PhaserDemo.scala

/**
 * simple demo of using Phasers to sync completion and waiting for things to complete.
 */
import java.util.concurrent._
import java.lang.{Thread, Runnable}

/**
 * Run a function in another thread, yeah it's ugly, whatever, this is a demo.
 * This is not the interesting part.
 */
def runBackground(f: ()=>Unit) = {
        new Thread(
          new Runnable {
            override def run: Unit = {
              f.apply()
            }
          }
        ).start
      }

/**
 * wait for someone to arrive with this Phaser
 */
def patient(phaser:Phaser, millis:Long) {
  println("patient waiting")
  try {
    phaser.awaitAdvanceInterruptibly(0, millis, TimeUnit.MILLISECONDS)
    println("patient done waiting")
  } catch {
    case te: TimeoutException => {
      println("too slow! i gave up");
    }
  }
}

/** 
 * do something slow then arrive at the given Phaser
 */
def slowWriter(phaser:Phaser, slowness:Long): Unit = {
  phaser.register()
  try {
    println("slow writer snoozing")
    Thread.sleep(slowness) // do some slow thing, yeah we know this is ugly.
    println("slow writer arriving")
  } finally {
    phaser.arrive()
    println("slow writer done")
  }
}

def demo(slowness:Long, patience:Long) {
  val phaser = new Phaser
  runBackground(() => slowWriter(phaser, slowness))
  patient(phaser, patience)

}

demo(1000, 5000)