如何自行重启 Akka 演员？

Question

当子 Actor 收到自定义 RESTART 消息时，该 Actor 应自行重启。
（目的是重置actor成员变量，从db重新加载外部状态，但不清除actor内部消息队列）

要实现重新启动，一种解决方法是子 Actor 引发自定义异常，而父 Actor 配置其 OneForOneStrategy 以针对此特定异常类型重新启动子 Actor。

我想知道，是否有更直接的方法来重新启动？

Answer 1

目的是重置actor成员变量，reload external state from db

我猜，这可能是最大的问题，因为加载外部状态可能需要时间并且还会阻塞操作，因此操作的结果是或应该是Future[] - 所以在未来加载你的演员时应该忽略所有其他消息, 直到收到来自 DB 的状态。

我认为ActorCell#become 方法在这种情况下可能会对您有所帮助 - 因此您可以将接收方法更改为另一个，这将忽略其余消息，除了带有 DB 状态或数据的消息，然后切换回常规接收。

请看下面的代码示例：

  import akka.actor.Actor
  import akka.pattern._
  import scala.concurrent.Future
  import scala.collection.mutable


  // Database API and external state model example
  case class DbExternalState()
  trait Database {
    def loadExternalState: Future[DbExternalState]
  }

  import RestartActor._
  class RestartActor(database: Database) extends Actor {
    private var state = ActorState()
    private val suspendedMessages = mutable.Queue[Any]()

    override def receive: Receive = defaultReceive

    private def defaultReceive: Receive = {
      case Restart => restartActorStart()
    }

    /**
     * Wait until message with internal state received and ignore all the other messages (put back un queue)
     */
    private def suspendedReceive: Receive = {
      case ExternalStateLoaded(state) => restartActorFinish(state)
      case message => suspendedMessages.enqueue(message)
    }

    private def restartActorStart(): Unit = {
      import context.dispatcher
      context.become(suspendedReceive)
      database.loadExternalState.map(ExternalStateLoaded) pipeTo self
    }

    private def restartActorFinish(dbExternalState: DbExternalState): Unit = {
      state = ActorState.initial(dbExternalState)
      context.become(defaultReceive) // Return to normal message handling flow
      suspendedMessages.foreach(message => self ! message)
      suspendedMessages.clear()
    }
  }

  object RestartActor {
    // Restart
    case object Restart
    case class ExternalStateLoaded(state: DbExternalState)

    case class ActorState(internalState: List[String] = Nil, externalState: DbExternalState = DbExternalState())

    object ActorState {
      def initial(externalState: DbExternalState): ActorState = ActorState(externalState = externalState)
    }
  }

请告诉我建议是正确的。 我希望这会有所帮助！