CancelReceiveTimeout.scala

/** This does not replicate getting ReceiveTimeout after cancelling - how to replicate?
 *
 * It seems like the only way it would happen is if setReceiveTimeout(Undefined) was called outside 
 * of the actor's receive block.  Otherwise with this at the end of ActorCell invoke():
 *
 *   } finally {
 *     checkReceiveTimeout // Reschedule receive timeout
 *   }
 *
 * checkReceiveTimeout would always know to *not* schedule a new ReceiveTimeout
 * 
 * On the other hand, the below does reproduce the caveat from the setReceiveTimeout scaladoc:
 * 
 *   Please note that the receive timeout might fire and enqueue the ReceiveTimeout message right after another 
 *   message was enqueued; hence it is not guaranteed that upon reception of the receive timeout there must have 
 *   been an idle period beforehand as configured via this method. 
 */

package experiments

import akka.actor.{ReceiveTimeout, Props, Actor, ActorSystem}
import concurrent.duration._

object CancelReceiveTimeout extends App {
  val system = ActorSystem()
  implicit val ec: ExecutionContext = system.dispatcher
  var lastMessage: Option[String] = None

  val a = system.actorOf(Props(new Actor {
    def receive = {
      case ReceiveTimeout =>
        lastMessage.foreach(msg => println("ReceiveTimeout, lastMsg=" + msg))
        lastMessage = None
      case "start" =>
        context.setReceiveTimeout(1.millis)
        lastMessage = Some("start")
        println("Set receiveTimeout")
        println("Actor sleeping for 5ms")
        Thread.sleep(5)
      case "cancel" =>
        context.setReceiveTimeout(Duration.Undefined)
        lastMessage = Some("cancel")
        println("Cancelled receiveTimeout")
      case x =>
        println(s"x: $x")
    }
  }))

  println("main sleeping for 1 sec")
  Thread.sleep(1000)

  println("main sending cancel")
  a ! "cancel"

  println("main sending foo")
  a ! "foo"

  println("main sending start")
  a ! "start"

  println("main sending foo")
  a ! "foo"

  println("main sleeping for 1 sec")
  Thread.sleep(1000)

  system.shutdown()
}

/* Output:
 
main sleeping for 1 sec
main sending cancel
main sending foo
main sending start
main sending foo
main sleeping for 1 sec
Cancelled receiveTimeout
x: foo
Set receiveTimeout
Actor sleeping for 5ms
x: foo
ReceiveTimeout, lastMsg=start

 */