Book Image

Hands-On Reactive Programming with Clojure - Second Edition

By : Konrad Szydlo, Leonardo Borges
Book Image

Hands-On Reactive Programming with Clojure - Second Edition

By: Konrad Szydlo, Leonardo Borges

Overview of this book

Reactive Programming is central to many concurrent systems, and can help make the process of developing highly concurrent, event-driven, and asynchronous applications simpler and less error-prone. This book will allow you to explore Reactive Programming in Clojure 1.9 and help you get to grips with some of its new features such as transducers, reader conditionals, additional string functions, direct linking, and socket servers. Hands-On Reactive Programming with Clojure starts by introducing you to Functional Reactive Programming (FRP) and its formulations, as well as showing you how it inspired Compositional Event Systems (CES). It then guides you in understanding Reactive Programming as well as learning how to develop your ability to work with time-varying values thanks to examples of reactive applications implemented in different frameworks. You'll also gain insight into some interesting Reactive design patterns such as the simple component, circuit breaker, request-response, and multiple-master replication. Finally, the book introduces microservices-based architecture in Clojure and closes with examples of unit testing frameworks. By the end of the book, you will have gained all the knowledge you need to create applications using different Reactive Programming approaches.
Table of Contents (15 chapters)

A minimal CES framework

Before we get started on the details, we should define what minimal means.

Let's start with the two main abstractions our framework will provide: behaviors and event streams.

If you can recall from Chapter 1, What is Reactive Programming?, behaviors represent continuous, time-varying values such as time or mouse position behavior. Event streams, on the other hand, represent discrete occurrences at a point in time, T, such as a key press.

Next, we should think about what kinds of operations we would like to support. Behaviors are fairly simple, so at the very least we need to do the following:

  1. Create new behaviors
  2. Retrieve the current value of a behavior
  3. Convert a behavior into an event stream

Event streams have more interesting logic at play and we should at least support these operations:

  • Push/deliver a value down the stream
  • Create a stream from...