Book Image

Scala Reactive Programming

By : Rambabu Posa
Book Image

Scala Reactive Programming

By: Rambabu Posa

Overview of this book

Reactive programming is a scalable, fast way to build applications, and one that helps us write code that is concise, clear, and readable. It can be used for many purposes such as GUIs, robotics, music, and others, and is central to many concurrent systems. This book will be your guide to getting started with Reactive programming in Scala. You will begin with the fundamental concepts of Reactive programming and gradually move on to working with asynchronous data streams. You will then start building an application using Akka Actors and extend it using the Play framework. You will also learn about reactive stream specifications, event sourcing techniques, and different methods to integrate Akka Streams into the Play Framework. This book will also take you one step forward by showing you the advantages of the Lagom framework while working with reactive microservices. You will also learn to scale applications using multi-node clusters and test, secure, and deploy your microservices to the cloud. By the end of the book, you will have gained the knowledge to build robust and distributed systems with Scala and Akka.
Table of Contents (16 chapters)

The Event Streaming Pattern

We have already discussed what an Event Stream is and its usage in Chapter 7, Working with Reactive Systems. Please refer to that chapter for more details.

Like a Messaging Queue, which is useful to store Messages, an Event Stream is useful to store a Set of Events. In other words, we can say that an Event Stream is a sequence of events.

As we know, in a Reactive System, each User Action is represented as an Event. These events are stored in a data store, as shown here:

Let's look at the Cassandra Data store for a better understanding. We also used the same data store to store our WF (Weather Forecasting) Reactive System events.

In Cassandra, we store our System's sequence of Events into an Event Stream. It is known as a Journal. We use Akka Persistence and Lagom Framework's Persistence API to store or retrieve our System's events...