Handy for creating post http://blog.jessitron.com/2014/01/choosing-executorservice.html

ExecutorService play

import java.util.concurrent._

def now:Long = (new java.util.Date).getTime

import scala.concurrent.duration._
class Timer {
  val then = now
  def stop: Duration = (now - then).millis
  override def toString = (s"Timer started $stop ago")
}

def sleep(d: Duration) { Thread.sleep(d.toMillis)}
def tc = Thread.currentThread.getName

def sayHiInTwoSec:Runnable = {
    val t = new Timer
    val snooze:Duration = 2.seconds
    new Runnable {
      def run {
        sleep(snooze)
        println(s"Hi from $tc after sleeping $snooze, delay of ${t.stop - snooze}")
      }
    }
  }

def submitN(pool: ExecutorService, n: Int) {
  for (_ <- 1 to n) {
    pool.execute(sayHiInTwoSec)
  }
}

def poolStats(es: ExecutorService) = es match {
  case tpe: ThreadPoolExecutor =>
    println(s"Core Pool Size: ${tpe.getCorePoolSize}")
    println(s"Max  Pool Size: ${tpe.getMaximumPoolSize}")
    println(s"Queue Capacity: ${tpe.getQueue.remainingCapacity + tpe.getQueue.size}")
    println(s"Running Threads: ${tpe.getPoolSize}")
    println(s"Active  Threads: ${tpe.getActiveCount}")
    println(s"Waiting Tasks  : ${tpe.getQueue.size}")
  case _ => "Sorry, I can't dig around in a " + es.getClass.getName
}

poolStats(Executors.newCachedThreadPool)
//Core Pool Size: 0
//Max  Pool Size: 2147483647
//Queue Capacity: 0
//Running Threads: 0
//Active  Threads: 0
//Waiting Tasks  : 0
poolStats(Executors.newFixedThreadPool(2))
//Core Pool Size: 2
//Max  Pool Size: 2
//Queue Capacity: 2147483647
//Running Threads: 0
//Active  Threads: 0
//Waiting Tasks  : 0

val coreOfThree = new ThreadPoolExecutor(3,6,10, TimeUnit.SECONDS, new ArrayBlockingQueue(4))
 coreOfThree.execute(sayHiInTwoSec); poolStats(coreOfThree)

 val shortQ = new ThreadPoolExecutor(1, 2, 10, TimeUnit.SECONDS, new ArrayBlockingQueue[Runnable](2))
submitN(shortQ, 5); poolStats(shortQ) // RejectedExecutionException