Question

我正在使用Akka Cluster（版本2.4.10），其中几个节点被指定用于＆＃34;前端＆＃34;角色和其他几个人作为＆＃34;工人＆＃34;。工人在远程机器上。传入的工作由前端角色通过循环路由分配给工作人员。问题是回复工人＆＃34;回到前端演员。我可以看到这项工作正在由工人完成。但工人发送到前端的消息并没有达到并最终成为死信。我在日志中看到以下错误。

[Cluster-akka.actor.default-dispatcher-21] [akka://Cluster/deadLetters] Message [scala.collection.immutable.$colon$colon] from Actor[akka://Cluster/user] to Actor[akka://Cluster/deadLetters] was not delivered. [6] dead letters encountered.

我见过this，我的代码也是如此。我也看过this，但建议的解决方案不适用于这种情况，因为我不知道前面的路由。它来自配置，它可以改变。循环路由器配置如下。

akka.actor.deployment {
  /frontEnd/hm = {
    router = round-robin-group
    nr-of-instances = 5
    routees.paths = ["/user/hmWorker"]
    cluster {
      enabled = on
      use-role = backend
      allow-local-routees = on
    }
  }
}

路由器在前端actor中实例化，如下所示。

val router = context.actorOf(FromConfig.props(), name = "hm")
val controller = context.actorOf(Props(classOf[Controller], router))

控制器和工人代码在下面。

// Node 1 : Controller routes requests using round-robin
class Controller(router: ActorRef) extends Actor {

    val list = List("a", "b") // Assume this is a big list

    val groups = list.grouped(500)

    override def receive: Actor.Receive = {
      val futures = groups.map(grp => (router ? Message(grp)).mapTo[List[String]]))
      val future = Future.sequence(futures).map(_.flatten)
      val result = Await.result(future, 50 seconds)
      println(s"Result is $result")
    }
}

// Node 2
class Worker extends Actor {

    override def receive: Actor.Receive = {
      case Message(lst) =>
            val future: Future[List[String]] = // Do Something asynchronous
            future onComplete {
                case Success(r) => sender.!(r)(context.parent) // This message is not delivered to Controller actor.
                case Failure(th) => // Error handling
            }
    }
}

请告诉我这里我做错了什么。感谢您的帮助。

Answer 1

您不应在sender()的回调中使用Future。在处理回调时，sender()可能指的是与收到消息时不同的内容。

首先考虑在回调之外保存引用，如：

override def receive: Actor.Receive = {
  case Message(lst) =>
        val future: Future[List[String]] = // Do Something asynchronous
        val replyTo: ActorRef = sender()
        future onComplete {
            case Success(r) => replyTo.!(r)(context.parent) // This message is not delivered to Controller actor.
            case Failure(th) => // Error handling
        }
}

甚至更好，使用管道模式：

import akka.pattern.pipe
override def receive: Actor.Receive = {
  case Message(lst) =>
    val future: Future[List[String]] = // Do Something asynchronous
    future.pipeTo(sender())
}

Akka循环：从远程路由向发送方发送响应

1 个答案: