CODEWITHSUNDEEP
javaplayframework-2.0akka
tinazheng
tinazheng

Reputation: 163

Scheduling a block of code to run every few seconds inside Akka actor in Play 2.4.2

I have an actor class, Manager extends UntypedActor that contains a list of messages: listOfMessages, a list of client WebSocket connections: clientConnections, and a method sendMessagesToClient that sends every message in listOfMessages to every client, and then resets listOfMessages to an empty list. I want the method sendMessagesToClient executed every 2 seconds.

Is there a way to schedule a method to run on an interval from within an actor? Most docs only show how to schedule a task for a different actor, as shown here:

system.scheduler().schedule(
    Duration.create(0, TimeUnit.MILLISECONDS), //Initial delay 0 milliseconds
    Duration.create(30, TimeUnit.MINUTES),     //Frequency 30 minutes
    testActor,
    "tick",
    system.dispatcher(),
    null
);

but I want something like this inside the Manager class:

system.scheduler().schedule(
    Duration.create(0, MILLISECONDS),
    Durant.create(2, "seconds"),
    sendMessagesToClient()
);

Is this possible?

Upvotes: 0

Views: 985

Answers (1)

mattinbits
mattinbits

Reputation: 10428

Yes this is certainly possible. The method I prefer is to have the actor send a message to itself, and within the Receive, call the method which you want to have executed. For example (in Scala since that it how I use Akka):

class Example extends Actor {

  override def preStart() {
    system.scheduler().schedule(
     Duration.create(0, TimeUnit.MILLISECONDS), //Initial delay 0 milliseconds
     Duration.create(30, TimeUnit.MINUTES),     //Frequency 30 minutes
     self, //Send the message to itself
     "tick",
     system.dispatcher(),
     null
   );
  }

  def receive = {
   case "tick" => sendMessagesToClient()
  }

  def sendMessagesToClient() {
    //do work
  }
}

This actor will, as soon as it starts, schedule the regular sending of the message "tick" to itself.

One of the advantages I see in handling the scheduling this way is that it queues the work done by "tick" along with any other work to be done by the Actor, so it helps to ensure that the Actor continues to perform only one task at once, keeping the thread safety within the actor.

Upvotes: 1

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