strobe/BackendApp.scala

## application.conf
akka {
  loglevel = INFO

  log-dead-letters                 = off
  log-dead-letters-during-shutdown = off

  # /// Clusterring. /// #
  # For clustering the following configuration needs to be enabled
  actor {
    provider = "akka.cluster.ClusterActorRefProvider"

    # //#config-router-lookup
    deployment {
      /spray-service/routerActor/workerRouter {
        router = round-robin-group
        nr-of-instances = 10
        routees.paths = ["/user/backend"]
        cluster {
          enabled = on
          allow-local-routees = on
        }
      }
    }
    # //#config-router-lookup
  }

  remote {
    log-remote-lifecycle-events = off
    netty.tcp {
      hostname = "127.0.0.1"
      port = 0
    }
  }

  cluster {
    # list of seed nodes which may be started on same JVM (just few Akka Systems)
    # and on different JVMs (as well on different nodes)
    seed-nodes = [
      "akka.tcp://ClusterSystem@127.0.0.1:2551",
      "akka.tcp://ClusterSystem@127.0.0.1:2552"]

    # this setting is used for case when nodes is fail,
    # after that timeout node will be removed from cluster
    auto-down-unreachable-after = 10s
  }
  #  remote.netty.tcp.maximum-frame-size = 384000b
  # /// end /// #

}

## BackendApp.scala
object BackendApp {
  def main(args: Array[String]): Unit = {
    // Override the configuration of the port when specified as program argument
    val port = if (args.isEmpty) "0" else args(0)
    val config = ConfigFactory.parseString(s"akka.remote.netty.tcp.port=$port").
      withFallback(ConfigFactory.parseString("akka.cluster.roles = [backend]")).
      withFallback(ConfigFactory.load())

    val system = ActorSystem("ClusterSystem", config)
    system.actorOf(Props[BackendWorkerActor], name = "backend")
  }
}

## BackendsRouterActor.scala
class BackendsRouterActor extends Actor with ActorLogging {
  // router which defined in config
  val workersRouter = context.actorOf(FromConfig.props(Props.empty), name = "workerRouter")

  implicit def executionContext: ExecutionContextExecutor = context.dispatcher

  def receive = {
    case ToRouter(message: BackendMessage) => {
      workersRouter ! ToBackEnd(message, sender())
    }

    case BackToRouter(message: FrontendMessage, origin: ActorRef) => {
      log.info("BackToRouter recevied to BackendsRouterActor ")
      origin ! BackToOrigin(message)
    }
  }
}

## BackendsWorkerActor.scala
class BackendWorkerActor extends Actor with ActorLogging {

  val cluster = Cluster(context.system)

  implicit def executionContext: ExecutionContextExecutor = context.dispatcher

  def receive = {
    case ToBackEnd(message: BackendMessage, origin: ActorRef) => {
      message match {
        case TestAsk(ctx: RequestContext) => {
          log.info("ToBackEndTestAskResponse recevied to BackendWorkerActor ")
          sender ! BackToRouter(TestAskResponse("job result"), origin)
        }
        case SimpleStringStream(ctx: RequestContext) => {
          val stream: Stream[String] = new Streamer(context).simpleStringStream
          sender ! BackToRouter(SimpleStringStreamResponse(stream), origin)
        }
      }

    }
  }

}

## ClusterApp.scala
object ClusterApp {

  def main(args: Array[String]): Unit = {
    FrontendSprayApp.main(Seq("2551").toArray)
    BackendApp.main(Seq("2552").toArray)
    BackendApp.main(Array.empty)
    BackendApp.main(Array.empty)
  }

}

## FrontendApp.scala
object FrontendSprayApp {
  def main(args: Array[String]): Unit = {
    // Override the configuration of the port when specified as program argument
    val port = if (args.isEmpty) "0" else args(0)
    val config = ConfigFactory.parseString(s"akka.remote.netty.tcp.port=$port").
      withFallback(ConfigFactory.parseString("akka.cluster.roles = [frontend]")).
      withFallback(ConfigFactory.load())

    implicit val system = ActorSystem("ClusterSystem", config)

    // server actor initialization
    val service = system.actorOf(Props[FrontendServerActor], "spray-service")

    // http initialization
    IO(Http) ! Http.Bind(service, interface = "localhost", port = 8050)

  }
}

## FrontendServerActor.scala
class FrontendServerActor extends Actor with ChunksTestService with ActorLogging {

  def actorRefFactory = context

  def receive = {
    runRoute(apiRoute)
  }
}

trait ChunksTestService extends HttpService {

  // These implicit values allow us to use futures
  // in this trait.
  implicit def executionContext = actorRefFactory.dispatcher
  implicit val timeout = Timeout(5.seconds)

  // Our worker Actor handles the work of the request.
  val router = actorRefFactory.actorOf(Props[BackendsRouterActor], "routerActor")

  val apiRoute =
    path("ping") {
      get {
        complete("PONG")
      }
    } ~
    path("html_stream") {
      get {
        respondWithMediaType(`text/html`) {
          ctx => doSimpleStringStream(ctx)
        }
      }
    }


  def doTestAskResponse(ctx: RequestContext) = {
    actorRefFactory.actorOf {
      Props {
        new Actor with ActorLogging {
          // To set an initial possible delay
          context.setReceiveTimeout(600 millis)

          override def preStart = {
            router ! ToRouter(TestAsk(ctx))
          }

          def receive = {
            case BackToOrigin(message: FrontendMessage) =>
              message match {
                case TestAskResponse(text: String) =>
                  ctx.responder ! HttpResponse(StatusCodes.OK, text)
              }

            case ReceiveTimeout =>
              // To turn it off
              ctx.responder ! HttpResponse(StatusCodes.NetworkConnectTimeout,
                "backend worker doesn't produced result in expected time!")
          }
        }
      }
    }
  }

  def doSimpleStringStream(ctx: RequestContext) = {
    actorRefFactory.actorOf {
      Props {
        new Actor with ActorLogging {
          override def preStart = {
            router ! ToRouter(SimpleStringStream(ctx))
          }

          def receive = {
            case BackToOrigin(message: FrontendMessage) =>
              message match {
                case SimpleStringStreamResponse(stream: Stream[String]) =>
                  ctx.responder ! complete(stream)
              }

            case ReceiveTimeout =>
              ctx.responder ! HttpResponse(StatusCodes.NetworkConnectTimeout,
                "backend worker doesn't produced result in expected time!")
          }
        }
      }
    }
  }
}


## Messages.scala
// possible messages types
object BackendMessages {
  //
  case class ToRouter(message: BackendMessage)
  case class ToBackEnd(message: BackendMessage, originRef: ActorRef)
  //
  case class BackToRouter(message: FrontendMessage, originRef: ActorRef)
  case class BackToOrigin(message: FrontendMessage)
  //
}

// messages which may send to backend
abstract class BackendMessage
case class TestAsk(ctx: RequestContext) extends BackendMessage
case class SimpleStringStream(ctx: RequestContext) extends BackendMessage

// messages which may send to frontend
abstract class FrontendMessage
case class TestAskResponse(text: String) extends FrontendMessage
case class SimpleStringStreamResponse(stream: Stream[String]) extends FrontendMessage

## Streamer.scala
class Streamer(actorRefFactory: ActorContext) (implicit ec: ExecutionContext)  {
  lazy val streamStart = " " * 2048 + "<html><body><h2>A streaming response</h2><p>(for 15 seconds)<ul>"
  lazy val streamEnd = "</ul><p>Finished.</p></body></html>"

  def simpleStringStream: Stream[String] = {
    val secondStream = Stream.continually {
      // CAUTION: we block here to delay the stream generation for you to
      // be able to follow it in your browser,
      // this is only done for the purpose of this demo, blocking in actor
      // code should otherwise be avoided
      //      Thread.sleep(500)
      "<li>" + DateTime.now.toIsoDateTimeString + "</li>"
    }
    streamStart #:: secondStream.take(15) #::: streamEnd #:: Stream.empty
  }

}
	akka {
	loglevel = INFO

	log-dead-letters = off
	log-dead-letters-during-shutdown = off

	# /// Clusterring. /// #
	# For clustering the following configuration needs to be enabled
	actor {
	provider = "akka.cluster.ClusterActorRefProvider"

	# //#config-router-lookup
	deployment {
	/spray-service/routerActor/workerRouter {
	router = round-robin-group
	nr-of-instances = 10
	routees.paths = ["/user/backend"]
	cluster {
	enabled = on
	allow-local-routees = on
	}
	}
	}
	# //#config-router-lookup
	}

	remote {
	log-remote-lifecycle-events = off
	netty.tcp {
	hostname = "127.0.0.1"
	port = 0
	}
	}

	cluster {
	# list of seed nodes which may be started on same JVM (just few Akka Systems)
	# and on different JVMs (as well on different nodes)
	seed-nodes = [
	"akka.tcp://ClusterSystem@127.0.0.1:2551",
	"akka.tcp://ClusterSystem@127.0.0.1:2552"]

	# this setting is used for case when nodes is fail,
	# after that timeout node will be removed from cluster
	auto-down-unreachable-after = 10s
	}
	# remote.netty.tcp.maximum-frame-size = 384000b
	# /// end /// #

	}
	object BackendApp {
	def main(args: Array[String]): Unit = {
	// Override the configuration of the port when specified as program argument
	val port = if (args.isEmpty) "0" else args(0)
	val config = ConfigFactory.parseString(s"akka.remote.netty.tcp.port=$port").
	withFallback(ConfigFactory.parseString("akka.cluster.roles = [backend]")).
	withFallback(ConfigFactory.load())

	val system = ActorSystem("ClusterSystem", config)
	system.actorOf(Props[BackendWorkerActor], name = "backend")
	}
	}
	class BackendsRouterActor extends Actor with ActorLogging {
	// router which defined in config
	val workersRouter = context.actorOf(FromConfig.props(Props.empty), name = "workerRouter")

	implicit def executionContext: ExecutionContextExecutor = context.dispatcher

	def receive = {
	case ToRouter(message: BackendMessage) => {
	workersRouter ! ToBackEnd(message, sender())
	}

	case BackToRouter(message: FrontendMessage, origin: ActorRef) => {
	log.info("BackToRouter recevied to BackendsRouterActor ")
	origin ! BackToOrigin(message)
	}
	}
	}
	class BackendWorkerActor extends Actor with ActorLogging {

	val cluster = Cluster(context.system)

	implicit def executionContext: ExecutionContextExecutor = context.dispatcher

	def receive = {
	case ToBackEnd(message: BackendMessage, origin: ActorRef) => {
	message match {
	case TestAsk(ctx: RequestContext) => {
	log.info("ToBackEndTestAskResponse recevied to BackendWorkerActor ")
	sender ! BackToRouter(TestAskResponse("job result"), origin)
	}
	case SimpleStringStream(ctx: RequestContext) => {
	val stream: Stream[String] = new Streamer(context).simpleStringStream
	sender ! BackToRouter(SimpleStringStreamResponse(stream), origin)
	}
	}

	}
	}

	}
	object ClusterApp {

	def main(args: Array[String]): Unit = {
	FrontendSprayApp.main(Seq("2551").toArray)
	BackendApp.main(Seq("2552").toArray)
	BackendApp.main(Array.empty)
	BackendApp.main(Array.empty)
	}

	}
	object FrontendSprayApp {
	def main(args: Array[String]): Unit = {
	// Override the configuration of the port when specified as program argument
	val port = if (args.isEmpty) "0" else args(0)
	val config = ConfigFactory.parseString(s"akka.remote.netty.tcp.port=$port").
	withFallback(ConfigFactory.parseString("akka.cluster.roles = [frontend]")).
	withFallback(ConfigFactory.load())

	implicit val system = ActorSystem("ClusterSystem", config)

	// server actor initialization
	val service = system.actorOf(Props[FrontendServerActor], "spray-service")

	// http initialization
	IO(Http) ! Http.Bind(service, interface = "localhost", port = 8050)

	}
	}
	class FrontendServerActor extends Actor with ChunksTestService with ActorLogging {

	def actorRefFactory = context

	def receive = {
	runRoute(apiRoute)
	}
	}

	trait ChunksTestService extends HttpService {

	// These implicit values allow us to use futures
	// in this trait.
	implicit def executionContext = actorRefFactory.dispatcher
	implicit val timeout = Timeout(5.seconds)

	// Our worker Actor handles the work of the request.
	val router = actorRefFactory.actorOf(Props[BackendsRouterActor], "routerActor")

	val apiRoute =
	path("ping") {
	get {
	complete("PONG")
	}
	} ~
	path("html_stream") {
	get {
	respondWithMediaType(`text/html`) {
	ctx => doSimpleStringStream(ctx)
	}
	}
	}


	def doTestAskResponse(ctx: RequestContext) = {
	actorRefFactory.actorOf {
	Props {
	new Actor with ActorLogging {
	// To set an initial possible delay
	context.setReceiveTimeout(600 millis)

	override def preStart = {
	router ! ToRouter(TestAsk(ctx))
	}

	def receive = {
	case BackToOrigin(message: FrontendMessage) =>
	message match {
	case TestAskResponse(text: String) =>
	ctx.responder ! HttpResponse(StatusCodes.OK, text)
	}

	case ReceiveTimeout =>
	// To turn it off
	ctx.responder ! HttpResponse(StatusCodes.NetworkConnectTimeout,
	"backend worker doesn't produced result in expected time!")
	}
	}
	}
	}
	}

	def doSimpleStringStream(ctx: RequestContext) = {
	actorRefFactory.actorOf {
	Props {
	new Actor with ActorLogging {
	override def preStart = {
	router ! ToRouter(SimpleStringStream(ctx))
	}

	def receive = {
	case BackToOrigin(message: FrontendMessage) =>
	message match {
	case SimpleStringStreamResponse(stream: Stream[String]) =>
	ctx.responder ! complete(stream)
	}

	case ReceiveTimeout =>
	ctx.responder ! HttpResponse(StatusCodes.NetworkConnectTimeout,
	"backend worker doesn't produced result in expected time!")
	}
	}
	}
	}
	}
	}
	// possible messages types
	object BackendMessages {
	//
	case class ToRouter(message: BackendMessage)
	case class ToBackEnd(message: BackendMessage, originRef: ActorRef)
	//
	case class BackToRouter(message: FrontendMessage, originRef: ActorRef)
	case class BackToOrigin(message: FrontendMessage)
	//
	}

	// messages which may send to backend
	abstract class BackendMessage
	case class TestAsk(ctx: RequestContext) extends BackendMessage
	case class SimpleStringStream(ctx: RequestContext) extends BackendMessage

	// messages which may send to frontend
	abstract class FrontendMessage
	case class TestAskResponse(text: String) extends FrontendMessage
	case class SimpleStringStreamResponse(stream: Stream[String]) extends FrontendMessage
	class Streamer(actorRefFactory: ActorContext) (implicit ec: ExecutionContext) {
	lazy val streamStart = " " * 2048 + "<html><body><h2>A streaming response</h2><p>(for 15 seconds)<ul>"
	lazy val streamEnd = "</ul><p>Finished.</p></body></html>"

	def simpleStringStream: Stream[String] = {
	val secondStream = Stream.continually {
	// CAUTION: we block here to delay the stream generation for you to
	// be able to follow it in your browser,
	// this is only done for the purpose of this demo, blocking in actor
	// code should otherwise be avoided
	// Thread.sleep(500)
	"<li>" + DateTime.now.toIsoDateTimeString + "</li>"
	}
	streamStart #:: secondStream.take(15) #::: streamEnd #:: Stream.empty
	}

	}