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
About the Reviewers
Customer Feedback

Rx schedulers

At the beginning of this chapter, we observed that different Observable objects emit events on different threads. A synchronous Observable object emits on the caller thread when the subscribe method gets invoked. The Observable.timer object emits events asynchronously on threads internally used by Rx. Similarly, events in Observable objects created from Future objects are emitted on ExecutionContext threads. What if we want to use an existing Observable object to create another Observable object bound to a specific thread?

To encapsulate the choice of the thread on which an Observable object should emit events, Rx defines a special class called Scheduler. A Scheduler class is similar to the Executor and ExecutionContext interfaces we saw in Chapter 3, Traditional Building Blocks of Concurrency. The Observable objects come with a combinator called observeOn. This combinator returns a new Observable object that emits events using the specified Scheduler class. In the following...