了解崩溃时akka actor的默认行为

Question

class PingActor extends Actor with ActorLogging {
  import PingActor._
  override def postRestart(reason: Throwable): Unit = {
    log.info(s"RESTARTING")
    super.postRestart(reason)
  }
  var counter = 0
  val pongActor = context.actorOf(PongActor.props, "pongActor")
  def receive = {
    case Initialize => 
      pongActor ! PingMessage("ping")   
    case PongActor.PongMessage(text) =>
      log.info("In PingActor - received message: {}", text)
      counter += 1
      if (counter == 3) {
         log.info("FIN")
        context.system.shutdown()
      }
      if (counter == 2) {
        sender() ! PingMessage("ping")
        throw new IllegalArgumentException("Aooch")

      }
      else sender() ! PingMessage("ping")
  } 
}
object PingActor {
  val props = Props[PingActor]
  case object Initialize
  case class PingMessage(text: String)
}

class PongActor extends Actor with ActorLogging {
  import PongActor._
  def receive = {
    case PingActor.PingMessage(text) => 
      log.info("In PongActor - received message: {}", text)
      sender() ! PongMessage("pong")
  }
}

object PongActor {
  val props = Props[PongActor]
  case class PongMessage(text: String)
}

为什么在崩溃前发送消息的发件人不可用？有办法克服吗？

Answer 1

正如文档所述，重新启动参与者时的默认行为是停止该参与者的所有子角色。这就是重新启动后发送给发件人的邮件变成死信的原因。您需要重写默认行为，并在prestart()挂钩中设置子级的初始化（即pongactor)。另外，删除对super.postrestart(reason)的调用。

class PingActor extends Actor with ActorLogging {
  import PingActor._

  override def preStart(): Unit = {
    pongActor = Option(context.actorOf(PongActor.props, "pongActor"))
  }

  override def preRestart(reason: Throwable, message: Option[Any]): Unit = {
    log.info("Don't stop the children")
    postStop()
  }

  override def postRestart(reason: Throwable): Unit = {
    log.info("RESTARTING")
  }

  var counter = 0
  var pongActor: Option[ActorRef] = None

  def receive = {
    case Initialize => 
      pongActor.foreach(_ ! PingMessage("ping"))
    case PongActor.PongMessage(text) =>
      ...
  } 
}

进行上述更改会导致以下输出：

In PongActor - received message: ping
In PingActor - received message: pong
In PongActor - received message: ping
In PingActor - received message: pong
In PongActor - received message: ping
Don't stop the children
RESTARTING
In PingActor - received message: pong
In PongActor - received message: ping
In PingActor - received message: pong
In PongActor - received message: ping
Don't stop the children
RESTARTING
In PingActor - received message: pong
In PongActor - received message: ping
In PingActor - received message: pong
In PongActor - received message: ping
Don't stop the children
RESTARTING
In PingActor - received message: pong
In PongActor - received message: ping
...

除了第一个链接之外，更多关于重新启动的信息可以在这里找到。