+doc #19429 initial merge of docs-dev and docs

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

@@ -0,0 +1,65 @@
+package docs.stream.cookbook
+
+import akka.stream.{ ClosedShape, OverflowStrategy }
+import akka.stream.scaladsl._
+import akka.stream.testkit._
+
+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 pub = TestPublisher.probe[Int]()
+      val myElements = Source.fromPublisher(pub)
+
+      val sub1 = TestSubscriber.manualProbe[Int]()
+      val sub2 = TestSubscriber.manualProbe[Int]()
+      val sub3 = TestSubscriber.probe[Int]()
+      val futureSink = Sink.head[Seq[Int]]
+      val mySink1 = Sink.fromSubscriber(sub1)
+      val mySink2 = Sink.fromSubscriber(sub2)
+      val mySink3 = Sink.fromSubscriber(sub3)
+
+      //#droppy-bcast
+      val graph = RunnableGraph.fromGraph(GraphDSL.create(mySink1, mySink2, mySink3)((_, _, _)) { implicit b =>
+        (sink1, sink2, sink3) =>
+          import GraphDSL.Implicits._
+
+          val bcast = b.add(Broadcast[Int](3))
+          myElements ~> bcast
+
+          bcast.buffer(10, OverflowStrategy.dropHead) ~> sink1
+          bcast.buffer(10, OverflowStrategy.dropHead) ~> sink2
+          bcast.buffer(10, OverflowStrategy.dropHead) ~> sink3
+          ClosedShape
+      })
+      //#droppy-bcast
+
+      graph.run()
+
+      sub3.request(100)
+      for (i <- 1 to 100) {
+        pub.sendNext(i)
+        sub3.expectNext(i)
+      }
+
+      pub.sendComplete()
+
+      sub1.expectSubscription().request(10)
+      sub2.expectSubscription().request(10)
+
+      for (i <- 91 to 100) {
+        sub1.expectNext(i)
+        sub2.expectNext(i)
+      }
+
+      sub1.expectComplete()
+      sub2.expectComplete()
+
+    }
+  }
+
+}