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

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

@@ -0,0 +1,57 @@
+package docs.stream.cookbook
+
+import akka.stream.scaladsl._
+import akka.stream.testkit._
+import scala.concurrent.duration._
+import akka.testkit.TestLatch
+import scala.concurrent.Await
+
+class RecipeMissedTicks extends RecipeSpec {
+
+  "Recipe for collecting missed ticks" must {
+
+    "work" in {
+      type Tick = Unit
+
+      val pub = TestPublisher.probe[Tick]()
+      val sub = TestSubscriber.manualProbe[Int]()
+      val tickStream = Source.fromPublisher(pub)
+      val sink = Sink.fromSubscriber(sub)
+
+      //#missed-ticks
+      val missedTicks: Flow[Tick, Int, Unit] =
+        Flow[Tick].conflate(seed = (_) => 0)(
+          (missedTicks, tick) => missedTicks + 1)
+      //#missed-ticks
+      val latch = TestLatch(3)
+      val realMissedTicks: Flow[Tick, Int, Unit] =
+        Flow[Tick].conflate(seed = (_) => 0)(
+          (missedTicks, tick) => { latch.countDown(); missedTicks + 1 })
+
+      tickStream.via(realMissedTicks).to(sink).run()
+
+      pub.sendNext(())
+      pub.sendNext(())
+      pub.sendNext(())
+      pub.sendNext(())
+
+      val subscription = sub.expectSubscription()
+      Await.ready(latch, 1.second)
+
+      subscription.request(1)
+      sub.expectNext(3)
+
+      subscription.request(1)
+      sub.expectNoMsg(100.millis)
+
+      pub.sendNext(())
+      sub.expectNext(0)
+
+      pub.sendComplete()
+      subscription.request(1)
+      sub.expectComplete()
+    }
+
+  }
+
+}