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| package akka_streams_test | |
| import akka.actor.ActorSystem | |
| import akka.stream._ | |
| import akka.stream.scaladsl.{Flow, Keep, Sink, Source} | |
| import scala.concurrent.Future | |
| object ConsistentHashingParallelism extends App { | |
| implicit val system = ActorSystem("ConsistentHashingParallelism") | |
| implicit val materializer = ActorMaterializer() | |
| import system.dispatcher | |
| case class Elem(id: Int, n: Int) | |
| val parallelism = 10 | |
| val source = Source.queue[Elem](Int.MaxValue, OverflowStrategy.fail) | |
| val sink = Sink.seq[Elem] | |
| val flow = Flow[Elem] | |
| .groupBy(parallelism, x => math.abs(x.id.hashCode() % parallelism)) | |
| .map { x => Thread.sleep(1); x } | |
| .mergeSubstreams | |
| val (queue, seq) = source.via(flow).toMat(sink)(Keep.both).run() | |
| val futures = for { | |
| id <- 1 to 10 | |
| } yield Future { | |
| Thread.sleep(1) | |
| for { | |
| n <- 1 to 1000 | |
| } queue.offer(Elem(id, n)) | |
| } | |
| Future.sequence(futures) onSuccess { case _ => queue.complete() } | |
| for { | |
| seq <- seq | |
| } { | |
| for { | |
| (id, elems) <- seq.groupBy(_.id) | |
| } { | |
| val ns = elems map { _.n } | |
| println(s"$id: ${ ns.sorted == ns }") | |
| } | |
| system.terminate() | |
| } | |
| } |
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To parallelize computation and make sure we preserve order of elements with same
id