如何处理 Akka 子 actor 的长时间初始化？

我有一个演员，它创建一个子演员来执行一些冗长的计算。

问题是子 Actor 的初始化需要几秒钟，并且父 Actor 在子 Actor 创建和完全初始化之间发送给子 Actor 的所有消息都将被丢弃。

这是我正在使用的代码的逻辑：

class ChildActor extends Actor {
  val tagger = IntializeTagger(...) // this takes a few seconds to complete

  def receive = {
    case Tag(text) => sender ! tagger.tag(text)
    case "hello" => println("Hello")
    case _ => println("Unknown message")
  }
}

class ParentActor extends Actor {
  val child = context.ActorOf(Props[ChildActor], name = "childactor")

  // the below two messages seem to get lost
  child ! "hello"
  child ! Tag("This is my sample text")

  def receive = {
     ...
  }
}

我怎样才能解决这个问题？是否可以让父 Actor 等到子 Actor 完全初始化？我将使用具有路由功能的子 Actor 并可能在远程 Actor 系统上使用。

EDIT

根据 drexin 的建议，我将代码更改为：

class ChildActor extends Actor {
  var tagger: Tagger = _

  override def preStart() = {
    tagger = IntializeTagger(...) // this takes a few seconds to complete
  }

  def receive = {
    case Tag(text) => sender ! tagger.tag(text)
    case "hello" => println("Hello")
    case _ => println("Unknown message")
  }
}

class ParentActor extends Actor {
  var child: ActorRef = _

  override def preStart() = {
    child = context.ActorOf(Props[ChildActor], name = "childactor")

    // When I add
    // Thread.sleep(5000)
    // here messages are processed without problems

    // wihout hardcoding the 5 seconds waiting 
    // the below two messages seem to get lost
    child ! "hello"
    child ! Tag("This is my sample text")
  }

  def receive = {
     ...
  }
}

但问题仍然存在。我缺少什么？

不要初始化tagger在构造函数中，但是在preStart钩子，这样消息将被收集在消息框中，并在参与者准备好时传递。

edit:

你应该对你的演员创作做同样的事情ParentActor类，因为你也会遇到同样的问题，如果ChildActor会在之前做出回应ParentActor已初始化。

edit2:

我创建了一个简单的示例，但无法重现您的问题。下面的代码工作得很好：

import akka.actor._

case class Tag(x: String)

class ChildActor extends Actor {
  type Tagger = String => String
  var tagger: Tagger = _

  override def preStart() = {
    tagger = (x: String) => x+"@tagged" // this takes a few seconds to complete
    Thread.sleep(2000) // simulate time taken to initialize Tagger
  }

  def receive = {
    case Tag(text) => sender ! tagger(text)
    case "hello" => println("Hello")
    case _ => println("Unknown message")
  }
}

class ParentActor extends Actor {
  var child: ActorRef = _

  override def preStart() = {
    child = context.actorOf(Props[ChildActor], name = "childactor")

    // When I add
    // Thread.sleep(5000)
    // here messages are processed without problems

    // wihout hardcoding the 5 seconds waiting 
    // the below two messages seem to get lost
    child ! "hello"
    child ! Tag("This is my sample text")
  }

  def receive = {
    case x => println(x)
  }
}

object Main extends App {

  val system = ActorSystem("MySystem")

  system.actorOf(Props[ParentActor])
}

输出是：

[info] Running Main
Hello
This is my sample text@tagged