I need an actor to send a message every minute. How do I best achieve this behaviour? I am afraid of using java.lang.Thread.sleep(long millis)
as a thread can be shared among many actors in Scala, as far as I understand.
You can use Akka FSM to model an actor that stays forMax
millis in a waiting state and then sends a message, e.g. by switching to another state while using onTransition
and staying there for 0 millis to switch back to waiting state. There is a good example at the akka page.
Create an actor with receiveWithin
to act as the timer.
import scala.actors._
class Wakeup[A](millis: Int, who: ReplyReactor, alarm: A) extends Thread {
val done = new java.util.concurrent.atomic.AtomicBoolean(false)
override def run {
while (!done.get()) {
who ! alarm
Thread.sleep(millis)
}
}
}
case object BEEP {}
val a = new ReplyReactor { def act { loop { react {
case BEEP => println("Wha?! "+new java.util.Date)
case _ =>
}}}}
val b = new Wakeup(60000,a,BEEP)
a.start
Why use an actor when a thread is what you want?
scala> b.start
scala> Wha?! Mon Nov 07 18:43:18 EST 2011
Wha?! Mon Nov 07 18:44:18 EST 2011
Wha?! Mon Nov 07 18:45:18 EST 2011
Wha?! Mon Nov 07 18:46:18 EST 2011
Wha?! Mon Nov 07 18:47:18 EST 2011
Wha?! Mon Nov 07 18:48:18 EST 2011
Wha?! Mon Nov 07 18:49:18 EST 2011
Wha?! Mon Nov 07 18:50:18 EST 2011
Wha?! Mon Nov 07 18:51:18 EST 2011
Wha?! Mon Nov 07 18:52:18 EST 2011
I ended up in creation of dedicated Runnable instance, which keeps sending a message to the target actor. Like
case class QueueTick()
class QueueWatcherActor extends Actor {
override def receive = {
case QueueTick() => // do it here
}
}
val ref = ActorSystem("xxx")
val actor = ref.actorOf(Props[QueueWatcherActor])
val executor = Executors.newSingleThreadScheduledExecutor()
executor.scheduleAtFixedRate(new Runnable {
def run() {
actor ! QueueTick()
}
},1,60,TimeUnit.SECONDS)
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