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

Chapter 10.  Reactors


"Simplicity is prerequisite for reliability."

 --Edsger W. Dijkstra

Location-transparency, serializable event-handling, and non-blocking semantics of sends, make the actor model a powerful foundation for building distributed systems. However, the actor model has several important limitations, which only become apparent when building larger systems. First, actors cannot simultaneously contain multiple message entry points. All messages must arrive through the same receive block. Consequently, two different protocols cannot reuse the same message type, and must be aware of each other. The main example where we saw this was the Identify message, which required users to incorporate a unique token into the message. Second, actors cannot await specific combinations of messages. For example, it is cumbersome to simultaneously send a request message to two target actors, and proceed after both replies arrive. Third, the receive statement is not a first-class citizen. Event...