Chapter 5. Publish-and-Subscribe Messaging
This chapter focuses on the publish-and-subscribe (pub/sub) messaging model. This messaging model is used when you need to broadcast an event or message to many message consumers. Unlike the point-to-point messaging model discussed in Chapter 4, all message consumers (called subscribers) listening on the topic will receive the message.
In this chapter, we will describe the publish-and-subscribe model
through the use of a typical broadcast messaging scenario where a mortgage
lender publishes its latest mortgage rates for a 30-year fixed mortgage to
various borrowers in the hope of attracting one of the borrowers to apply for
a mortgage loan. The TLender class will
publish a new mortgage rate through a topic, and the TBorrower class will subscribe to the topic and
make a decision on whether or not it is a good rate.
We have mentioned several new terms already in this chapter: topic, subscriber, and publish. Before moving on to the code example, we will first describe the main characteristics and nomenclature of the publish-and-subscribe model and discuss some of the typical use cases for this model.
Publish-and-Subscribe Overview
The publish-and-subscribe model is more commonly referred to as the pub/sub model. In this model, the message producer is called a publisher and the message consumer a subscriber. Messages are published to a topic as opposed to being sent to a queue, as in the point-to-point model. The most important characteristics ...