Question

我有一个场景，我必须从父actor中重新启动一个子Actor。重启应遵循以下规则：

只有在完成停止后才会启动
停止和开始都应该异步发生

我现在有以下情况：

在我的父Actor中，我有一个Monix Observable，它推送事件如下：

class ParentActor extends Actor {
  ...

    override def preStart(): Unit = {
    super.preStart()

    // Observable to stream events regarding PowerPlant's
    val powerPlantEventObservable =
    // For every config.database.refreshInterval in seconds
      Observable.interval(config.database.refreshInterval)
        // We ask the actor for the latest messages
        .map(_ => (dbServiceActor ? DBServiceActor.PowerPlantEvents).mapTo[PowerPlantEventsSeq])
        .concatMap(Observable.fromFuture(_))
        .concatMap(Observable.fromIterable(_))

    // Subscriber that pipes the messages to this Actor
    cancelable := powerPlantEventObservable.subscribe { update =>
      (self ? update).map(_ => Continue)
    }
  }
}

所以上面发生的是，我要求另一个名为DBServiceActor的Actor获取事件列表，当这些事件可用时，我将它传递给ParentActor（自我更新）。 ParentActor的receive方法如下所示，这是我想重新启动子actor的地方。异步：

    override def receive: Receive = {

        case PowerPlantUpdateEvent(id, powerPlantCfg) =>
          log.info(s"Re-starting PowerPlant actor with id = $id and type ${powerPlantCfg.powerPlantType}")

          // I want to stop the actor first by finding it from the actor system
          // If it exists, do a context.stop on the Actor instance
          // Once it is stopped, I want to start it again by creating a new instance of this Actor
          // Once this new Actor instance is created, I want to signal my Monix Observer to send me the next event
      }

有什么建议吗？

编辑：所以这是根据以下帖子的建议的新接收方法：

def receive: Receive = {

    // TODO: When I restart, I need the powerPlantCfg!!! How to get it?
    case Terminated(actorRef) =>
      context.unwatch(actorRef)

    case PowerPlantCreateEvent(id, powerPlantCfg) =>
      log.info(s"Starting PowerPlant actor with id = $id and type ${powerPlantCfg.powerPlantType}")

      // Start the PowerPlant, and pipe the message to self
      startPowerPlant(id, powerPlantCfg).pipeTo(self)

    case PowerPlantUpdateEvent(id, powerPlantCfg) =>
      log.info(s"Re-starting PowerPlant actor with id = $id and type ${powerPlantCfg.powerPlantType}")

      context.child(s"$simulatorActorNamePrefix$id") match {
        case Some(actorRef) =>
          context.watch(actorRef)
          actorRef ! PoisonPill


        case None =>
          log.warning(s"No running actor instance found for id $id :: Creating a new instance")
          self ! PowerPlantCreateEvent(id, powerPlantCfg)
      }

    case PowerPlantDeleteEvent(id, powerPlantCfg) => // TODO
      log.info(s"Stopping PowerPlant actor with id = $id and type ${powerPlantCfg.powerPlantType}")

      context.child(s"$simulatorActorNamePrefix$id") match {
        case Some(actorRef) =>
          context.watch(actorRef)
          actorRef ! PoisonPill

        case None =>
          log.warning(s"No running actor instance found for id $id")
      }
  }

Answer 1

我建议如下：

// I want to stop the actor first by finding it from the actor system

要查找孩子，请使用val child = context.child(name)或浏览context.children

// If it exists, do a context.stop on the Actor instance

上面找到的孩子，你必须设置死亡监视（对下一步有用）并杀死它：

context.watch(child) // you could also consider using context.watchWith()
child ! PoisonPill

// Once it is stopped, I want to start it again by creating a new instance of this Actor

由于上面的deatch-watch设置，您的ParentActor将被通知孩子停止，只需添加一个消息处理程序：

override def receive: Receive = {
  case Terminated(child) => // you might want to check which specific child was terminated if you care
    context.unwatch(child)
    context.actorOf(...) // recreate the child actor

// Once this new Actor instance is created, I want to signal my Monix Observer to send me the next event

你可以在调用context.actorOf之后立即发出信号，如果你想确定儿童演员设法启动（即，因为某些东西可能在初始化/开始时失败），你应该拥有你的{ {1}}期待来自新创建的孩子的信号。如果启动更复杂，您可以在ParentActor或其中一个消息处理程序中将该信号从子节点发送到父节点。

Answer 2

基于Frederic A的回答，我在这里发布我的解决方案，展示了如何处理一个Actor的重启：

def waitForRestart(source: ActorRef, newMessage: Option[PowerPlantCreateEvent[PowerPlantConfig]]): Receive = {
    case Terminated(actor) =>
      context.unwatch(actor)

      newMessage match {
        case Some(powerPlantCreateEvent) =>
          self ! powerPlantCreateEvent
        case _ =>
          // just ignore
      }
      // Now unstash all of the messages
      unstashAll()

    case someDamnThing =>
      log.error(s"Unexpected message $someDamnThing :: " +
        s"received while waiting for an actor to be stopped")
      stash()
  }

这是接收方法：

def receive: Receive = {

        case Terminated(actorRef) =>
          context.unwatch(actorRef)

        case PowerPlantCreateEvent(id, powerPlantCfg) =>
          log.info(s"Starting PowerPlant actor with id = $id and type ${powerPlantCfg.powerPlantType}")

          // Start the PowerPlant, and pipe the message to self
          startPowerPlant(id, powerPlantCfg).pipeTo(self)

        case PowerPlantUpdateEvent(id, powerPlantCfg) =>
          log.info(s"Re-starting PowerPlant actor with id = $id and type ${powerPlantCfg.powerPlantType}")

          context.child(s"$simulatorActorNamePrefix$id") match {
            case Some(actorRef) =>
              context.watch(actorRef)
              // We first kill
              actorRef ! PoisonPill

              // We wait asynchronously until this Actor is re-started
              context.become(
                waitForRestart(
                  actorRef,
                  Some(PowerPlantCreateEvent(id, powerPlantCfg))
                )
              )

            case None =>
              log.warning(s"No running actor instance found for id $id :: Creating a new instance")
              self ! PowerPlantCreateEvent(id, powerPlantCfg)
          }

        case PowerPlantDeleteEvent(id, powerPlantCfg) =>
          log.info(s"Stopping PowerPlant actor with id = $id and type ${powerPlantCfg.powerPlantType}")

          context.child(s"$simulatorActorNamePrefix$id") match {
            case Some(actorRef) =>
              context.watch(actorRef)
              actorRef ! Kill

            case None =>
              log.warning(s"No running actor instance found for id $id")
          }
      }

重新启动Akka Actor和Reactive Streams Integration

2 个答案: