Scala example source code file (TerminationMonitor.scala)

This example Scala source code file (TerminationMonitor.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

actor, boolean, collection, ischeduler, none, some, terminationmonitor, trackedreactor, unit

The TerminationMonitor.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2005-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala.actors
package scheduler

import scala.collection.mutable

private[scheduler] trait TerminationMonitor {
  _: IScheduler =>

  protected var activeActors = 0
  protected val terminationHandlers = new mutable.HashMap[TrackedReactor, () => Unit]
  private var started = false

  /** newActor is invoked whenever a new actor is started. */
  def newActor(a: TrackedReactor) = synchronized {
    activeActors += 1
    if (!started)
      started = true
  }

  /** Registers a closure to be executed when the specified
   *  actor terminates.
   *
   *  @param  a  the actor
   *  @param  f  the closure to be registered
   */
  def onTerminate(a: TrackedReactor)(f: => Unit): Unit = synchronized {
    terminationHandlers += (a -> (() => f))
  }

  /** Registers that the specified actor has terminated.
   *
   *  @param  a  the actor that has terminated
   */
  def terminated(a: TrackedReactor) = {
    // obtain termination handler (if any)
    val todo = synchronized {
      terminationHandlers.get(a) match {
        case Some(handler) =>
          terminationHandlers -= a
          handler
        case None =>
          () => { /* do nothing */ }
      }
    }

    // invoke termination handler (if any)
    todo()

    synchronized {
      activeActors -= 1
    }
  }

  /** Checks whether all actors have terminated. */
  private[actors] def allActorsTerminated: Boolean = synchronized {
    started && activeActors <= 0
  }

  /** Checks for actors that have become garbage. */
  protected def gc() {}
}