scala - 按需 Actor 获取或创建

Question

我可以用 actorOf 创建 Actor 并用 actorFor 查看它们.我现在想找个 Actor id:String如果它不存在，我希望它被创建。像这样的东西:

  def getRCActor(id: String):ActorRef = {
    Logger.info("getting actor %s".format(id))
    var a = system.actorFor(id)
    if(a.isTerminated){
      Logger.info("actor is terminated, creating new one")
      return system.actorOf(Props[RC], id:String)
    }else{
      return a
    }
   }

但这不适用于 isTerminated总是正确的，我得到 actor name 1 is not unique!第二次通话异常(exception)。我想我在这里使用了错误的模式。有人可以帮助如何实现这一目标吗？我需要

按需创建 Actor

按 id 查找 Actor ，如果不存在则创建他们

破坏的能力，因为我不知道我是否会再次需要它

我应该为此使用调度程序还是路由器？

解决方案
正如提议的那样，我使用了一个具体的主管，将可用的 Actor 保存在 map 中。可以要求提供他的一个 child 。

class RCSupervisor extends Actor {

  implicit val timeout = Timeout(1 second)
  var as = Map.empty[String, ActorRef]

  def getRCActor(id: String) = as get id getOrElse {
    val c = context actorOf Props[RC]
    as += id -> c
    context watch c
    Logger.info("created actor")
    c
  }

  def receive = {

    case Find(id) => {
      sender ! getRCActor(id)
    }

    case Terminated(ref) => {
      Logger.info("actor terminated")
      as = as filterNot { case (_, v) => v == ref }
    }
  }
}

他的同伴对象

object RCSupervisor {

  // this is specific to Playframework (Play's default actor system)
  var supervisor = Akka.system.actorOf(Props[RCSupervisor])

  implicit val timeout = Timeout(1 second)

  def findA(id: String): ActorRef = {
    val f = (supervisor ? Find(id))
    Await.result(f, timeout.duration).asInstanceOf[ActorRef]
  }
  ...
}

Answer 1

我基于 oxbow_lakes 的代码/建议来解决这个问题，但我没有创建所有子角色的简单集合，而是使用(双向) map ，如果子角色的数量很大，这可能是有益的。

import play.api._
import akka.actor._
import scala.collection.mutable.Map 

trait ResponsibleActor[K] extends Actor {
  val keyActorRefMap: Map[K, ActorRef] = Map[K, ActorRef]()
  val actorRefKeyMap: Map[ActorRef, K] = Map[ActorRef, K]()

  def getOrCreateActor(key: K, props: => Props, name: => String): ActorRef = {
    keyActorRefMap get key match {
      case Some(ar) => ar
      case None =>  {
        val newRef: ActorRef = context.actorOf(props, name)
        //newRef shouldn't be present in the map already (if the key is different)
        actorRefKeyMap get newRef match{
          case Some(x) => throw new Exception{}
          case None =>
        }
        keyActorRefMap += Tuple2(key, newRef)
        actorRefKeyMap += Tuple2(newRef, key)
        newRef
      }
    }
  }

  def getOrCreateActorSimple(key: K, props: => Props): ActorRef = getOrCreateActor(key, props, key.toString)

  /**
   * method analogous to Actor's receive. Any subclasses should implement this method to handle all messages
   * except for the Terminate(ref) message passed from children
   */
  def responsibleReceive: Receive

  def receive: Receive = {
    case Terminated(ref) => {
      //removing both key and actor ref from both maps
      val pr: Option[Tuple2[K, ActorRef]] = for{
        key <- actorRefKeyMap.get(ref)
        reref <- keyActorRefMap.get(key)
      } yield (key, reref)

      pr match {
        case None => //error
        case Some((key, reref)) => {
          actorRefKeyMap -= ref
          keyActorRefMap -= key
        }
      }
    }
    case sth => responsibleReceive(sth)
  }
}

要使用从 ResponsibleActor 继承的功能并实现 responsibleReceive .注意:此代码尚未经过彻底测试，可能仍有一些问题。我省略了一些错误处理以提高可读性。