Parallel Downloader per hostname

Downloader.scala

package actors

import java.net.URI

import akka.actor.{Actor, ActorRef, Props}
import akka.pattern.{ask, pipe}
import akka.util.Timeout
import skinny.http.HTTP

import scala.collection.mutable
import scala.concurrent.ExecutionContext
import scala.concurrent.duration._

class Downloader(ec: ExecutionContext) extends Actor {
  implicit val timeout = Timeout(30.second)
  implicit val _ec: ExecutionContext = ec
  val downloadActor: mutable.Map[String, ActorRef] = mutable.Map()

  override def receive = {
    case method: Method =>
      val host = new URI(method.url).getHost
      val actor = downloadActor.getOrElseUpdate(host, createActor(host))
      println("receive")
      (actor ? method).pipeTo(sender())
  }

  def createActor(host: String): ActorRef =
    context.actorOf(Props(new DownloadHost(host)))
}

class DownloadHost(host: String) extends Actor {
  import Method._

  val http = new HTTP
  http.defaultConnectTimeoutMillis = 30.seconds.toMillis.toInt

  override def receive = {
    case Get(url: String) =>
      sender ! http.get(url)
  }
}

sealed abstract class Method {
  def url: String
}

object Method {
  case class Get(url: String) extends Method
}