Question

我正在使用Scala和Akka建模一个简单的P2P：

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：

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，如：

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)

我在Akka参考文档中遵循了Futures的文档。与Await.ready交换Await.result没有任何效果。日志显示上次注册成功。

我该如何解决这个问题？

Answer 1

您正在等待从Node actor返回的消息，但Node actor不会将消息发送回sender actorRef，因此s1 ? _register创建的Future [Any]将会永远不会得到回应，所以未来永远不会完整。您可以在Node sender ! something方法中添加receive来发送回复，我不确定something在这种情况下有什么意义。

Answer 2

stew是正确的，但你的网络演员有一些令人担忧的代码：

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")

为什么要创建一个新的ActorSystem，为什么要在该actor系统中创建顶级actor？

如果您需要访问演员的系统，可以简单地调用：

context.system

你应该避免创建“仅仅因为”的顶级演员，原因同样的方法是你不要把所有文件都放在那里弄乱文件系统的根。要创建子网络角色，请执行以下操作：

context.actorOf(...)

现在，只要您在同一系统中创建多个Network-actor，就会遇到问题，因为它会尝试创建同名的顶级actor。

Akka Actor使用TimeoutException“询问”和“等待”

2 个答案: