Inspiration for Akka mailing list question

MessageDiscarder.scala

import akka.actor._

object MessageDiscarder {
  case object WorkerAvailable
}

class MessageDiscarder extends Actor {
  import MessageDiscarder._

  var queued: Option[(Any, ActorRef)] = None

  def receive = {
    case WorkerAvailable => 
      queued match { 
        case Some((msg, snd)) => 
          sender.tell(msg, snd)
          queued = None
        case None =>
          context.become(idle(sender), discardOld = false)
      }
    case msg => 
      queued = Some((msg, sender))
  }

  def idle(worker: ActorRef): Actor.Receive = {
    case msg =>
      worker.tell(msg, sender)
      context.unbecome()
  }

}

class SampleWorker(discarder: ActorRef) extends Actor {
  import MessageDiscarder._

  discarder ! WorkerAvailable

  def receive = {
    case msg =>
      println("work: " + msg)
      // note that this is the original sender
      sender ! "done"
      discarder ! WorkerAvailable
  }

}