+doc,htc #18600,18597 documents where/how to deal with failure in Http

akka-docs-dev/rst/java.rst

@@ -1,10 +1,10 @@
 .. _stream-java-api:
 
 Java Documentation
-===================
+==================
 
 .. toctree::
-   :maxdepth: 2
+   :maxdepth: 3
 
    java/stream-index
    java/http/index

akka-docs-dev/rst/java/code/docs/http/javadsl/server/HighLevelServerBindFailureExample.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package docs.http.javadsl.server;
+
+//#binding-failure-high-level-example
+import akka.actor.ActorSystem;
+import akka.dispatch.OnFailure;
+import akka.http.javadsl.model.ContentTypes;
+import akka.http.javadsl.server.*;
+import akka.http.javadsl.server.values.Parameters;
+import akka.http.scaladsl.Http;
+import scala.concurrent.Future;
+
+import java.io.IOException;
+
+@SuppressWarnings("unchecked")
+public class HighLevelServerBindFailureExample {
+    public static void main(String[] args) throws IOException {
+        // boot up server using the route as defined below
+        final ActorSystem system = ActorSystem.create();
+
+        // HttpApp.bindRoute expects a route being provided by HttpApp.createRoute
+        Future<Http.ServerBinding> bindingFuture =
+                new HighLevelServerExample().bindRoute("localhost", 8080, system);
+
+        bindingFuture.onFailure(new OnFailure() {
+            @Override
+            public void onFailure(Throwable failure) throws Throwable {
+                System.err.println("Something very bad happened! " + failure.getMessage());
+                system.shutdown();
+            }
+        });
+
+        system.shutdown();
+    }
+}
+//#binding-failure-high-level-example

akka-docs-dev/rst/java/code/docs/http/javadsl/server/HttpServerExampleDocTest.java

@@ -5,26 +5,43 @@
 package docs.http.javadsl.server;
 
 import akka.actor.ActorSystem;
+import akka.dispatch.OnFailure;
+import akka.http.impl.util.JavaMapping;
 import akka.http.impl.util.Util;
 import akka.http.javadsl.Http;
 import akka.http.javadsl.IncomingConnection;
 import akka.http.javadsl.ServerBinding;
 import akka.http.javadsl.model.*;
+import akka.http.javadsl.model.ContentTypes;
+import akka.http.javadsl.model.HttpRequest;
+import akka.http.javadsl.model.HttpResponse;
+import akka.http.javadsl.model.Uri;
+import akka.japi.JavaPartialFunction;
 import akka.japi.function.Function;
 import akka.japi.function.Procedure;
 import akka.stream.ActorMaterializer;
 import akka.stream.Materializer;
+import akka.stream.javadsl.Flow;
 import akka.stream.javadsl.Sink;
 import akka.stream.javadsl.Source;
+import akka.stream.stage.Context;
+import akka.stream.stage.PushStage;
+import akka.stream.stage.SyncDirective;
+import akka.stream.stage.TerminationDirective;
+import akka.util.ByteString;
+import scala.Function1;
 import scala.concurrent.Await;
 import scala.concurrent.Future;
 import scala.concurrent.duration.FiniteDuration;
+import scala.runtime.BoxedUnit;
 
 import java.io.BufferedReader;
 import java.io.InputStreamReader;
 import java.util.concurrent.TimeUnit;
 
+@SuppressWarnings("unused")
 public class HttpServerExampleDocTest {
+
     public static void bindingExample() throws Exception {
         //#binding-example
         ActorSystem system = ActorSystem.create();
@@ -45,6 +62,116 @@ public class HttpServerExampleDocTest {
         //#binding-example
         Await.result(serverBindingFuture, new FiniteDuration(3, TimeUnit.SECONDS));
     }
+
+    public static void bindingFailureExample() throws Exception {
+        //#binding-failure-handling
+        ActorSystem system = ActorSystem.create();
+        Materializer materializer = ActorMaterializer.create(system);
+
+        Source<IncomingConnection, Future<ServerBinding>> serverSource =
+            Http.get(system).bind("localhost", 80, materializer);
+
+        Future<ServerBinding> serverBindingFuture =
+            serverSource.to(Sink.foreach(
+                new Procedure<IncomingConnection>() {
+                    @Override
+                    public void apply(IncomingConnection connection) throws Exception {
+                        System.out.println("Accepted new connection from " + connection.remoteAddress());
+                        // ... and then actually handle the connection
+                    }
+                })).run(materializer);
+
+        serverBindingFuture.onFailure(new OnFailure() {
+            @Override
+            public void onFailure(Throwable failure) throws Throwable {
+                // possibly report the failure somewhere...
+            }
+        }, system.dispatcher());
+        //#binding-failure-handling
+        Await.result(serverBindingFuture, new FiniteDuration(3, TimeUnit.SECONDS));
+    }
+
+    public static void connectionSourceFailureExample() throws Exception {
+        //#incoming-connections-source-failure-handling
+        ActorSystem system = ActorSystem.create();
+        Materializer materializer = ActorMaterializer.create(system);
+
+        Source<IncomingConnection, Future<ServerBinding>> serverSource =
+            Http.get(system).bind("localhost", 8080, materializer);
+
+        Flow<IncomingConnection, IncomingConnection, BoxedUnit> failureDetection =
+            Flow.of(IncomingConnection.class).transform(() ->
+                new PushStage<IncomingConnection, IncomingConnection>() {
+                    @Override
+                    public SyncDirective onPush(IncomingConnection elem, Context<IncomingConnection> ctx) {
+                        return ctx.push(elem);
+                    }
+
+                    @Override
+                    public TerminationDirective onUpstreamFailure(Throwable cause, Context<IncomingConnection> ctx) {
+                        // signal the failure to external monitoring service!
+                        return super.onUpstreamFailure(cause, ctx);
+                    }
+                });
+
+        Future<ServerBinding> serverBindingFuture =
+                serverSource
+                        .via(failureDetection) // feed signals through our custom stage
+                        .to(Sink.foreach(
+                                new Procedure<IncomingConnection>() {
+                                    @Override
+                                    public void apply(IncomingConnection connection) throws Exception {
+                                        System.out.println("Accepted new connection from " + connection.remoteAddress());
+                                        // ... and then actually handle the connection
+                                    }
+                                })).run(materializer);
+        //#incoming-connections-source-failure-handling
+        Await.result(serverBindingFuture, new FiniteDuration(3, TimeUnit.SECONDS));
+    }
+
+    public static void connectionStreamFailureExample() throws Exception {
+        //#connection-stream-failure-handling
+        ActorSystem system = ActorSystem.create();
+        Materializer materializer = ActorMaterializer.create(system);
+
+        Source<IncomingConnection, Future<ServerBinding>> serverSource =
+            Http.get(system).bind("localhost", 8080, materializer);
+
+        Flow<HttpRequest, HttpRequest, BoxedUnit> failureDetection =
+                Flow.of(HttpRequest.class).transform(() ->
+                new PushStage<HttpRequest, HttpRequest>() {
+                    @Override
+                    public SyncDirective onPush(HttpRequest elem, Context<HttpRequest> ctx) {
+                        return ctx.push(elem);
+                    }
+
+                    @Override
+                    public TerminationDirective onUpstreamFailure(Throwable cause, Context<HttpRequest> ctx) {
+                        // signal the failure to external monitoring service!
+                        return super.onUpstreamFailure(cause, ctx);
+                    }
+                });
+
+        Flow<HttpRequest, HttpResponse, BoxedUnit> httpEcho =
+                Flow.of(HttpRequest.class)
+                    .via(failureDetection)
+                    .map(request -> {
+                        Source<ByteString, ?> bytes = request.entity().getDataBytes();
+                        HttpEntity entity = HttpEntities.create(ContentTypes.TEXT_PLAIN, (Source<ByteString, Object>) bytes);
+                        return HttpResponse.create()
+                                .withEntity(entity);
+                    });
+
+        Future<ServerBinding> serverBindingFuture =
+            serverSource.to(Sink.foreach(con -> {
+                        System.out.println("Accepted new connection from " + con.remoteAddress());
+                        con.handleWith(httpEcho, materializer);
+                    }
+                )).run(materializer);
+        //#connection-stream-failure-handling
+        Await.result(serverBindingFuture, new FiniteDuration(3, TimeUnit.SECONDS));
+    }
+
     public static void fullServerExample() throws Exception {
         //#full-server-example
             ActorSystem system = ActorSystem.create();

akka-docs-dev/rst/java/http/http-model.rst

@@ -42,11 +42,11 @@ HttpRequest
 
 An ``HttpRequest`` consists of
 
- - a method (GET, POST, etc.)
- - a URI
- - a seq of headers
- - an entity (body data)
- - a protocol
+- a method (GET, POST, etc.)
+- a URI
+- a seq of headers
+- an entity (body data)
+- a protocol
 
 Here are some examples how to construct an ``HttpRequest``:
 
@@ -64,10 +64,10 @@ HttpResponse
 
 An ``HttpResponse`` consists of
 
- - a status code
- - a list of headers
- - an entity (body data)
- - a protocol
+- a status code
+- a list of headers
+- an entity (body data)
+- a protocol
 
 Here are some examples how to construct an ``HttpResponse``:
 

akka-docs-dev/rst/java/http/index.rst

@@ -31,11 +31,11 @@ akka-http-jackson
 .. toctree::
    :maxdepth: 2
 
-   configuration
    http-model
    server-side/low-level-server-side-api
    server-side/websocket-support
    routing-dsl/index
    client-side/index
+   configuration
 
 .. _jackson: https://github.com/FasterXML/jackson

akka-docs-dev/rst/java/http/routing-dsl/directives/index.rst

@@ -6,10 +6,10 @@ Directives
 A directive is a wrapper for a route or a list of alternative routes that adds one or more of the following
 functionality to its nested route(s):
 
- * it filters the request and lets only matching requests pass (e.g. the `get` directive lets only GET-requests pass)
- * it modifies the request or the ``RequestContext`` (e.g. the `path` directives filters on the unmatched path and then
-   passes an updated ``RequestContext`` unmatched path)
- * it modifies the response coming out of the nested route
+* it filters the request and lets only matching requests pass (e.g. the `get` directive lets only GET-requests pass)
+* it modifies the request or the ``RequestContext`` (e.g. the `path` directives filters on the unmatched path and then
+  passes an updated ``RequestContext`` unmatched path)
+* it modifies the response coming out of the nested route
 
 akka-http provides a set of predefined directives for various tasks. You can access them by either extending from
 ``akka.http.javadsl.server.AllDirectives`` or by importing them statically with
@@ -46,7 +46,7 @@ MethodDirectives
 MiscDirectives
   Contains directives that validate a request by user-defined logic.
 
-:ref:`PathDirectives-java`
+:ref:`path-directives-java`
   Contains directives to match and filter on the URI path of the incoming request.
 
 RangeDirectives

akka-docs-dev/rst/java/http/routing-dsl/directives/path-directives.rst

@@ -1,4 +1,4 @@
-.. _PathDirectives-java:
+.. _path-directives-java:
 
 PathDirectives
 ==============

akka-docs-dev/rst/java/http/routing-dsl/overview.rst

@@ -74,3 +74,27 @@ quickly without running them over the network and helps with writing assertions
 Read more about :ref:`http-testkit-java`.
 
 .. _DRY: http://en.wikipedia.org/wiki/Don%27t_repeat_yourself
+
+.. _handling-http-server-failures-high-level-scala:
+
+Handling HTTP Server failures in the High-Level API
+---------------------------------------------------
+There are various situations when failure may occur while initialising or running an Akka HTTP server.
+Akka by default will log all these failures, however sometimes one may want to react to failures in addition
+to them just being logged, for example by shutting down the actor system, or notifying some external monitoring
+end-point explicitly.
+
+Bind failures
+^^^^^^^^^^^^^
+For example the server might be unable to bind to the given port. For example when the port
+is already taken by another application, or if the port is privileged (i.e. only usable by ``root``).
+In this case the "binding future" will fail immediatly, and we can react to if by listening on the Future's completion:
+
+.. includecode:: ../../code/docs/http/javadsl/server/HighLevelServerBindFailureExample.java
+  :include: binding-failure-high-level-example
+
+
+.. note::
+  For a more low-level overview of the kinds of failures that can happen and also more fine-grained control over them
+  refer to the :ref:`handling-http-server-failures-low-level-java` documentation.
+

akka-docs-dev/rst/java/http/server-side/low-level-server-side-api.rst

@@ -93,9 +93,9 @@ this connection.
 
 Requests are handled by calling one of the ``handleWithXXX`` methods with a handler, which can either be
 
-  - a ``Flow<HttpRequest, HttpResponse, ?>`` for ``handleWith``,
-  - a function ``Function<HttpRequest, HttpResponse>`` for ``handleWithSyncHandler``,
-  - a function ``Function<HttpRequest, Future<HttpResponse>>`` for ``handleWithAsyncHandler``.
+- a ``Flow<HttpRequest, HttpResponse, ?>`` for ``handleWith``,
+- a function ``Function<HttpRequest, HttpResponse>`` for ``handleWithSyncHandler``,
+- a function ``Function<HttpRequest, Future<HttpResponse>>`` for ``handleWithAsyncHandler``.
 
 Here is a complete example:
 
@@ -165,4 +165,64 @@ that is a stage that "upgrades" a potentially encrypted raw connection to the HT
 
 You create an instance of the layer by calling one of the two overloads of the ``Http.get(system).serverLayer`` method,
 which also allows for varying degrees of configuration. Note, that the returned instance is not reusable and can only
-be materialized once.
+be materialized once.
+
+.. _handling-http-server-failures-low-level-java:
+
+Handling HTTP Server failures in the Low-Level API
+--------------------------------------------------
+
+There are various situations when failure may occur while initialising or running an Akka HTTP server.
+Akka by default will log all these failures, however sometimes one may want to react to failures in addition to them
+just being logged, for example by shutting down the actor system, or notifying some external monitoring end-point explicitly.
+
+There are multiple things that can fail when creating and materializing an HTTP Server (similarily, the same applied to
+a plain streaming ``Tcp`` server). The types of failures that can happen on different layers of the stack, starting
+from being unable to start the server, and ending with failing to unmarshal an HttpRequest, examples of failures include
+(from outer-most, to inner-most):
+
+- Failure to ``bind`` to the specified address/port,
+- Failure while accepting new ``IncommingConnection`` s, for example when the OS has run out of file descriptors or memory,
+- Failure while handling a connection, for example if the incoming ``HttpRequest`` is malformed.
+
+This section describes how to handle each failure situation, and in which situations these failures may occur.
+
+Bind failures
+^^^^^^^^^^^^^
+
+The first type of failure is when the server is unable to bind to the given port. For example when the port
+is already taken by another application, or if the port is privileged (i.e. only usable by ``root``).
+In this case the "binding future" will fail immediatly, and we can react to if by listening on the Future's completion:
+
+.. includecode:: ../../code/docs/http/javadsl/server/HttpServerExampleDocTest.java
+  :include: binding-failure-handling
+
+Once the server has successfully bound to a port, the ``Source<IncomingConnection, ?>`` starts running and emiting
+new incoming connections. This source technically can signal a failure as well, however this should only happen in very
+dramantic situations such as running out of file descriptors or memory available to the system, such that it's not able
+to accept a new incoming connection. Handling failures in Akka Streams is pretty stright forward, as failures are signaled
+through the stream starting from the stage which failed, all the way downstream to the final stages.
+
+Connections Source failures
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In the example below we add a custom ``PushStage`` (see :ref:`stream-customize-java`) in order to react to the
+stream's failure. We signal a ``failureMonitor`` actor with the cause why the stream is going down, and let the Actor
+handle the rest – maybe it'll decide to restart the server or shutdown the ActorSystem, that however is not our concern anymore.
+
+.. includecode:: ../../code/docs/http/javadsl/server/HttpServerExampleDocTest.java
+  :include: incoming-connections-source-failure-handling
+
+Connection failures
+^^^^^^^^^^^^^^^^^^^
+
+The third type of failure that can occur is when the connection has been properly established,
+however afterwards is terminated abruptly – for example by the client aborting the underlying TCP connection.
+To handle this failure we can use the same pattern as in the previous snippet, however apply it to the connection's Flow:
+
+.. includecode:: ../../code/docs/http/javadsl/server/HttpServerExampleDocTest.java
+  :include: connection-stream-failure-handling
+
+These failures can be described more or less infrastructure related, they are failing bindings or connections.
+Most of the time you won't need to dive into those very deeply, as Akka will simply log errors of this kind
+anyway, which is a reasonable default for such problems.

akka-docs-dev/rst/scala.rst

@@ -4,7 +4,7 @@ Scala Documentation
 ===================
 
 .. toctree::
-   :maxdepth: 2
+   :maxdepth: 3
 
    scala/stream-index
    scala/http/index

akka-docs-dev/rst/scala/code/docs/http/scaladsl/HttpServerExampleSpec.scala

@@ -3,20 +3,32 @@
  */
 
 package docs.http.scaladsl
-/*
-import scala.concurrent.Future
-import org.scalatest.{ WordSpec, Matchers }
-import akka.actor.ActorSystem
+
+import akka.actor.{ ActorRef, ActorSystem }
+import akka.event.LoggingAdapter
+import akka.http.scaladsl.Http
+import akka.http.scaladsl.Http.ServerBinding
+import akka.http.scaladsl.model._
+import akka.stream.ActorMaterializer
+import akka.stream.scaladsl.{ Flow, Sink }
+import akka.stream.stage.{ Context, PushStage }
+import org.scalatest.{ Matchers, WordSpec }
+
+import scala.concurrent.{ ExecutionContext, Future }
 
 class HttpServerExampleSpec extends WordSpec with Matchers {
 
+  // never actually called
+  val log: LoggingAdapter = null
+
   "binding-example" in {
+    import akka.http.scaladsl.Http
     import akka.stream.ActorMaterializer
     import akka.stream.scaladsl._
-    import akka.http.scaladsl.Http
 
     implicit val system = ActorSystem()
     implicit val materializer = ActorMaterializer()
+    implicit val ec = system.dispatcher
 
     val serverSource: Source[Http.IncomingConnection, Future[Http.ServerBinding]] =
       Http().bind(interface = "localhost", port = 8080)
@@ -27,12 +39,124 @@ class HttpServerExampleSpec extends WordSpec with Matchers {
       }).run()
   }
 
-  "full-server-example" in {
+  "binding-failure-high-level-example" in {
+    import akka.http.scaladsl.Http
+    import akka.http.scaladsl.server.Directives._
     import akka.stream.ActorMaterializer
-    import akka.stream.scaladsl.Sink
+
+    implicit val system = ActorSystem()
+    implicit val materializer = ActorMaterializer()
+    implicit val ec = system.dispatcher
+
+    val handler = get {
+      complete("Hello world!")
+    }
+
+    // let's say the OS won't allow us to bind to 80.
+    val (host, port) = ("localhost", 80)
+    val bindingFuture: Future[ServerBinding] =
+      Http().bindAndHandle(handler, host, port)
+
+    bindingFuture onFailure {
+      case ex: Exception =>
+        log.error(ex, "Failed to bind to {}:{}!", host, port)
+    }
+
+  }
+
+  // mock values:
+  val handleConnections: Sink[Http.IncomingConnection, Future[Http.ServerBinding]] =
+    Sink.ignore.mapMaterializedValue(_ => Future.failed(new Exception("")))
+
+  "binding-failure-handling" in {
+    implicit val system = ActorSystem()
+    implicit val materializer = ActorMaterializer()
+    implicit val ec = system.dispatcher
+
+    // let's say the OS won't allow us to bind to 80.
+    val (host, port) = ("localhost", 80)
+    val serverSource = Http().bind(host, port)
+
+    val bindingFuture: Future[ServerBinding] = serverSource
+      .to(handleConnections) // Sink[Http.IncomingConnection, _]
+      .run()
+
+    bindingFuture onFailure {
+      case ex: Exception =>
+        log.error(ex, "Failed to bind to {}:{}!", host, port)
+    }
+  }
+
+  "incoming-connections-source-failure-handling" in {
+    implicit val system = ActorSystem()
+    implicit val materializer = ActorMaterializer()
+    implicit val ec = system.dispatcher
+
+    import Http._
+    val (host, port) = ("localhost", 8080)
+    val serverSource = Http().bind(host, port)
+
+    val failureMonitor: ActorRef = ???
+
+    val reactToTopLevelFailures = Flow[IncomingConnection]
+      .transform { () =>
+        new PushStage[IncomingConnection, IncomingConnection] {
+          override def onPush(elem: IncomingConnection, ctx: Context[IncomingConnection]) =
+            ctx.push(elem)
+
+          override def onUpstreamFailure(cause: Throwable, ctx: Context[IncomingConnection]) = {
+            failureMonitor ! cause
+            super.onUpstreamFailure(cause, ctx)
+          }
+        }
+      }
+
+    serverSource
+      .via(reactToTopLevelFailures)
+      .to(handleConnections) // Sink[Http.IncomingConnection, _]
+      .run()
+  }
+
+  "connection-stream-failure-handling" in {
+    implicit val system = ActorSystem()
+    implicit val materializer = ActorMaterializer()
+    implicit val ec = system.dispatcher
+
+    val (host, port) = ("localhost", 8080)
+    val serverSource = Http().bind(host, port)
+
+    val reactToConnectionFailure = Flow[HttpRequest]
+      .transform { () =>
+        new PushStage[HttpRequest, HttpRequest] {
+          override def onPush(elem: HttpRequest, ctx: Context[HttpRequest]) =
+            ctx.push(elem)
+
+          override def onUpstreamFailure(cause: Throwable, ctx: Context[HttpRequest]) = {
+            // handle the failure somehow
+            super.onUpstreamFailure(cause, ctx)
+          }
+        }
+      }
+
+    val httpEcho = Flow[HttpRequest]
+      .via(reactToConnectionFailure)
+      .map { request =>
+        // simple text "echo" response:
+        HttpResponse(entity = HttpEntity(ContentTypes.`text/plain`, request.entity.dataBytes))
+      }
+
+    serverSource
+      .runForeach { con =>
+        con.handleWith(httpEcho)
+      }
+  }
+
+  "full-server-example" in {
     import akka.http.scaladsl.Http
     import akka.http.scaladsl.model.HttpMethods._
     import akka.http.scaladsl.model._
+    import akka.stream.ActorMaterializer
+    import akka.stream.scaladsl.Sink
 
     implicit val system = ActorSystem()
     implicit val materializer = ActorMaterializer()
@@ -65,10 +189,10 @@ class HttpServerExampleSpec extends WordSpec with Matchers {
   }
 
   "low-level-server-example" in {
-    import akka.stream.ActorMaterializer
     import akka.http.scaladsl.Http
     import akka.http.scaladsl.model.HttpMethods._
     import akka.http.scaladsl.model._
+    import akka.stream.ActorMaterializer
 
     implicit val system = ActorSystem()
     implicit val materializer = ActorMaterializer()
@@ -94,10 +218,10 @@ class HttpServerExampleSpec extends WordSpec with Matchers {
   // format: OFF
 
   "high-level-server-example" in {
-    import akka.stream.ActorMaterializer
     import akka.http.scaladsl.Http
-    import akka.http.scaladsl.server.Directives._
     import akka.http.scaladsl.marshallers.xml.ScalaXmlSupport._
+    import akka.http.scaladsl.server.Directives._
+    import akka.stream.ActorMaterializer
 
     implicit val system = ActorSystem()
     implicit val materializer = ActorMaterializer()
@@ -124,14 +248,15 @@ class HttpServerExampleSpec extends WordSpec with Matchers {
   }
 
   "minimal-routing-example" in {
-    import akka.stream.ActorMaterializer
     import akka.http.scaladsl.Http
-    import akka.http.scaladsl.server.Directives._
     import akka.http.scaladsl.marshallers.xml.ScalaXmlSupport._
+    import akka.http.scaladsl.server.Directives._
+    import akka.stream.ActorMaterializer
 
     object Main extends App {
       implicit val system = ActorSystem("my-system")
       implicit val materializer = ActorMaterializer()
+      implicit val ec = system.dispatcher
 
       val route =
         path("hello") {
@@ -145,9 +270,7 @@ class HttpServerExampleSpec extends WordSpec with Matchers {
       val bindingFuture = Http().bindAndHandle(route, "localhost", 8080)
 
       println(s"Server online at http://localhost:8080/\nPress RETURN to stop...")
-      Console.readLine()
-
-      import system.dispatcher // for the future transformations
+      Console.readLine() // for the future transformations
       bindingFuture
         .flatMap(_.unbind()) // trigger unbinding from the port
         .onComplete(_ ⇒ system.shutdown()) // and shutdown when done
@@ -156,13 +279,13 @@ class HttpServerExampleSpec extends WordSpec with Matchers {
 
   "long-routing-example" in {
     import akka.actor.ActorRef
-    import akka.util.Timeout
-    import akka.pattern.ask
-    import akka.http.scaladsl.marshalling.ToResponseMarshaller
-    import akka.http.scaladsl.unmarshalling.FromRequestUnmarshaller
-    import akka.http.scaladsl.model.StatusCodes.MovedPermanently
     import akka.http.scaladsl.coding.Deflate
+    import akka.http.scaladsl.marshalling.ToResponseMarshaller
+    import akka.http.scaladsl.model.StatusCodes.MovedPermanently
     import akka.http.scaladsl.server.Directives._
+    import akka.http.scaladsl.unmarshalling.FromRequestUnmarshaller
+    import akka.pattern.ask
+    import akka.util.Timeout
 
     // types used by the API routes
     type Money = Double // only for demo purposes, don't try this at home!
@@ -174,6 +297,9 @@ class HttpServerExampleSpec extends WordSpec with Matchers {
     implicit val orderUM: FromRequestUnmarshaller[Order] = ???
     implicit val orderM: ToResponseMarshaller[Seq[Order]] = ???
     implicit val timeout: Timeout = ??? // for actor asks
+    implicit val ec: ExecutionContext = ???
+    implicit val mat: ActorMaterializer = ???
+    implicit val sys: ActorSystem = ???
 
     val route = {
       path("orders") {
@@ -255,4 +381,3 @@ class HttpServerExampleSpec extends WordSpec with Matchers {
     def processOrderRequest(id: Int, complete: Order => Unit): Unit = ???
   }
 }
-*/

akka-docs-dev/rst/scala/code/docs/stream/io/StreamTcpDocSpec.scala

@@ -3,19 +3,15 @@
  */
 package docs.stream.io
 
-import java.net.InetSocketAddress
 import java.util.concurrent.atomic.AtomicReference
 
 import akka.stream._
 import akka.stream.scaladsl.Tcp._
 import akka.stream.scaladsl._
-import akka.stream.stage.Context
-import akka.stream.stage.PushStage
-import akka.stream.stage.SyncDirective
+import akka.stream.stage.{ Context, PushStage, SyncDirective }
 import akka.stream.testkit.AkkaSpec
 import akka.testkit.TestProbe
 import akka.util.ByteString
-import docs.stream.cookbook.RecipeParseLines
 import docs.utils.TestUtils
 
 import scala.concurrent.Future
@@ -31,8 +27,14 @@ class StreamTcpDocSpec extends AkkaSpec {
   "simple server connection" in {
     {
       //#echo-server-simple-bind
-      val connections: Source[IncomingConnection, Future[ServerBinding]] =
-        Tcp().bind("127.0.0.1", 8888)
+      val binding: Future[ServerBinding] =
+        Tcp().bind("127.0.0.1", 8888).to(Sink.ignore).run()
+
+      binding.map { b =>
+        b.unbind() onComplete {
+          case _ => // ...
+        }
+      }
       //#echo-server-simple-bind
     }
     {

akka-docs-dev/rst/scala/http/low-level-server-side-api.rst

@@ -167,4 +167,68 @@ On the server-side the stand-alone HTTP layer forms a ``BidiFlow`` that is defin
    :snippet: server-layer
 
 You create an instance of ``Http.ServerLayer`` by calling one of the two overloads of the ``Http().serverLayer`` method,
-which also allows for varying degrees of configuration.
+which also allows for varying degrees of configuration.
+
+.. _handling-http-server-failures-low-level-scala:
+
+Handling HTTP Server failures in the Low-Level API
+--------------------------------------------------
+
+There are various situations when failure may occur while initialising or running an Akka HTTP server.
+Akka by default will log all these failures, however sometimes one may want to react to failures in addition to them
+just being logged, for example by shutting down the actor system, or notifying some external monitoring end-point explicitly.
+
+There are multiple things that can fail when creating and materializing an HTTP Server (similarily, the same applied to
+a plain streaming ``Tcp()`` server). The types of failures that can happen on different layers of the stack, starting
+from being unable to start the server, and ending with failing to unmarshal an HttpRequest, examples of failures include
+(from outer-most, to inner-most):
+
+- Failure to ``bind`` to the specified address/port,
+- Failure while accepting new ``IncommingConnection`` s, for example when the OS has run out of file descriptors or memory,
+- Failure while handling a connection, for example if the incoming ``HttpRequest`` is malformed.
+
+This section describes how to handle each failure situation, and in which situations these failures may occur.
+
+Bind failures
+^^^^^^^^^^^^^
+
+The first type of failure is when the server is unable to bind to the given port. For example when the port
+is already taken by another application, or if the port is privileged (i.e. only usable by ``root``).
+In this case the "binding future" will fail immediatly, and we can react to if by listening on the Future's completion:
+
+.. includecode2:: ../code/docs/http/scaladsl/HttpServerExampleSpec.scala
+  :snippet: binding-failure-handling
+
+Once the server has successfully bound to a port, the ``Source[IncomingConnection, _]`` starts running and emiting
+new incoming connections. This source technically can signal a failure as well, however this should only happen in very
+dramantic situations such as running out of file descriptors or memory available to the system, such that it's not able
+to accept a new incoming connection. Handling failures in Akka Streams is pretty stright forward, as failures are signaled
+through the stream starting from the stage which failed, all the way downstream to the final stages.
+
+Connections Source failures
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In the example below we add a custom ``PushStage`` (see :ref:`stream-customize-scala`) in order to react to the
+stream's failure. We signal a ``failureMonitor`` actor with the cause why the stream is going down, and let the Actor
+handle the rest – maybe it'll decide to restart the server or shutdown the ActorSystem, that however is not our concern anymore.
+
+.. includecode2:: ../code/docs/http/scaladsl/HttpServerExampleSpec.scala
+  :snippet: incoming-connections-source-failure-handling
+
+Connection failures
+^^^^^^^^^^^^^^^^^^^
+
+The third type of failure that can occur is when the connection has been properly established,
+however afterwards is terminated abruptly – for example by the client aborting the underlying TCP connection.
+To handle this failure we can use the same pattern as in the previous snippet, however apply it to the connection's Flow:
+
+.. includecode2:: ../code/docs/http/scaladsl/HttpServerExampleSpec.scala
+  :snippet: connection-stream-failure-handling
+
+These failures can be described more or less infrastructure related, they are failing bindings or connections.
+Most of the time you won't need to dive into those very deeply, as Akka will simply log errors of this kind
+anyway, which is a reasonable default for such problems.
+
+In order to learn more about handling exceptions in the actual routing layer, which is where your application code
+comes into the picture, refer to :ref:`exception-handling-scala` which focuses explicitly on explaining how exceptions
+thrown in routes can be handled and transformed into :class:`HttpResponse` s with apropriate error codes and human-readable failure descriptions.

akka-docs-dev/rst/scala/http/routing-dsl/directives/execution-directives/handleExceptions.rst

@@ -17,7 +17,7 @@ Description
 Using this directive is an alternative to using a global implicitly defined ``ExceptionHandler`` that
 applies to the complete route.
 
-See :ref:`Exception Handling` for general information about options for handling exceptions.
+See :ref:`exception-handling-scala` for general information about options for handling exceptions.
 
 Example
 -------

akka-docs-dev/rst/scala/http/routing-dsl/directives/route-directives/failWith.rst

@@ -4,7 +4,7 @@ failWith
 ========
 
 Bubbles up the given error through the route structure where it is dealt with by the closest ``handleExceptions``
-directive and its ``ExceptionHandler``.
+directive and its :class:`ExceptionHandler`.
 
 
 Signature
@@ -19,12 +19,12 @@ Description
 
 ``failWith`` explicitly raises an exception that gets bubbled up through the route structure to be picked up by the
 nearest ``handleExceptions`` directive. Using ``failWith`` rather than simply throwing an exception enables the route
-structure's :ref:`Exception Handling` mechanism to deal with the exception even if the current route is executed
+structure's :ref:`exception-handling-scala` mechanism to deal with the exception even if the current route is executed
 asynchronously on another thread (e.g. in a ``Future`` or separate actor).
 
 If no ``handleExceptions`` is present above the respective location in the
 route structure the top-level routing logic will handle the exception and translate it into a corresponding
-``HttpResponse`` using the in-scope ``ExceptionHandler`` (see also the :ref:`Exception Handling` chapter).
+``HttpResponse`` using the in-scope ``ExceptionHandler`` (see also the :ref:`exception-handling-scala` chapter).
 
 There is one notable special case: If the given exception is a ``RejectionError`` exception it is *not* bubbled up,
 but rather the wrapped exception is unpacked and "executed". This allows the "tunneling" of a rejection via an

akka-docs-dev/rst/scala/http/routing-dsl/exception-handling.rst

@@ -1,4 +1,4 @@
-.. _Exception Handling:
+.. _exception-handling-scala:
 
 Exception Handling
 ==================

akka-docs-dev/rst/scala/http/routing-dsl/index.rst

@@ -43,4 +43,34 @@ not really do anything useful but its definition should give you a feel for what
 the Routing DSL will look like:
 
 .. includecode2:: ../../code/docs/http/scaladsl/HttpServerExampleSpec.scala
-   :snippet: long-routing-example
+   :snippet: long-routing-example
+
+.. _handling-http-server-failures-high-level-scala:
+
+Handling HTTP Server failures in the High-Level API
+---------------------------------------------------
+There are various situations when failure may occur while initialising or running an Akka HTTP server.
+Akka by default will log all these failures, however sometimes one may want to react to failures in addition
+to them just being logged, for example by shutting down the actor system, or notifying some external monitoring
+end-point explicitly.
+
+Bind failures
+^^^^^^^^^^^^^
+For example the server might be unable to bind to the given port. For example when the port
+is already taken by another application, or if the port is privileged (i.e. only usable by ``root``).
+In this case the "binding future" will fail immediatly, and we can react to if by listening on the Future's completion:
+
+.. includecode2:: ../../code/docs/http/scaladsl/HttpServerExampleSpec.scala
+  :snippet: binding-failure-high-level-example
+
+
+.. note::
+  For a more low-level overview of the kinds of failures that can happen and also more fine-grained control over them
+  refer to the :ref:`handling-http-server-failures-low-level-scala` documentation.
+
+Failures and exceptions inside the Routing DSL
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Exception handling within the Routing DSL is done by providing :class:`ExceptionHandler` s which are documented in-depth
+in the :ref:`exception-handling-scala` section of the documtnation. You can use them to transform exceptions into
+:class:`HttpResponse` s with apropriate error codes and human-readable failure descriptions.

akka-docs-dev/rst/scala/http/routing-dsl/routes.rst

@@ -14,7 +14,7 @@ Generally when a route receives a request (or rather a ``RequestContext`` for it
 
 - Complete the request by returning the value of ``requestContext.complete(...)``
 - Reject the request by returning the value of ``requestContext.reject(...)`` (see :ref:`Rejections`)
-- Fail the request by returning the value of ``requestContext.fail(...)`` or by just throwing an exception (see :ref:`Exception Handling`)
+- Fail the request by returning the value of ``requestContext.fail(...)`` or by just throwing an exception (see :ref:`exception-handling-scala`)
 - Do any kind of asynchronous processing and instantly return a ``Future[RouteResult]`` to be eventually completed later
 
 The first case is pretty clear, by calling ``complete`` a given response is sent to the client as reaction to the

akka-http-core/src/main/java/akka/http/javadsl/model/HttpEntities.java

@@ -7,8 +7,8 @@ package akka.http.javadsl.model;
 import java.io.File;
 
 import akka.http.impl.util.JavaAccessors;
-import akka.http.scaladsl.model.*;
 import akka.http.scaladsl.model.HttpEntity;
+import akka.http.scaladsl.model.HttpEntity$;
 import akka.util.ByteString;
 import akka.stream.javadsl.Source;
 

akka-http-core/src/main/java/akka/http/javadsl/model/HttpMessage.java

@@ -5,6 +5,7 @@
 package akka.http.javadsl.model;
 
 import akka.japi.Option;
+import akka.stream.javadsl.Source;
 import akka.util.ByteString;
 
 import java.io.File;