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
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Futures and blocking

Examples in this book should have shed the light into why blocking is sometimes considered an anti-pattern. Futures and asynchronous computations mainly exist to avoid blocking, but in some cases, we cannot live without it. It is, therefore, valid to ask how blocking interacts with futures.

There are two ways to block with futures. The first is waiting until a future is completed. The second is blocking from within an asynchronous computation. We will study both the topics in this section.

Awaiting futures

In rare situations, we cannot use callbacks or future combinators to avoid blocking. For example, the main thread that starts multiple asynchronous computations has to wait for these computations to finish. If an execution context uses daemon threads, as is the case with the global execution context, the main thread needs to block to prevent the JVM process from terminating.

In these exceptional circumstances, we use the ready and result methods on the Await object from...