如何取消Akka演员？

Question

我有一个 akka actor（worker），它接收请求并回复它。请求处理可能需要 3-60 分钟。来电者（也是演员）当前正在使用！并等待 future.get，但是如果需要，可以更改 Caller actor 的设计。另外，我目前正在使用 EventDriven 调度程序。

如何取消（用户发起的）请求处理，以便释放工作参与者并返回到就绪状态以接收新请求？我希望有一个类似于 java.util.concurrent.Future 的取消方法的方法，但在 Akka 1.1.3 中找不到

编辑：

我们尝试使用 获得我们正在寻找的行为CompleteWithException ：

object Cancel {
  def main(args: Array[String]) {
    val actor = Actor.actorOf[CancelActor].start
    EventHandler.info(this, "Getting future")
    val future = (actor ? "request").onComplete(x => EventHandler.info(this, "Completed!! " + x.get))
    Thread.sleep(500L)
    EventHandler.info(this, "Cancelling")
    future.completeWithException(new Exception("cancel"))
    EventHandler.info(this, "Future is " + future.get)
  }
}

class CancelActor extends Actor {
  def receive = {
    case "request" =>
      EventHandler.info(this, "start")
      (1 to 5).foreach(x => {
        EventHandler.info(this, "I am a long running process")
        Thread.sleep(200L)
      })
      self reply "response"
      EventHandler.info(this, "stop")
  }
}

但这并没有停止长时间运行的过程。

    [INFO]    [9/16/11 1:46 PM] [main] [Cancel$] Getting future
    [INFO]    [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] start
    [INFO]    [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process
    [INFO]    [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process
    [INFO]    [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process
    [INFO]    [9/16/11 1:46 PM] [main] [Cancel$] Cancelling
    [ERROR]   [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-7] [ActorCompletableFuture] 
    java.lang.Exception: cancel
        at kozo.experimental.Cancel$.main(Cancel.scala:15)
...

    [INFO]    [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process
    [INFO]    [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] I am a long running process
    [INFO]    [9/16/11 1:46 PM] [akka:event-driven:dispatcher:global-2] [CancelActor] stop

相反，考虑 java.util.concurrent.Future 的行为：

object Cancel2 {
  def main(args: Array[String]) {
    val executor: ExecutorService = Executors.newSingleThreadExecutor()
    EventHandler.info(this, "Getting future")
    val future = executor.submit(new Runnable {
      def run() {
        EventHandler.info(this, "start")
        (1 to 5).foreach(x => {
          EventHandler.info(this, "I am a long running process")
          Thread.sleep(200L)
        })
      }
    })
    Thread.sleep(500L)
    EventHandler.info(this, "Cancelling")
    future.cancel(true)
    EventHandler.info(this, "Future is " + future.get)
  }
}

这确实会停止长时间运行的进程

    [INFO]    [9/16/11 1:48 PM] [main] [Cancel2$] Getting future
    [INFO]    [9/16/11 1:48 PM] [pool-1-thread-1] [anon$1] start
    [INFO]    [9/16/11 1:48 PM] [pool-1-thread-1] [anon$1] I am a long running process
    [INFO]    [9/16/11 1:48 PM] [pool-1-thread-1] [anon$1] I am a long running process
    [INFO]    [9/16/11 1:48 PM] [pool-1-thread-1] [anon$1] I am a long running process
    Exception in thread "main" java.util.concurrent.CancellationException
...
    [INFO]    [9/16/11 1:48 PM] [main] [Cancel2$] Cancelling

Answer 1

您还可以检查 Actor 中 Future 的状态。

class MyActor extends Actor {
  def receive = {
    case msg =>
      while(!self.senderFuture.get.isCompleted) {
        performWork(msg)
      }
      self reply result
  }
  ...
}

这要求消息发送时带有“？”或者“问”。
希望有帮助。

Answer 2

如果您只是在虚拟机中，您可以将 AtomicBoolean 与您的 Job 消息一起传递，并间歇性地在您的 Actor 中检查它，看看是否应该中止。

actor ! Job(..., someAtomicBoolean)

class MyActor extends Actor {
  def receive = {
    case Job(..., cancelPlease) =>
      while(cancelPlease.get == false) {
        performWork
      }
      self reply result
  }
}