How to perform asynchronous streaming computations

How to perform asynchronous streaming computations

In certain situations you need an asynchronous operation with back pressure handled. For those it's as easy as adding mapAsync or mapAsyncUnordered depending on whether ordering for the elements is required or not. You will need to first provide a parallelism parameter to specify the maximum number of simultaneous operations. Then you pass the operation logic in via a function which returns a Future.

  implicit val system = ActorSystem()
  implicit val materializer = ActorMaterializer()
  implicit val ec = system.dispatcher

  def writeToKafka(batch: Seq[Int]): Future[Unit] = Future {
    println(s"Writing ${batch.size} elements to Kafka via thread '${Thread.currentThread().getName}'")
  }

  val mapAsyncStage = Source(1 to 1000000)
    .grouped(100)
    .mapAsync(10)(writeToKafka)
    .runWith(Sink.ignore)
    .onComplete(_ => system.terminate())

For mapAsync - See more in the Java or Scala documentation.

For mapAsyncUnordered - See more in the Java or Scala documentation.


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