A simple example of two akka streams defined with the same source returning two different Futures.

TwoAkkaStreams.scala

package com.dvidr

import scala.concurrent.ExecutionContext.Implicits.global
import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import akka.stream.scaladsl.{RunnableGraph, Sink, Source, Keep}
import scala.concurrent.Future
import scala.util.{Success, Failure}


class TwoAkkaStreams

object TwoAkkaStreams {
  def main(args: Array[String]) {
    implicit val actorSystem = ActorSystem("TwoSimpleStreams")
    implicit val materializer = ActorMaterializer()

    val sink = Sink.fold[Int, Int](0)(_ + _)
    val runnable: RunnableGraph[Future[Int]] =
      Source(1 to 10).toMat(sink)(Keep.right)

    val sum1: Future[Int] = runnable.run()
    val sum2: Future[Int] = runnable.run()

    sum1.onComplete{
      case Success(n) => println(n)
      case Failure(n) => println("Akka Actor 1 failure.")
    }

    sum2.onComplete{
      case Success(n) => println(n)
      case Failure(n) => println("Akka Actor 2 failure.")
    }
  }

}