They communicate via a message broker such as Anypoint MQ.

 The Publish Subscribe model allows messages to be broadcast to different subscribers asynchronously. Additional subscribers can be added to the system in the future to consume the messages without changes or impact to existing publishers or subscribers.

 The Publish Subscribe pattern is illustrated in the diagram below: