Scheduler (Scala)

import akka.actor.Actor
import akka.actor.Props
import scala.concurrent.duration._

    //Use the system's dispatcher as ExecutionContext
    import system.dispatcher

    //Schedules to send the "foo"-message to the testActor after 50ms
    system.scheduler.scheduleOnce(50 milliseconds, testActor, "foo")

//Schedules a function to be executed (send the current time) to the testActor after 50ms
system.scheduler.scheduleOnce(50 milliseconds) {
  testActor ! System.currentTimeMillis
}

val Tick = "tick"
val tickActor = system.actorOf(Props(new Actor {
  def receive = {
    case Tick ⇒ //Do something
  }
}))
//Use system's dispatcher as ExecutionContext
import system.dispatcher

//This will schedule to send the Tick-message
//to the tickActor after 0ms repeating every 50ms
val cancellable =
  system.scheduler.schedule(0 milliseconds,
    50 milliseconds,
    tickActor,
    Tick)

//This cancels further Ticks to be sent
cancellable.cancel()

/**
 * Light-weight scheduler for running asynchronous tasks after some deadline
 * in the future. Not terribly precise but cheap.
 */
def scheduler: Scheduler

/**
 * An Akka scheduler service. This one needs one special behavior: if
 * Closeable, it MUST execute all outstanding tasks upon .close() in order
 * to properly shutdown all dispatchers.
 *
 * Furthermore, this timer service MUST throw IllegalStateException if it
 * cannot schedule a task. Once scheduled, the task MUST be executed. If
 * executed upon close(), the task may execute before its timeout.
 */
trait Scheduler {
  /**
   * Schedules a message to be sent repeatedly with an initial delay and
   * frequency. E.g. if you would like a message to be sent immediately and
   * thereafter every 500ms you would set delay=Duration.Zero and
   * interval=Duration(500, TimeUnit.MILLISECONDS)
   *
   * Java & Scala API
   */
  def schedule(
    initialDelay: FiniteDuration,
    interval: FiniteDuration,
    receiver: ActorRef,
    message: Any)(implicit executor: ExecutionContext): Cancellable

  /**
   * Schedules a function to be run repeatedly with an initial delay and a
   * frequency. E.g. if you would like the function to be run after 2 seconds
   * and thereafter every 100ms you would set delay = Duration(2, TimeUnit.SECONDS)
   * and interval = Duration(100, TimeUnit.MILLISECONDS)
   *
   * Scala API
   */
  def schedule(
    initialDelay: FiniteDuration,
    interval: FiniteDuration)(f: ⇒ Unit)(
      implicit executor: ExecutionContext): Cancellable

  /**
   * Schedules a function to be run repeatedly with an initial delay and
   * a frequency. E.g. if you would like the function to be run after 2
   * seconds and thereafter every 100ms you would set delay = Duration(2,
   * TimeUnit.SECONDS) and interval = Duration(100, TimeUnit.MILLISECONDS)
   *
   * Java API
   */
  def schedule(
    initialDelay: FiniteDuration,
    interval: FiniteDuration,
    runnable: Runnable)(implicit executor: ExecutionContext): Cancellable

  /**
   * Schedules a Runnable to be run once with a delay, i.e. a time period that
   * has to pass before the runnable is executed.
   *
   * Java & Scala API
   */
  def scheduleOnce(
    delay: FiniteDuration,
    runnable: Runnable)(implicit executor: ExecutionContext): Cancellable

  /**
   * Schedules a message to be sent once with a delay, i.e. a time period that has
   * to pass before the message is sent.
   *
   * Java & Scala API
   */
  def scheduleOnce(
    delay: FiniteDuration,
    receiver: ActorRef,
    message: Any)(implicit executor: ExecutionContext): Cancellable

  /**
   * Schedules a function to be run once with a delay, i.e. a time period that has
   * to pass before the function is run.
   *
   * Scala API
   */
  def scheduleOnce(
    delay: FiniteDuration)(f: ⇒ Unit)(
      implicit executor: ExecutionContext): Cancellable
}

/**
 * Signifies something that can be cancelled
 * There is no strict guarantee that the implementation is thread-safe,
 * but it should be good practice to make it so.
 */
trait Cancellable {
  /**
   * Cancels this Cancellable
   *
   * Java & Scala API
   */
  def cancel(): Unit

  /**
   * Returns whether this Cancellable has been cancelled
   *
   * Java & Scala API
   */
  def isCancelled: Boolean
}