Book Image

Learning Concurrent Programming in Scala - Second Edition

By : Aleksandar Prokopec
Book Image

Learning Concurrent Programming in Scala - Second Edition

By: Aleksandar Prokopec

Overview of this book

Scala is a modern, multiparadigm programming language designed to express common programming patterns in a concise, elegant, and type-safe way. Scala smoothly integrates the features of object-oriented and functional languages. In this second edition, you will find updated coverage of the Scala 2.12 platform. The Scala 2.12 series targets Java 8 and requires it for execution. The book starts by introducing you to the foundations of concurrent programming on the JVM, outlining the basics of the Java Memory Model, and then shows some of the classic building blocks of concurrency, such as the atomic variables, thread pools, and concurrent data structures, along with the caveats of traditional concurrency. The book then walks you through different high-level concurrency abstractions, each tailored toward a specific class of programming tasks, while touching on the latest advancements of async programming capabilities of Scala. It also covers some useful patterns and idioms to use with the techniques described. Finally, the book presents an overview of when to use which concurrency library and demonstrates how they all work together, and then presents new exciting approaches to building concurrent and distributed systems. Who this book is written for If you are a Scala programmer with no prior knowledge of concurrent programming, or seeking to broaden your existing knowledge about concurrency, this book is for you. Basic knowledge of the Scala programming language will be helpful.
Table of Contents (19 chapters)
Learning Concurrent Programming in Scala - Second Edition
About the Author
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As we learned previously, event streams always propagate events on a single thread. This is useful from the standpoint of program comprehension, but we still need a way to express concurrency in our programs. In this section, we will see how to achieve concurrency by using entities called reactors.

A reactor is the basic unit of concurrency. While actors receive messages, we will adopt the terminology in which reactors receive events, in order to disambiguate. However, while an actor a in particular state has only a single point where it can receive a message, namely, the receive statement, a reactor can receive an event from many different sources at any time. Despite this flexibility, one reactor will always process, at most, one event at any time. We say that events received by a reactor are serialized, similar to how messages received by an actor are serialized.

To be able to create new reactors, we need a ReactorSystem object, which tracks reactors in a single machine:

val system...