Introduction to Pub/Sub

Pub/Sub is a messaging system. What messaging systems do is receive messages from multiple systems and distribute them to multiple systems. The key here is multiple systems. A messaging system needs to be able to act as a bridge or middleware to many different systems.

The following diagram provides a high-level picture of Pub/Sub:

Figure 6.4 – Pub/Sub terminologies and flows

To understand how to use Pub/Sub, we need to understand the four main terminologies inside Pub/Sub, as follows:

• Publisher

  The entry point of Pub/Sub is the publisher. Pub/Sub uses the publisher to control incoming messages. Users can write code to publish messages from their applications using programming languages such as Java, Python, Go, C++, C#, Hypertext Preprocessor (PHP), and Ruby. Pub/Sub will store the messages in topics.

• Topic

  The central point of Pub/Sub is the topic. Pub/Sub stores messages in its internal storage. The sets of...