+doc #15239: Stream cookbook

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

@@ -0,0 +1,58 @@
+package docs.stream.cookbook
+
+import akka.stream.OverflowStrategy
+import akka.stream.scaladsl._
+import akka.stream.testkit.StreamTestKit.SubscriberProbe
+
+import scala.collection.immutable
+import scala.concurrent.Await
+import scala.concurrent.duration._
+
+class RecipeDroppyBroadcast extends RecipeSpec {
+
+  "Recipe for a droppy broadcast" must {
+    "work" in {
+      val myElements = Source(immutable.Iterable.tabulate(100)(_ + 1))
+
+      val sub1 = SubscriberProbe[Int]()
+      val sub2 = SubscriberProbe[Int]()
+      val mySink1 = Sink(sub1)
+      val mySink2 = Sink(sub2)
+      val futureSink = Sink.head[Seq[Int]]
+      val mySink3 = Flow[Int].grouped(200).to(futureSink)
+
+      //#droppy-bcast
+      // Makes a sink drop elements if too slow
+      def droppySink[T](sink: Sink[T], bufferSize: Int): Sink[T] = {
+        Flow[T].buffer(bufferSize, OverflowStrategy.dropHead).to(sink)
+      }
+
+      import FlowGraphImplicits._
+      val graph = FlowGraph { implicit builder =>
+        val bcast = Broadcast[Int]("broadcast")
+
+        myElements ~> bcast
+
+        bcast ~> droppySink(mySink1, 10)
+        bcast ~> droppySink(mySink2, 10)
+        bcast ~> droppySink(mySink3, 10)
+      }
+      //#droppy-bcast
+
+      Await.result(graph.run().get(futureSink), 3.seconds).sum should be(5050)
+
+      sub1.expectSubscription().request(10)
+      sub2.expectSubscription().request(10)
+
+      for (i <- 91 to 100) {
+        sub1.expectNext(i)
+        sub2.expectNext(i)
+      }
+
+      sub1.expectComplete()
+      sub2.expectComplete()
+
+    }
+  }
+
+}