让演员睡觉

Question

我想让一个演员睡上一段时间，具体来说，它应该决定是否让自己睡，这取决于一种情况：

class MyActor extends Actor {
  def receive {
    case "doWork" => doWork()
  }

  def doWork(): Unit = {
    // doing some work
    val condition = calculateCondition
    if (condition) {
      // sleep for 5 seconds
      // Thread.sleep(5000) 
    }
  }
}

我很确定在演员里面叫Thread.sleep(5000)不是件好事，而且应该有另外一种方法。因此，我如何使它睡觉呢？

Answer 1

我希望通过改变行为者的状态/行为来实现这一点。Akka为您提供了几种这样做的方法:您可以实现一个完整的状态机，或者使用context.become (并混合在akka.actor.Stash中)，并让参与者传递(计划)消息给自己。对于这种情况，前者感觉太过分了，所以下面是我对它进行编码的方式：

import akka.actor._    
import scala.concurrent.duration._

class MySleepyActor(duration: FiniteDuration = (5 seconds)) extends Actor with Stash {

  import context._

  override def preStart() { become(running) }

  def receive = PartialFunction.empty

  def running: Actor.Receive = {
    case "doWork" =>       
      if (doWork()) {
        scheduleReactivate
        become(paused)
      }
    case "wakeUp" => // already awake
  }

  def paused: Actor.Receive = {
    case "doWork" => stash()
    case "wakeUp" => 
      unstashAll()
      become(running)
  }

  def scheduleReactivate: Unit = {
    system.scheduler.scheduleOnce(duration, self, "wakeUp")
  }

  def doWork(): Boolean = {
    // doing some work, then:
    calculateCondition
  }
}

注意:我还没有测试过这个代码！不过，应该给你一些工作上的想法。