+doc: Added section about buffering

akka-docs-dev/rst/scala/code/docs/stream/StreamBuffersRateSpec.scala

@@ -0,0 +1,60 @@
+package docs.stream
+
+import akka.stream.{ OverflowStrategy, MaterializerSettings, FlowMaterializer }
+import akka.stream.scaladsl._
+import akka.stream.testkit.AkkaSpec
+
+class StreamBuffersRateSpec extends AkkaSpec {
+  implicit val mat = FlowMaterializer()
+
+  "Demonstrate pipelining" in {
+    //#pipelining
+    Source(1 to 3)
+      .map { i => println(s"A: $i"); i }
+      .map { i => println(s"B: $i"); i }
+      .map { i => println(s"C: $i"); i }
+      .runWith(Sink.ignore)
+    //#pipelining
+  }
+
+  "Demonstrate buffer sizes" in {
+    //#materializer-buffer
+    val materializer = FlowMaterializer(
+      MaterializerSettings(system)
+        .withInputBuffer(
+          initialSize = 64,
+          maxSize = 64))
+    //#materializer-buffer
+
+    //#section-buffer
+    val flow =
+      Flow[Int]
+        .section(OperationAttributes.inputBuffer(initial = 1, max = 1)) { sectionFlow =>
+          // the buffer size of this map is 1
+          sectionFlow.map(_ * 2)
+        }
+        .map(_ / 2) // the buffer size of this map is the default
+    //#section-buffer
+  }
+
+  "buffering abstraction leak" in {
+    //#buffering-abstraction-leak
+    import scala.concurrent.duration._
+    case class Tick()
+
+    FlowGraph { implicit b =>
+      import FlowGraphImplicits._
+
+      val zipper = ZipWith[Tick, Int, Int]((tick, count) => count)
+
+      Source(initialDelay = 1.second, interval = 1.second, () => "message!")
+        .conflate(seed = (_) => 1)((count, _) => count + 1) ~> zipper.right
+
+      Source(initialDelay = 3.second, interval = 3.second, () => Tick()) ~> zipper.left
+
+      zipper.out ~> Sink.foreach(println)
+    }
+    //#buffering-abstraction-leak
+  }
+
+}