Surface fatal exceptions that stop the event loop

- Request an app Shutdown so KestrelEngine gets disposed
- Ensure Listener.Dispose doesn't deadlock before the engine
  can be disposed
- Rely on the existing logic to rethrow in the fatal error when
  the engine gets disposed

src/Kestrel/ServerFactory.cs

@@ -18,10 +18,12 @@ namespace Kestrel
     public class ServerFactory : IServerFactory
     {
         private readonly ILibraryManager _libraryManager;
+        private readonly IApplicationShutdown _appShutdownService;
 
-        public ServerFactory(ILibraryManager libraryManager)
+        public ServerFactory(ILibraryManager libraryManager, IApplicationShutdown appShutdownService)
         {
             _libraryManager = libraryManager;
+            _appShutdownService = appShutdownService;
         }
 
         public IServerInformation Initialize(IConfiguration configuration)
@@ -35,7 +37,7 @@ namespace Kestrel
         {
             var disposables = new List<IDisposable>();
             var information = (ServerInformation)serverInformation;
-            var engine = new KestrelEngine(_libraryManager);
+            var engine = new KestrelEngine(_libraryManager, _appShutdownService);
             engine.Start(1);
             foreach (var address in information.Addresses)
             {

src/Microsoft.AspNet.Server.Kestrel/Http/Listener.cs

@@ -76,22 +76,32 @@ namespace Microsoft.AspNet.Server.Kestrel.Http
 
         public void Dispose()
         {
-            var tcs = new TaskCompletionSource<int>();
-            Thread.Post(
-                _ =>
-                {
-                    try
+            // Ensure the event loop is still running.
+            // If the event loop isn't running and we try to wait on this Post
+            // to complete, then KestrelEngine will never be disposed and
+            // the exception that stopped the event loop will never be surfaced.
+            if (Thread.FatalError == null)
+            {
+                var tcs = new TaskCompletionSource<int>();
+                Thread.Post(
+                    _ =>
                     {
-                        ListenSocket.Dispose();
-                        tcs.SetResult(0);
-                    }
-                    catch (Exception ex)
-                    {
-                        tcs.SetException(ex);
-                    }
-                },
-                null);
-            tcs.Task.Wait();
+                        try
+                        {
+                            ListenSocket.Dispose();
+                            tcs.SetResult(0);
+                        }
+                        catch (Exception ex)
+                        {
+                            tcs.SetException(ex);
+                        }
+                    },
+                    null);
+
+                // REVIEW: Should we add a timeout here to be safe?
+                tcs.Task.Wait();
+            }
+
             ListenSocket = null;
         }
     }

src/Microsoft.AspNet.Server.Kestrel/Infrastructure/KestrelThread.cs

@@ -38,6 +38,7 @@ namespace Microsoft.AspNet.Server.Kestrel
         }
 
         public UvLoopHandle Loop { get { return _loop; } }
+        public ExceptionDispatchInfo FatalError { get { return _closeError; } }
 
         public Action<Action<IntPtr>, IntPtr> QueueCloseHandle { get; internal set; }
 
@@ -173,6 +174,9 @@ namespace Microsoft.AspNet.Server.Kestrel
             catch (Exception ex)
             {
                 _closeError = ExceptionDispatchInfo.Capture(ex);
+                // Request shutdown so we can rethrow this exception
+                // in Stop which should be observable.
+                _engine.AppShutdown.RequestShutdown();
             }
         }
 

src/Microsoft.AspNet.Server.Kestrel/KestrelEngine.cs

@@ -13,9 +13,9 @@ namespace Microsoft.AspNet.Server.Kestrel
 {
     public class KestrelEngine : IDisposable
     {
-
-        public KestrelEngine(ILibraryManager libraryManager)
+        public KestrelEngine(ILibraryManager libraryManager, IApplicationShutdown appShutdownService)
         {
+            AppShutdown = appShutdownService;
             Threads = new List<KestrelThread>();
             Listeners = new List<Listener>();
             Memory = new MemoryPool();
@@ -63,6 +63,7 @@ namespace Microsoft.AspNet.Server.Kestrel
 
         public Libuv Libuv { get; private set; }
         public IMemoryPool Memory { get; set; }
+        public IApplicationShutdown AppShutdown { get; private set; }
         public List<KestrelThread> Threads { get; private set; }
         public List<Listener> Listeners { get; private set; }
 

test/Microsoft.AspNet.Server.KestrelTests/EngineTests.cs

@@ -78,7 +78,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
         [Fact]
         public async Task EngineCanStartAndStop()
         {
-            var engine = new KestrelEngine(LibraryManager);
+            var engine = new KestrelEngine(LibraryManager, new ShutdownNotImplemented());
             engine.Start(1);
             engine.Dispose();
         }
@@ -86,7 +86,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
         [Fact]
         public async Task ListenerCanCreateAndDispose()
         {
-            var engine = new KestrelEngine(LibraryManager);
+            var engine = new KestrelEngine(LibraryManager, new ShutdownNotImplemented());
             engine.Start(1);
             var started = engine.CreateServer("http", "localhost", 54321, App);
             started.Dispose();
@@ -97,7 +97,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
         [Fact]
         public async Task ConnectionCanReadAndWrite()
         {
-            var engine = new KestrelEngine(LibraryManager);
+            var engine = new KestrelEngine(LibraryManager, new ShutdownNotImplemented());
             engine.Start(1);
             var started = engine.CreateServer("http", "localhost", 54321, App);
 

test/Microsoft.AspNet.Server.KestrelTests/NetworkingTests.cs

@@ -22,7 +22,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
         Libuv _uv;
         public NetworkingTests()
         {
-            var engine = new KestrelEngine(LibraryManager);
+            var engine = new KestrelEngine(LibraryManager, new ShutdownNotImplemented());
             _uv = engine.Libuv;
         }
 

test/Microsoft.AspNet.Server.KestrelTests/ShutdownNotImplemented.cs

@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Threading;
+using Microsoft.Framework.Runtime;
+
+namespace Microsoft.AspNet.Server.KestrelTests
+{
+    public class ShutdownNotImplemented : IApplicationShutdown
+    {
+        public CancellationToken ShutdownRequested
+        {
+            get
+            {
+                throw new NotImplementedException();
+            }
+        }
+
+        public void RequestShutdown()
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

test/Microsoft.AspNet.Server.KestrelTests/TestServer.cs

@@ -45,7 +45,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
 
         public void Create(Func<Frame, Task> app)
         {
-            _engine = new KestrelEngine(LibraryManager);
+            _engine = new KestrelEngine(LibraryManager, new ShutdownNotImplemented());
             _engine.Start(1);
             _server = _engine.CreateServer(
                 "http",