Hello world with Akka

Let's install Akka. We add it as a dependency to our build.sbt file:

scalaVersion := "2.11.7"

libraryDependencies += "com.typesafe.akka" %% "akka-actor" % "2.4.0"

We can now import Akka as follows:

import akka.actor._

For our first foray into the world of actors, we will build an actor that echoes every message it receives. The code examples for this section are in a directory called chap09/hello_akka in the sample code provided with this book (https://github.com/pbugnion/s4ds):

// EchoActor.scala
import akka.actor._

class EchoActor extends Actor with ActorLogging {
  def receive = {
    case msg:String => 
      Thread.sleep(500)
      log.info(s"Received '$msg'") 
  }
}

Let's pick this example apart, starting with the constructor. Our actor class must extend Actor. We also add ActorLogging, a utility trait that adds the log attribute.

The Echo actor exposes a single method, receive. This is the actor's only way of communicating with the external world. To be useful...