+str 18735: Added keepalive inject and initial delay ops

Also, improved documentation of timeout operations
Added missing Java DSL smoke tests

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

@@ -10,68 +10,16 @@ class RecipeKeepAlive extends RecipeSpec {
   "Recipe for injecting keepalive messages" must {
 
     "work" in {
-
-      type Tick = Unit
-
-      val tickPub = TestPublisher.probe[Tick]()
-      val dataPub = TestPublisher.probe[ByteString]()
-      val sub = TestSubscriber.manualProbe[ByteString]()
-      val ticks = Source(tickPub)
-
-      val dataStream = Source(dataPub)
       val keepaliveMessage = ByteString(11)
-      val sink = Sink(sub)
 
       //#inject-keepalive
-      val tickToKeepAlivePacket: Flow[Tick, ByteString, Unit] = Flow[Tick]
-        .conflate(seed = (tick) => keepaliveMessage)((msg, newTick) => msg)
-
-      val graph = RunnableGraph.fromGraph(FlowGraph.create() { implicit builder =>
-        import FlowGraph.Implicits._
-        val unfairMerge = builder.add(MergePreferred[ByteString](1))
-
-        // If data is available then no keepalive is injected
-        dataStream ~> unfairMerge.preferred
-        ticks ~> tickToKeepAlivePacket ~> unfairMerge ~> sink
-        ClosedShape
-      })
+      import scala.concurrent.duration._
+      val injectKeepAlive: Flow[ByteString, ByteString, Unit] =
+        Flow[ByteString].keepAlive(1.second, () => keepaliveMessage)
       //#inject-keepalive
 
-      graph.run()
-
-      val subscription = sub.expectSubscription()
-
-      // FIXME RK: remove (because I think this cannot deterministically be tested and it might also not do what it should anymore)
-
-      tickPub.sendNext(())
-
-      // pending data will overcome the keepalive
-      dataPub.sendNext(ByteString(1))
-      dataPub.sendNext(ByteString(2))
-      dataPub.sendNext(ByteString(3))
-
-      subscription.request(1)
-      sub.expectNext(ByteString(1))
-      subscription.request(2)
-      sub.expectNext(ByteString(2))
-      // This still gets through because there is some intrinsic fairness caused by the FIFO queue in the interpreter
-      // Expecting here a preferred element also only worked true accident with the old Pump.
-      sub.expectNext(keepaliveMessage)
-
-      subscription.request(1)
-      sub.expectNext(ByteString(3))
-
-      subscription.request(1)
-      tickPub.sendNext(())
-      sub.expectNext(keepaliveMessage)
-
-      dataPub.sendComplete()
-      tickPub.sendComplete()
-
-      sub.expectComplete()
-
+      // No need to test, this is a built-in stage with proper tests
     }
-
   }
 
 }

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

@@ -368,8 +368,6 @@ Injecting keep-alive messages into a stream of ByteStrings
 **Situation:** Given a communication channel expressed as a stream of ByteStrings we want to inject keep-alive messages
 but only if this does not interfere with normal traffic.
 
-All this recipe needs is the ``MergePreferred`` element which is a version of a merge that is not fair. In other words,
-whenever the merge can choose because multiple upstream producers have elements to produce it will always choose the
-preferred upstream effectively giving it an absolute priority.
+There is a built-in operation that allows to do this directly:
 
 .. includecode:: code/docs/stream/cookbook/RecipeKeepAlive.scala#inject-keepalive