Akka演员“问”和“等待”与TimeoutException [英] Akka Actor "ask" and "Await" with TimeoutException

问题描述

我正在用Scala和Akka建模一个简单的P2P：

I'm modeling a simple P2P with Scala and Akka:

class Node() extends Peer with Actor {

  var peers: List[ActorRef] = List()

  def receive = {
    case _register(peer: ActorRef, p: Option[Int]) => {
      println("registering [" + peer + "] for [" + this + "]")
      peers = peer :: peers
    }
  }

}

sealed case class _register(val peer: ActorRef, var p: Option[Int] = None)

然后是一个简单的网络：

and then a simple network:

class Network() extends Actor {

  def this(name: String) = {

    this()

    val system = ActorSystem(name)

    val s1 = system.actorOf(Props(new Node()), name = "s1")
    val s2 = system.actorOf(Props(new Node()), name = "s2")

    val c1 = system.actorOf(Props(new Node()), name = "c1")
    val c2 = system.actorOf(Props(new Node()), name = "c2")
    val c3 = system.actorOf(Props(new Node()), name = "c3")
    val c4 = system.actorOf(Props(new Node()), name = "c4")

    implicit val timeout = Timeout(5 second)

    s1 ? _register(c1)
    s1 ? _register(c2)
    s1 ? _register(c3)
    val lastRegistered = s2 ? _register(c4)
    Await.ready(lastRegistered, timeout.duration)

    println("initialized nodes")
  }
}

我得到的输出总是 ，例如：

The output that I'm getting is always like:

registering [Actor[akka://p2p/user/c1]] for [nl.cwi.crisp.examples.p2p.scala.Node@14b5f4a]
registering [Actor[akka://p2p/user/c2]] for [nl.cwi.crisp.examples.p2p.scala.Node@14b5f4a]
registering [Actor[akka://p2p/user/c3]] for [nl.cwi.crisp.examples.p2p.scala.Node@14b5f4a]
registering [Actor[akka://p2p/user/c4]] for [nl.cwi.crisp.examples.p2p.scala.Node@13c0b53]
[ERROR] [04/10/2012 22:07:04.34] [main-akka.actor.default-dispatcher-1] [akka://main/user/p2p] error while creating actor
java.util.concurrent.TimeoutException: Futures timed out after [5000] milliseconds
    at akka.dispatch.DefaultPromise.ready(Future.scala:834)
    at akka.dispatch.DefaultPromise.ready(Future.scala:811)
    at akka.dispatch.Await$.ready(Future.scala:64)
    at nl.cwi.crisp.examples.p2p.scala.Network.<init>(Node.scala:136)
    at nl.cwi.crisp.examples.p2p.scala.Main$$anonfun$11.apply(Node.scala:164)
    at nl.cwi.crisp.examples.p2p.scala.Main$$anonfun$11.apply(Node.scala:164)
    at akka.actor.ActorCell.newActor(ActorCell.scala:488)
    at akka.actor.ActorCell.create$1(ActorCell.scala:506)
    at akka.actor.ActorCell.systemInvoke(ActorCell.scala:591)
    at akka.dispatch.Mailbox.processAllSystemMessages(Mailbox.scala:191)
    at akka.dispatch.Mailbox.run(Mailbox.scala:160)
    at akka.dispatch.ForkJoinExecutorConfigurator$MailboxExecutionTask.exec(AbstractDispatcher.scala:505)
    at akka.jsr166y.ForkJoinTask.doExec(ForkJoinTask.java:259)
    at akka.jsr166y.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:997)
    at akka.jsr166y.ForkJoinPool.runWorker(ForkJoinPool.java:1495)
    at akka.jsr166y.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:104)

我遵循了未来。将 Await.ready 与 Await.result 交换没有任何效果。日志显示上一次注册已成功。

I have followed the documentation of Futures on Akka reference documentation. Exchanging Await.ready with Await.result does not have any effect. The log shows that the last registration has been successful.

我该如何解决？

推荐答案

您正在等待消息将从Node actor返回，但是Node actor不会将消息发送回 sender actorRef，因此<$ c $创建的Future [Any] c> s1？ _register 将永远不会收到响应，因此Future将永远不会完成。您可以添加 sender！节点接收方法中的某事发送响应，我不确定某事在这种情况下很有意义。

You are waiting for a message to be returned from the Node actor, but the Node actor does not send a message back to the sender actorRef, so the Future[Any] created by s1 ? _register will never receive a response, so the Future will never be complete. You could add sender ! something from inside the Node receive method to send a response, I'm not sure what something makes sense in this case.

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