scala - 考虑到结果不能作为来自同一消息的响应，如何通过询问 Akka Actor 来获得 Promise（或 Future）

Question

我遵循了本教程：http ://doc.akka.io/docs/akka/2.0/intro/getting-started-first-scala.html

基本上有一个主actor响应这两个消息：

def receive = {
    case Calculate => {
      //....
    }
    case Result(value) => {
      //....
    }
}

我们发送消息“计算”，经过几次“结果”（来自奴隶演员）我们有正确的计算

现在我在 play2 控制器的一个动作中，我正在使用这个：

val promise = (master ? Calculate)(10.seconds).mapTo[String].asPromise

不幸的是（显然）我什么也没得到，因为Calculate消息确实回复了发件人的消息。

我想以某种方式让 Akka Actor 等待......并且当计算完成时将消息发送回发送者。

但是如何？...除非我以错误的方式建模！

Answer 1

您应该forward将消息发送给从属设备（保持相同的发件人），或者将发件人包含在发给从属设备的消息中。例如：

def receive = {
  case Calculate => slave ! CalculateWithSender(sender)

  case res @ Result(value, originalSender) =>        
    val result = resultMap(originalSender) + res   // assuming results are just added
    resultMap += (originalSender -> result) 
    if (resultsAreFinished(originalSender))    
      originalSender ! result
}

或者

def receive = {
  case Calculate => slave.forward(Calculate)

  case res @ Result(value, originalSender) => 
    val result = resultMap(originalSender) + res   // assuming results are just added 
    resultMap += (originalSender -> result) 
    if (resultsAreFinished(originalSender))    
      originalSender ! result
}

或者

def receive = {
  case Calculate => slave.tell(Calculate, sender)

  case res @ Result(value, originalSender) => 
    val result = resultMap(originalSender) + res   // assuming results are just added 
    resultMap += (originalSender -> result) 
    if (resultsAreFinished(originalSender))    
      originalSender ! result
}

我不熟悉 Play 承诺，但?( ask) 返回 Akka Future。如果.asPromise将 Akka 转换Future为 Play Promise，那么您就设置好了。

Answer 2

为每个计算启动一个新参与者。将Calculate消息转发给新的actor。新参与者存储原始发件人。当结果准备好时，结果被发送给原始发送者，并且临时 actor 死亡：

class CalculateActor extends Actor {
    var origSender : ActorRef = _
    def receive {
        case Calculate => {
            origSender = sender
            slaveActors ! doStuff
            //....
    }
    case Result(value) => {
        if(results are ready) {
            origSender ! results
            self ! PoisonPill  // I'm done, time to die
        }
    }
}

class MasterActor extends Actor {
    def receive {
        case msg @ Calculate => {
            // forward sends without changing the sender
            context.actorOf(Props(new CalculateActor)).forward(msg)
        }
    }
}