Scala Cookbook

Introduction

In Scala you can still use Java threads, but the Actor model is the preferred approach for concurrency. The Actor model is at a much higher level of abstraction than threads, and once you understand the model, it lets you focus on solving the problem at hand, rather than worrying about the low-level problems of threads, locks, and shared data.

Although earlier versions of Scala included its original Actors library, Scala 2.10.0 began the official transition to the Akka actor library from Typesafe, which is more robust than the original library. Scala 2.10.1 then deprecated the original scala.actors library.

In general, actors give you the benefit of offering a high level of abstraction for achieving concurrency and parallelism. Beyond that, the Akka actor library adds these additional benefits:

• Lightweight, event-driven processes. The documentation states that there can be approximately 2.7 million actors per gigabyte of RAM.

• Fault tolerance. Akka actors can be used to create “self-healing systems.” (The Akka “team blog” is located at http://letitcrash.com/.)

• Location transparency. Akka actors can span multiple JVMs and servers; they’re designed to work in a distributed environment using pure message passing.

A “high level of abstraction” can also be read as “ease of use.” It doesn’t take very long to understand the Actor model, and once you do, you’ll be able to write complex, concurrent applications much more easily than you can with the basic Java libraries. I wrote a ...