Akka/Scala example source code file (ReadBackPressure.scala)

This example Akka source code file (ReadBackPressure.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

ack, actor, actorref, akka, event, io, resumeaccepting, resumereading, test, testing, testkit, testprobe, unit, util, write

The ReadBackPressure.scala Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */
package docs.io

import akka.actor.{ ActorRef, ActorLogging, Props, Actor, ActorSystem }
import akka.io.Tcp._
import akka.io.{ Tcp, IO }
import java.net.InetSocketAddress
import akka.testkit.{ ImplicitSender, TestProbe, AkkaSpec }
import akka.util.ByteString

object PullReadingExample {

  class Listener(monitor: ActorRef) extends Actor {

    import context.system

    override def preStart: Unit =
      //#pull-mode-bind
      IO(Tcp) ! Bind(self, new InetSocketAddress("localhost", 0), pullMode = true)
    //#pull-mode-bind

    def receive = {
      //#pull-accepting
      case Bound(localAddress) =>
        // Accept connections one by one
        sender() ! ResumeAccepting(batchSize = 1)
        context.become(listening(sender()))
        //#pull-accepting
        monitor ! localAddress
    }

    //#pull-accepting-cont
    def listening(listener: ActorRef): Receive = {
      case Connected(remote, local) =>
        val handler = context.actorOf(Props(classOf[PullEcho], sender()))
        sender() ! Register(handler, keepOpenOnPeerClosed = true)
        listener ! ResumeAccepting(batchSize = 1)
    }
    //#pull-accepting-cont

  }

  case object Ack extends Event

  class PullEcho(connection: ActorRef) extends Actor {

    //#pull-reading-echo
    override def preStart: Unit = connection ! ResumeReading

    def receive = {
      case Received(data) => connection ! Write(data, Ack)
      case Ack            => connection ! ResumeReading
    }
    //#pull-reading-echo
  }

}

class PullReadingSpec extends AkkaSpec with ImplicitSender {

  "demonstrate pull reading" in {
    val probe = TestProbe()
    system.actorOf(Props(classOf[PullReadingExample.Listener], probe.ref), "server")
    val listenAddress = probe.expectMsgType[InetSocketAddress]

    //#pull-mode-connect
    IO(Tcp) ! Connect(listenAddress, pullMode = true)
    //#pull-mode-connect
    expectMsgType[Connected]
    val connection = lastSender

    val client = TestProbe()
    client.send(connection, Register(client.ref))
    client.send(connection, Write(ByteString("hello")))
    client.send(connection, ResumeReading)
    client.expectMsg(Received(ByteString("hello")))

    system.shutdown()
    system.awaitTermination
  }
}