mapasyncunordered doesnt cap parallelism

akka-mapasync-test.scala

package sknil.flow.extract

import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import akka.stream.ActorMaterializerSettings
import akka.stream.scaladsl.Source
import scala.concurrent.Future
import java.util.concurrent.atomic.AtomicInteger
import akka.stream.scaladsl.Sink
import akka.stream.scaladsl.Flow

object MapAsyncTest {
  val system = ActorSystem()  
  val threadCount = new AtomicInteger(0)
  val threadCount2 = new AtomicInteger(0)
  import system.dispatcher
  private implicit val materializer = ActorMaterializer.create(ActorMaterializerSettings.create(system).withInputBuffer(1, 1),system)
  val src = Source.repeat("x")
  val flow = src.mapAsyncUnordered(5)(el => {
    Future {
      val cur = threadCount.incrementAndGet()
      println("Thread Count:"+cur)
      Thread.sleep(3000)
      el
    }
  })
  val flow2 = Flow[String].mapAsyncUnordered(10)(x => Future {
      val cur = threadCount2.incrementAndGet()
      println("Thread Count2:"+cur)
      Thread.sleep(3000)
      x
  })
  val sink = Sink.foreach[String] { x => threadCount.decrementAndGet();threadCount2.decrementAndGet(); }
  val graph = flow.via(flow2).to(sink)
  def main(args:Array[String]) {
    graph.run()
  }
}