MapConcurrentLeak.scala

import com.twitter.concurrent.AsyncStream
import com.twitter.concurrent.AsyncStream._
import com.twitter.util.{Await, Future}

object MapConcurrentLeak extends App{

  def stream(i: Int, stop: Int): AsyncStream[Int] = {
    if (i >= stop) fromFuture(Future.never)
    else i +:: stream(i + 1, stop)
  }

  Await.ready(
    stream(0, 1000000)
      .mapConcurrent(10)(_ => Future.Done)
      .force
  )

}