Timing futures in Scala

timedfuture.scala

import scala.concurrent.Future

object TimingFutures extends App{

  import scala.concurrent.ExecutionContext.Implicits.global
  

  def timedFuture[T](future: Future[T]) = {
    val start = System.currentTimeMillis()
    future.onComplete({
      case _ => println(s"Future took ${System.currentTimeMillis() - start} ms")
    })
    future
  }
  
  // I want to be able to measure how long this function would take
  def wantToMeasure = Future{
    Thread.sleep(500)
    "Foo"
  }
  
  //I dont want this function to be added to my measurement
  def extraOperation(x: String) ={
    Thread.sleep(500)
    "Bar"
  }
  
  // expect ~500 to be printed - even though ive "added" another slow operation to the future
  val result1 = timedFuture(wantToMeasure)
  result1 map extraOperation

  // expect ~1000 to be printed because i am timing a future with 2 long operations
  val result2 = timedFuture(wantToMeasure.map(extraOperation))
  
  
  readLine()
  
}