+doc #15239: Stream cookbook

akka-docs-dev/rst/scala/code/docs/stream/cookbook/RecipeWorkerPool.scala

@@ -0,0 +1,53 @@
+package docs.stream.cookbook
+
+import akka.stream.scaladsl._
+import akka.testkit.TestProbe
+
+import scala.concurrent.Await
+import scala.concurrent.duration._
+
+class RecipeWorkerPool extends RecipeSpec {
+
+  "Recipe for a pool of workers" must {
+
+    "work" in {
+      val myJobs = Source(List("1", "2", "3", "4", "5"))
+      type Result = String
+
+      val worker = Flow[String].map(_ + " done")
+
+      //#worker-pool
+      def balancer[In, Out](worker: Flow[In, Out], workerCount: Int): Flow[In, Out] = {
+        import FlowGraphImplicits._
+
+        Flow[In, Out]() { implicit graphBuilder =>
+          val jobsIn = UndefinedSource[In]
+          val resultsOut = UndefinedSink[Out]
+
+          val balancer = Balance[In](waitForAllDownstreams = true)
+          val merge = Merge[Out]("merge")
+
+          jobsIn ~> balancer // Jobs are fed into the balancer
+          merge ~> resultsOut // the merged results are sent out
+
+          for (_ <- 1 to workerCount) {
+            // for each worker, add an edge from the balancer to the worker, then wire
+            // it to the merge element
+            balancer ~> worker ~> merge
+          }
+
+          (jobsIn, resultsOut)
+        }
+      }
+
+      val processedJobs: Source[Result] = myJobs.via(balancer(worker, 3))
+      //#worker-pool
+
+      Await.result(processedJobs.grouped(10).runWith(Sink.head), 3.seconds).toSet should be(Set(
+        "1 done", "2 done", "3 done", "4 done", "5 done"))
+
+    }
+
+  }
+
+}