#947 Add IServer.StopAsyc, IWebHost.StopAsync, and make Start async

samples/SampleStartups/StartupExternallyControlled.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
@@ -34,8 +36,9 @@ namespace SampleStartups
                 .Start(_urls.ToArray());
         }
 
-        public void Stop()
+        public async Task StopAsync()
         {
+            await _host.StopAsync(TimeSpan.FromSeconds(5));
             _host.Dispose();
         }
 

src/Microsoft.AspNetCore.Hosting.Abstractions/HostingAbstractionsWebHostBuilderExtensions.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
@@ -166,7 +168,7 @@ namespace Microsoft.AspNetCore.Hosting
         public static IWebHost Start(this IWebHostBuilder hostBuilder, params string[] urls)
         {
             var host = hostBuilder.UseUrls(urls).Build();
-            host.Start();
+            host.StartAsync(CancellationToken.None).GetAwaiter().GetResult();
             return host;
         }
     }

src/Microsoft.AspNetCore.Hosting.Abstractions/IWebHost.cs

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Features;
 
 namespace Microsoft.AspNetCore.Hosting
@@ -24,6 +26,13 @@ namespace Microsoft.AspNetCore.Hosting
         /// <summary>
         /// Starts listening on the configured addresses.
         /// </summary>
-        void Start();
+        Task StartAsync(CancellationToken cancellationToken);
+
+        /// <summary>
+        /// Attempt to gracefully stop the host.
+        /// </summary>
+        /// <param name="cancellationToken"></param>
+        /// <returns></returns>
+        Task StopAsync(CancellationToken cancellationToken);
     }
 }

src/Microsoft.AspNetCore.Hosting.Abstractions/WebHostDefaults.cs

@@ -16,5 +16,7 @@ namespace Microsoft.AspNetCore.Hosting
         public static readonly string ServerUrlsKey = "urls";
         public static readonly string ContentRootKey = "contentRoot";
         public static readonly string PreferHostingUrls = "preferHostingUrls";
+
+        public static readonly string ShutdownTimeoutKey = "shutdownTimeoutSeconds";
     }
 }

src/Microsoft.AspNetCore.Hosting.Abstractions/exceptions.net45.json

@@ -16,5 +16,24 @@
     "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHostBuilder",
     "NewMemberId": "Microsoft.AspNetCore.Hosting.IWebHostBuilder ConfigureConfiguration(System.Action<Microsoft.AspNetCore.Hosting.WebHostBuilderContext, Microsoft.Extensions.Configuration.IConfigurationBuilder> configureDelegate)",
     "Kind": "Addition"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "OldMemberId": "System.Void Start()",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StartAsync(System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Modification"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StartAsync(System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Addition"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StopAsync(System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Addition"
   }
 ]

src/Microsoft.AspNetCore.Hosting.Abstractions/exceptions.netcore.json

@@ -16,5 +16,24 @@
     "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHostBuilder",
     "NewMemberId": "Microsoft.AspNetCore.Hosting.IWebHostBuilder ConfigureConfiguration(System.Action<Microsoft.AspNetCore.Hosting.WebHostBuilderContext, Microsoft.Extensions.Configuration.IConfigurationBuilder> configureDelegate)",
     "Kind": "Addition"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "OldMemberId": "System.Void Start()",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StartAsync(System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Modification"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StartAsync(System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Addition"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.IWebHost : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StopAsync(System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Addition"
   }
 ]

src/Microsoft.AspNetCore.Hosting.Server.Abstractions/IServer.cs

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http.Features;
 
 namespace Microsoft.AspNetCore.Hosting.Server
@@ -21,6 +23,13 @@ namespace Microsoft.AspNetCore.Hosting.Server
         /// </summary>
         /// <param name="application">An instance of <see cref="IHttpApplication{TContext}"/>.</param>
         /// <typeparam name="TContext">The context associated with the application.</typeparam>
-        void Start<TContext>(IHttpApplication<TContext> application);
+        /// <param name="cancellationToken">Indicates if the server startup should be aborted.</param>
+        Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken);
+
+        /// <summary>
+        /// Stop processing requests and shut down the server, gracefully if possible.
+        /// </summary>
+        /// <param name="cancellationToken">Indicates if the graceful shutdown should be aborted.</param>
+        Task StopAsync(CancellationToken cancellationToken);
     }
 }

src/Microsoft.AspNetCore.Hosting.Server.Abstractions/exceptions.net45.json

@@ -10,5 +10,24 @@
     "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.Features.IServerAddressesFeature",
     "NewMemberId": "System.Void set_PreferHostingUrls(System.Boolean value)",
     "Kind": "Addition"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "OldMemberId": "System.Void Start<T0>(Microsoft.AspNetCore.Hosting.Server.IHttpApplication<T0> application)",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StartAsync<T0>(Microsoft.AspNetCore.Hosting.Server.IHttpApplication<T0> application, System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Modification"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StartAsync<T0>(Microsoft.AspNetCore.Hosting.Server.IHttpApplication<T0> application, System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Addition"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StopAsync(System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Addition"
   }
 ]

src/Microsoft.AspNetCore.Hosting.Server.Abstractions/exceptions.netcore.json

@@ -10,5 +10,24 @@
     "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.Features.IServerAddressesFeature",
     "NewMemberId": "System.Void set_PreferHostingUrls(System.Boolean value)",
     "Kind": "Addition"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "OldMemberId": "System.Void Start<T0>(Microsoft.AspNetCore.Hosting.Server.IHttpApplication<T0> application)",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StartAsync<T0>(Microsoft.AspNetCore.Hosting.Server.IHttpApplication<T0> application, System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Modification"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StartAsync<T0>(Microsoft.AspNetCore.Hosting.Server.IHttpApplication<T0> application, System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Addition"
+  },
+  {
+    "OldTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewTypeId": "public interface Microsoft.AspNetCore.Hosting.Server.IServer : System.IDisposable",
+    "NewMemberId": "System.Threading.Tasks.Task StopAsync(System.Threading.CancellationToken cancellationToken)",
+    "Kind": "Addition"
   }
 ]

src/Microsoft.AspNetCore.Hosting/Internal/HostingLoggerExtensions.cs

@@ -82,6 +82,16 @@ namespace Microsoft.AspNetCore.Hosting.Internal
             }
         }
 
+        public static void ServerShutdownException(this ILogger logger, Exception ex)
+        {
+            if (logger.IsEnabled(LogLevel.Debug))
+            {
+                logger.LogDebug(
+                    eventId: LoggerEventIds.ServerShutdownException,
+                    exception: ex,
+                    message: "Server shutdown exception");
+            }
+        }
 
         private class HostingLogScope : IReadOnlyList<KeyValuePair<string, object>>
         {

src/Microsoft.AspNetCore.Hosting/Internal/LoggerEventIds.cs

@@ -16,5 +16,6 @@ namespace Microsoft.AspNetCore.Hosting.Internal
         public const int HostedServiceStartException = 9;
         public const int HostedServiceStopException = 10;
         public const int HostingStartupAssemblyException = 11;
+        public const int ServerShutdownException = 12;
     }
 }

src/Microsoft.AspNetCore.Hosting/Internal/WebHost.cs

@@ -7,6 +7,8 @@ using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.InteropServices;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting.Builder;
 using Microsoft.AspNetCore.Hosting.Server;
@@ -39,6 +41,8 @@ namespace Microsoft.AspNetCore.Hosting.Internal
         private RequestDelegate _application;
         private ILogger<WebHost> _logger;
 
+        private bool _stopped;
+
         // Used for testing only
         internal WebHostOptions Options => _options;
 
@@ -100,7 +104,7 @@ namespace Microsoft.AspNetCore.Hosting.Internal
             }
         }
 
-        public virtual void Start()
+        public virtual async Task StartAsync(CancellationToken cancellationToken)
         {
             HostingEventSource.Log.HostStart();
             _logger = _applicationServices.GetRequiredService<ILogger<WebHost>>();
@@ -112,7 +116,8 @@ namespace Microsoft.AspNetCore.Hosting.Internal
             _hostedServiceExecutor = _applicationServices.GetRequiredService<HostedServiceExecutor>();
             var diagnosticSource = _applicationServices.GetRequiredService<DiagnosticListener>();
             var httpContextFactory = _applicationServices.GetRequiredService<IHttpContextFactory>();
-            Server.Start(new HostingApplication(_application, _logger, diagnosticSource, httpContextFactory));
+            var hostingApp = new HostingApplication(_application, _logger, diagnosticSource, httpContextFactory);
+            await Server.StartAsync(hostingApp, cancellationToken);
 
             // Fire IApplicationLifetime.Started
             _applicationLifetime?.NotifyStarted();
@@ -267,23 +272,51 @@ namespace Microsoft.AspNetCore.Hosting.Internal
             }
         }
 
-        public void Dispose()
+        public async Task StopAsync(CancellationToken cancellationToken)
         {
+            if (_stopped)
+            {
+                return;
+            }
+            _stopped = true;
+
             _logger?.Shutdown();
 
+            if (!cancellationToken.CanBeCanceled)
+            {
+                cancellationToken = new CancellationTokenSource(Options.ShutdownTimeout).Token;
+            }
+
             // Fire IApplicationLifetime.Stopping
             _applicationLifetime?.StopApplication();
 
+            await Server?.StopAsync(cancellationToken);
+
             // Fire the IHostedService.Stop
             _hostedServiceExecutor?.Stop();
 
-            (_hostingServiceProvider as IDisposable)?.Dispose();
-            (_applicationServices as IDisposable)?.Dispose();
-
             // Fire IApplicationLifetime.Stopped
             _applicationLifetime?.NotifyStopped();
 
             HostingEventSource.Log.HostStop();
         }
+
+        public void Dispose()
+        {
+            if (!_stopped)
+            {
+                try
+                {
+                    this.StopAsync().GetAwaiter().GetResult();
+                }
+                catch (Exception ex)
+                {
+                    _logger?.ServerShutdownException(ex);
+                }
+            }
+
+            (_applicationServices as IDisposable)?.Dispose();
+            (_hostingServiceProvider as IDisposable)?.Dispose();
+        }
     }
 }

src/Microsoft.AspNetCore.Hosting/Internal/WebHostOptions.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using Microsoft.Extensions.Configuration;
 
 namespace Microsoft.AspNetCore.Hosting.Internal
@@ -27,6 +28,13 @@ namespace Microsoft.AspNetCore.Hosting.Internal
             ContentRootPath = configuration[WebHostDefaults.ContentRootKey];
             HostingStartupAssemblies = configuration[WebHostDefaults.HostingStartupAssembliesKey]?.Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries) ?? new string[0];
             PreferHostingUrls = ParseBool(configuration, WebHostDefaults.PreferHostingUrls);
+
+            var timeout = configuration[WebHostDefaults.ShutdownTimeoutKey];
+            if (!string.IsNullOrEmpty(timeout)
+                && int.TryParse(timeout, NumberStyles.None, CultureInfo.InvariantCulture, out var seconds))
+            {
+                ShutdownTimeout = TimeSpan.FromSeconds(seconds);
+            }
         }
 
         public string ApplicationName { get; set; }
@@ -47,6 +55,8 @@ namespace Microsoft.AspNetCore.Hosting.Internal
 
         public bool PreferHostingUrls { get; set; }
 
+        public TimeSpan ShutdownTimeout { get; set; } = TimeSpan.FromSeconds(5);
+
         private static bool ParseBool(IConfiguration configuration, string key)
         {
             return string.Equals("true", configuration[key], StringComparison.OrdinalIgnoreCase)

src/Microsoft.AspNetCore.Hosting/WebHostExtensions.cs

@@ -7,6 +7,7 @@ using System.Reflection;
 using System.Runtime.Loader;
 #endif
 using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting.Server.Features;
 using Microsoft.Extensions.DependencyInjection;
 
@@ -14,11 +15,62 @@ namespace Microsoft.AspNetCore.Hosting
 {
     public static class WebHostExtensions
     {
+        /// <summary>
+        /// Starts the host.
+        /// </summary>
+        /// <param name="host"></param>
+        /// <returns></returns>
+        public static void Start(this IWebHost host)
+        {
+            host.StartAsync().GetAwaiter().GetResult();
+        }
+
+        /// <summary>
+        /// Starts the host.
+        /// </summary>
+        /// <param name="host"></param>
+        /// <returns></returns>
+        public static Task StartAsync(this IWebHost host)
+        {
+            return host.StartAsync(CancellationToken.None);
+        }
+
+        /// <summary>
+        /// Gracefully stops the host.
+        /// </summary>
+        /// <param name="host"></param>
+        /// <returns></returns>
+        public static Task StopAsync(this IWebHost host)
+        {
+            return host.StopAsync(CancellationToken.None);
+        }
+
+        /// <summary>
+        /// Attempts to gracefully stop the host with the given timeout.
+        /// </summary>
+        /// <param name="host"></param>
+        /// <param name="timeout">The timeout for stopping gracefully. Once expired the
+        /// server may terminate any remaining active connections.</param>
+        /// <returns></returns>
+        public static Task StopAsync(this IWebHost host, TimeSpan timeout)
+        {
+            return host.StopAsync(new CancellationTokenSource(timeout).Token);
+        }
+
         /// <summary>
         /// Runs a web application and block the calling thread until host shutdown.
         /// </summary>
         /// <param name="host">The <see cref="IWebHost"/> to run.</param>
         public static void Run(this IWebHost host)
+        {
+            host.RunAsync().GetAwaiter().GetResult();
+        }
+
+        /// <summary>
+        /// Runs a web application and returns a Task that only completes on host shutdown.
+        /// </summary>
+        /// <param name="host">The <see cref="IWebHost"/> to run.</param>
+        public static async Task RunAsync(this IWebHost host)
         {
             var done = new ManualResetEventSlim(false);
             using (var cts = new CancellationTokenSource())
@@ -28,7 +80,13 @@ namespace Microsoft.AspNetCore.Hosting
                     if (!cts.IsCancellationRequested)
                     {
                         Console.WriteLine("Application is shutting down...");
-                        cts.Cancel();
+                        try
+                        {
+                            cts.Cancel();
+                        }
+                        catch (ObjectDisposedException)
+                        {
+                        }
                     }
 
                     done.Wait();
@@ -48,26 +106,26 @@ namespace Microsoft.AspNetCore.Hosting
                     eventArgs.Cancel = true;
                 };
 
-                host.Run(cts.Token, "Application started. Press Ctrl+C to shut down.");
+                await host.RunAsync(cts.Token, "Application started. Press Ctrl+C to shut down.");
                 done.Set();
             }
         }
 
         /// <summary>
-        /// Runs a web application and block the calling thread until token is triggered or shutdown is triggered.
+        /// Runs a web application and and returns a Task that only completes when the token is triggered or shutdown is triggered.
         /// </summary>
         /// <param name="host">The <see cref="IWebHost"/> to run.</param>
         /// <param name="token">The token to trigger shutdown.</param>
-        public static void Run(this IWebHost host, CancellationToken token)
+        public static Task RunAsync(this IWebHost host, CancellationToken token)
         {
-            host.Run(token, shutdownMessage: null);
+            return host.RunAsync(token, shutdownMessage: null);
         }
 
-        private static void Run(this IWebHost host, CancellationToken token, string shutdownMessage)
+        private static async Task RunAsync(this IWebHost host, CancellationToken token, string shutdownMessage)
         {
             using (host)
             {
-                host.Start();
+                await host.StartAsync(token);
 
                 var hostingEnvironment = host.Services.GetService<IHostingEnvironment>();
                 var applicationLifetime = host.Services.GetService<IApplicationLifetime>();
@@ -95,7 +153,17 @@ namespace Microsoft.AspNetCore.Hosting
                 },
                 applicationLifetime);
 
-                applicationLifetime.ApplicationStopping.WaitHandle.WaitOne();
+                var waitForStop = new TaskCompletionSource<object>(TaskCreationOptions.RunContinuationsAsynchronously);
+                applicationLifetime.ApplicationStopping.Register(obj =>
+                {
+                    var tcs = (TaskCompletionSource<object>)obj;
+                    tcs.TrySetResult(null);
+                }, waitForStop);
+
+                await waitForStop.Task;
+
+                // WebHost will use its default ShutdownTimeout if none is specified.
+                await host.StopAsync();
             }
         }
     }

src/Microsoft.AspNetCore.TestHost/TestServer.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Net.Http;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Hosting.Server;
@@ -39,7 +40,7 @@ namespace Microsoft.AspNetCore.TestHost
             Features = featureCollection;
 
             var host = builder.UseServer(this).Build();
-            host.Start();
+            host.StartAsync().GetAwaiter().GetResult();
             _hostInstance = host;
         }
 
@@ -91,7 +92,7 @@ namespace Microsoft.AspNetCore.TestHost
             }
         }
 
-        void IServer.Start<TContext>(IHttpApplication<TContext> application)
+        Task IServer.StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken)
         {
             _application = new ApplicationWrapper<Context>((IHttpApplication<Context>)application, () =>
             {
@@ -100,6 +101,13 @@ namespace Microsoft.AspNetCore.TestHost
                     throw new ObjectDisposedException(GetType().FullName);
                 }
             });
+
+            return Task.CompletedTask;
+        }
+
+        Task IServer.StopAsync(CancellationToken cancellationToken)
+        {
+            return Task.CompletedTask;
         }
 
         private class ApplicationWrapper<TContext> : IHttpApplication<TContext>

test/Microsoft.AspNetCore.Hosting.TestSites/Program.cs

@@ -1,11 +1,12 @@
 // 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 Microsoft.AspNetCore.Hosting;
-using Microsoft.Extensions.Configuration;
 using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.AspNetCore.Http.Features;
+using Microsoft.Extensions.Configuration;
 
 namespace ServerComparison.TestSites
 {
@@ -36,8 +37,14 @@ namespace ServerComparison.TestSites
 
         public IFeatureCollection Features { get; } = new FeatureCollection();
 
-        public void Start<TContext>(IHttpApplication<TContext> application)
+        public Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken)
         {
+            return Task.CompletedTask;
+        }
+
+        public Task StopAsync(CancellationToken cancellationToken)
+        {
+            return Task.CompletedTask;
         }
     }
 }

test/Microsoft.AspNetCore.Hosting.Tests/WebHostBuilderTests.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
@@ -48,7 +49,7 @@ namespace Microsoft.AspNetCore.Hosting
             var host = builder.UseServer(server).UseStartup("MissingStartupAssembly").Build();
             using (host)
             {
-                host.Start();
+                await host.StartAsync();
                 await AssertResponseContains(server.RequestDelegate, "MissingStartupAssembly");
             }
         }
@@ -61,7 +62,7 @@ namespace Microsoft.AspNetCore.Hosting
             var host = builder.UseServer(server).UseStartup<StartupStaticCtorThrows>().Build();
             using (host)
             {
-                host.Start();
+                await host.StartAsync();
                 await AssertResponseContains(server.RequestDelegate, "Exception from static constructor");
             }
         }
@@ -74,7 +75,7 @@ namespace Microsoft.AspNetCore.Hosting
             var host = builder.UseServer(server).UseStartup<StartupCtorThrows>().Build();
             using (host)
             {
-                host.Start();
+                await host.StartAsync();
                 await AssertResponseContains(server.RequestDelegate, "Exception from constructor");
             }
         }
@@ -87,7 +88,7 @@ namespace Microsoft.AspNetCore.Hosting
             var host = builder.UseServer(server).UseStartup<StartupThrowTypeLoadException>().Build();
             using (host)
             {
-                host.Start();
+                await host.StartAsync();
                 await AssertResponseContains(server.RequestDelegate, "Message from the LoaderException</div>");
             }
         }
@@ -100,7 +101,7 @@ namespace Microsoft.AspNetCore.Hosting
             var host = builder.UseServer(server).UseStartup<StartupCtorThrows>().Build();
             using (host)
             {
-                host.Start();
+                await host.StartAsync();
                 var services = host.Services.GetServices<IApplicationLifetime>();
                 Assert.NotNull(services);
                 Assert.NotEmpty(services);
@@ -110,7 +111,7 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void DefaultObjectPoolProvider_IsRegistered()
+        public async Task DefaultObjectPoolProvider_IsRegistered()
         {
             var server = new TestServer();
             var host = CreateWebHostBuilder()
@@ -119,7 +120,7 @@ namespace Microsoft.AspNetCore.Hosting
                 .Build();
             using (host)
             {
-                host.Start();
+                await host.StartAsync();
                 Assert.IsType<DefaultObjectPoolProvider>(host.Services.GetService<ObjectPoolProvider>());
             }
         }
@@ -132,7 +133,7 @@ namespace Microsoft.AspNetCore.Hosting
             var host = builder.UseServer(server).UseStartup<StartupConfigureServicesThrows>().Build();
             using (host)
             {
-                host.Start();
+                await host.StartAsync();
                 await AssertResponseContains(server.RequestDelegate, "Exception from ConfigureServices");
             }
         }
@@ -145,7 +146,7 @@ namespace Microsoft.AspNetCore.Hosting
             var host = builder.UseServer(server).UseStartup<StartupConfigureServicesThrows>().Build();
             using (host)
             {
-                host.Start();
+                await host.StartAsync();
                 await AssertResponseContains(server.RequestDelegate, "Exception from Configure");
             }
         }
@@ -810,7 +811,7 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void Build_DoesNotThrowIfUnloadableAssemblyNameInHostingStartupAssembliesAndCaptureStartupErrorsTrue()
+        public async Task Build_DoesNotThrowIfUnloadableAssemblyNameInHostingStartupAssembliesAndCaptureStartupErrorsTrue()
         {
             var provider = new TestLoggerProvider();
             var builder = CreateWebHostBuilder()
@@ -825,7 +826,7 @@ namespace Microsoft.AspNetCore.Hosting
 
             using (var host = builder.Build())
             {
-                host.Start();
+                await host.StartAsync();
                 var context = provider.Sink.Writes.FirstOrDefault(s => s.EventId.Id == LoggerEventIds.HostingStartupAssemblyException);
                 Assert.NotNull(context);
             }
@@ -879,7 +880,7 @@ namespace Microsoft.AspNetCore.Hosting
 
             }
 
-            public void Start<TContext>(IHttpApplication<TContext> application)
+            public Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken)
             {
                 RequestDelegate = async ctx =>
                 {
@@ -895,6 +896,13 @@ namespace Microsoft.AspNetCore.Hosting
                     }
                     application.DisposeContext(httpContext, null);
                 };
+
+                return Task.CompletedTask;
+            }
+
+            public Task StopAsync(CancellationToken cancellationToken)
+            {
+                return Task.CompletedTask;
             }
         }
 

test/Microsoft.AspNetCore.Hosting.Tests/WebHostTests.cs

@@ -23,40 +23,12 @@ using Xunit;
 
 namespace Microsoft.AspNetCore.Hosting
 {
-    public class WebHostTests : IServer
+    public class WebHostTests
     {
-        private readonly IList<StartInstance> _startInstances = new List<StartInstance>();
-        private IFeatureCollection _featuresSupportedByThisHost = NewFeatureCollection();
-
-        public IFeatureCollection Features
-        {
-            get
-            {
-                var features = new FeatureCollection();
-
-                foreach (var feature in _featuresSupportedByThisHost)
-                {
-                    features[feature.Key] = feature.Value;
-                }
-
-                return features;
-            }
-        }
-
-        static IFeatureCollection NewFeatureCollection()
-        {
-            var stub = new StubFeatures();
-            var features = new FeatureCollection();
-            features.Set<IHttpRequestFeature>(stub);
-            features.Set<IHttpResponseFeature>(stub);
-            features.Set<IServerAddressesFeature>(new ServerAddressesFeature());
-            return features;
-        }
-
         [Fact]
-        public void WebHostThrowsWithNoServer()
+        public async Task WebHostThrowsWithNoServer()
         {
-            var ex = Assert.Throws<InvalidOperationException>(() => CreateBuilder().Build().Start());
+            var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => CreateBuilder().Build().StartAsync());
             Assert.Equal("No service for type 'Microsoft.AspNetCore.Hosting.Server.IServer' has been registered.", ex.Message);
         }
 
@@ -67,11 +39,11 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void NoDefaultAddressesAndDoNotPreferHostingUrlsIfNotConfigured()
+        public async Task NoDefaultAddressesAndDoNotPreferHostingUrlsIfNotConfigured()
         {
-            using (var host = CreateBuilder().UseServer(this).Build())
+            using (var host = CreateBuilder().UseFakeServer().Build())
             {
-                host.Start();
+                await host.StartAsync();
                 var serverAddressesFeature = host.ServerFeatures.Get<IServerAddressesFeature>();
                 Assert.False(serverAddressesFeature.Addresses.Any());
                 Assert.False(serverAddressesFeature.PreferHostingUrls);
@@ -79,7 +51,7 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void UsesLegacyConfigurationForAddressesAndDoNotPreferHostingUrlsIfNotConfigured()
+        public async Task UsesLegacyConfigurationForAddressesAndDoNotPreferHostingUrlsIfNotConfigured()
         {
             var data = new Dictionary<string, string>
             {
@@ -88,9 +60,9 @@ namespace Microsoft.AspNetCore.Hosting
 
             var config = new ConfigurationBuilder().AddInMemoryCollection(data).Build();
 
-            using (var host = CreateBuilder(config).UseServer(this).Build())
+            using (var host = CreateBuilder(config).UseFakeServer().Build())
             {
-                host.Start();
+                await host.StartAsync();
                 var serverAddressFeature = host.ServerFeatures.Get<IServerAddressesFeature>();
                 Assert.Equal("http://localhost:5002", serverAddressFeature.Addresses.First());
                 Assert.False(serverAddressFeature.PreferHostingUrls);
@@ -107,7 +79,7 @@ namespace Microsoft.AspNetCore.Hosting
 
             var config = new ConfigurationBuilder().AddInMemoryCollection(data).Build();
 
-            using (var host = CreateBuilder(config).UseServer(this).Build())
+            using (var host = CreateBuilder(config).UseFakeServer().Build())
             {
                 host.Start();
                 var serverAddressFeature = host.ServerFeatures.Get<IServerAddressesFeature>();
@@ -117,7 +89,7 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void UsesNewConfigurationOverLegacyConfigForAddressesAndDoNotPreferHostingUrlsIfNotConfigured()
+        public async Task UsesNewConfigurationOverLegacyConfigForAddressesAndDoNotPreferHostingUrlsIfNotConfigured()
         {
             var data = new Dictionary<string, string>
             {
@@ -127,9 +99,9 @@ namespace Microsoft.AspNetCore.Hosting
 
             var config = new ConfigurationBuilder().AddInMemoryCollection(data).Build();
 
-            using (var host = CreateBuilder(config).UseServer(this).Build())
+            using (var host = CreateBuilder(config).UseFakeServer().Build())
             {
-                host.Start();
+                await host.StartAsync();
                 var serverAddressFeature = host.ServerFeatures.Get<IServerAddressesFeature>();
                 Assert.Equal("http://localhost:5009", serverAddressFeature.Addresses.First());
                 Assert.False(serverAddressFeature.PreferHostingUrls);
@@ -139,7 +111,7 @@ namespace Microsoft.AspNetCore.Hosting
         [Fact]
         public void DoNotPreferHostingUrlsWhenNoAddressConfigured()
         {
-            using (var host = CreateBuilder().UseServer(this).PreferHostingUrls(true).Build())
+            using (var host = CreateBuilder().UseFakeServer().PreferHostingUrls(true).Build())
             {
                 host.Start();
                 var serverAddressesFeature = host.ServerFeatures.Get<IServerAddressesFeature>();
@@ -149,7 +121,7 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void PreferHostingUrlsWhenAddressIsConfigured()
+        public async Task PreferHostingUrlsWhenAddressIsConfigured()
         {
             var data = new Dictionary<string, string>
             {
@@ -158,9 +130,9 @@ namespace Microsoft.AspNetCore.Hosting
 
             var config = new ConfigurationBuilder().AddInMemoryCollection(data).Build();
 
-            using (var host = CreateBuilder(config).UseServer(this).PreferHostingUrls(true).Build())
+            using (var host = CreateBuilder(config).UseFakeServer().PreferHostingUrls(true).Build())
             {
-                host.Start();
+                await host.StartAsync();
                 Assert.True(host.ServerFeatures.Get<IServerAddressesFeature>().PreferHostingUrls);
             }
         }
@@ -169,17 +141,18 @@ namespace Microsoft.AspNetCore.Hosting
         public void WebHostCanBeStarted()
         {
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .UseStartup("Microsoft.AspNetCore.Hosting.Tests")
                 .Start())
             {
+                var server = (FakeServer)host.Services.GetRequiredService<IServer>();
                 Assert.NotNull(host);
-                Assert.Equal(1, _startInstances.Count);
+                Assert.Equal(1, server.StartInstances.Count);
-                Assert.Equal(0, _startInstances[0].DisposeCalls);
+                Assert.Equal(0, server.StartInstances[0].DisposeCalls);
 
                 host.Dispose();
 
-                Assert.Equal(0, _startInstances[0].DisposeCalls);
+                Assert.Equal(1, server.StartInstances[0].DisposeCalls);
             }
         }
 
@@ -187,28 +160,29 @@ namespace Microsoft.AspNetCore.Hosting
         public void WebHostShutsDownWhenTokenTriggers()
         {
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .UseStartup("Microsoft.AspNetCore.Hosting.Tests")
                 .Build())
             {
                 var lifetime = host.Services.GetRequiredService<IApplicationLifetime>();
+                var server = (FakeServer)host.Services.GetRequiredService<IServer>();
 
                 var cts = new CancellationTokenSource();
 
-                Task.Run(() => host.Run(cts.Token));
+                var runInBackground = host.RunAsync(cts.Token);
 
                 // Wait on the host to be started
                 lifetime.ApplicationStarted.WaitHandle.WaitOne();
 
-                Assert.Equal(1, _startInstances.Count);
+                Assert.Equal(1, server.StartInstances.Count);
-                Assert.Equal(0, _startInstances[0].DisposeCalls);
+                Assert.Equal(0, server.StartInstances[0].DisposeCalls);
 
                 cts.Cancel();
 
                 // Wait on the host to shutdown
                 lifetime.ApplicationStopped.WaitHandle.WaitOne();
 
-                Assert.Equal(0, _startInstances[0].DisposeCalls);
+                Assert.Equal(1, server.StartInstances[0].DisposeCalls);
             }
         }
 
@@ -216,7 +190,7 @@ namespace Microsoft.AspNetCore.Hosting
         public void WebHostApplicationLifetimeEventsOrderedCorrectlyDuringShutdown()
         {
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .UseStartup("Microsoft.AspNetCore.Hosting.Tests")
                 .Build())
             {
@@ -251,9 +225,9 @@ namespace Microsoft.AspNetCore.Hosting
                     applicationStoppedEvent.Set();
                 });
 
-                var runHostAndVerifyApplicationStopped = Task.Run(() =>
+                var runHostAndVerifyApplicationStopped = Task.Run(async () =>
                 {
-                    host.Run();
+                    await host.RunAsync();
                     // Check whether the applicationStoppingEvent has been set
                     applicationStoppedCompletedBeforeRunCompleted = applicationStoppedEvent.IsSet;
                 });
@@ -275,10 +249,10 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void WebHostDisposesServiceProvider()
+        public async Task WebHostDisposesServiceProvider()
         {
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .ConfigureServices(s =>
                 {
                     s.AddTransient<IFakeService, FakeService>();
@@ -287,7 +261,7 @@ namespace Microsoft.AspNetCore.Hosting
                 .UseStartup("Microsoft.AspNetCore.Hosting.Tests")
                 .Build())
             {
-                host.Start();
+                await host.StartAsync();
 
                 var singleton = (FakeService)host.Services.GetService<IFakeSingletonService>();
                 var transient = (FakeService)host.Services.GetService<IFakeService>();
@@ -295,6 +269,11 @@ namespace Microsoft.AspNetCore.Hosting
                 Assert.False(singleton.Disposed);
                 Assert.False(transient.Disposed);
 
+                await host.StopAsync();
+
+                Assert.False(singleton.Disposed);
+                Assert.False(transient.Disposed);
+
                 host.Dispose();
 
                 Assert.True(singleton.Disposed);
@@ -303,26 +282,26 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void WebHostNotifiesApplicationStarted()
+        public async Task WebHostNotifiesApplicationStarted()
         {
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .Build())
             {
                 var applicationLifetime = host.Services.GetService<IApplicationLifetime>();
 
                 Assert.False(applicationLifetime.ApplicationStarted.IsCancellationRequested);
 
-                host.Start();
+                await host.StartAsync();
                 Assert.True(applicationLifetime.ApplicationStarted.IsCancellationRequested);
             }
         }
 
         [Fact]
-        public void WebHostNotifiesAllIApplicationLifetimeCallbacksEvenIfTheyThrow()
+        public async Task WebHostNotifiesAllIApplicationLifetimeCallbacksEvenIfTheyThrow()
         {
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .Build())
             {
                 var applicationLifetime = host.Services.GetService<IApplicationLifetime>();
@@ -331,7 +310,7 @@ namespace Microsoft.AspNetCore.Hosting
                 var stopping = RegisterCallbacksThatThrow(applicationLifetime.ApplicationStopping);
                 var stopped = RegisterCallbacksThatThrow(applicationLifetime.ApplicationStopped);
 
-                host.Start();
+                await host.StartAsync();
                 Assert.True(applicationLifetime.ApplicationStarted.IsCancellationRequested);
                 Assert.True(started.All(s => s));
                 host.Dispose();
@@ -341,13 +320,13 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void WebHostNotifiesAllIApplicationLifetimeEventsCallbacksEvenIfTheyThrow()
+        public async Task WebHostNotifiesAllIApplicationLifetimeEventsCallbacksEvenIfTheyThrow()
         {
             bool[] events1 = null;
             bool[] events2 = null;
 
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .ConfigureServices(services =>
                 {
                     events1 = RegisterCallbacksThatThrow(services);
@@ -355,7 +334,7 @@ namespace Microsoft.AspNetCore.Hosting
                 })
                 .Build())
             {
-                host.Start();
+                await host.StartAsync();
                 Assert.True(events1[0]);
                 Assert.True(events2[0]);
                 host.Dispose();
@@ -365,12 +344,13 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void WebHostStopApplicationDoesNotFireStopOnHostedService()
+        public async Task WebHostStopApplicationDoesNotFireStopOnHostedService()
         {
             var stoppingCalls = 0;
+            var disposingCalls = 0;
 
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .ConfigureServices(services =>
                 {
                     Action started = () =>
@@ -382,24 +362,32 @@ namespace Microsoft.AspNetCore.Hosting
                         stoppingCalls++;
                     };
 
-                    services.AddSingleton<IHostedService>(new DelegateHostedService(started, stopping));
+                    Action disposing = () =>
+                    {
+                        disposingCalls++;
+                    };
+
+                    services.AddSingleton<IHostedService>(_ => new DelegateHostedService(started, stopping, disposing));
                 })
                 .Build())
             {
                 var lifetime = host.Services.GetRequiredService<IApplicationLifetime>();
                 lifetime.StopApplication();
 
-                host.Start();
+                await host.StartAsync();
 
                 Assert.Equal(0, stoppingCalls);
+                Assert.Equal(0, disposingCalls);
             }
+            Assert.Equal(1, stoppingCalls);
+            Assert.Equal(1, disposingCalls);
         }
 
         [Fact]
-        public void HostedServiceCanInjectApplicationLifetime()
+        public async Task HostedServiceCanInjectApplicationLifetime()
         {
             using (var host = CreateBuilder()
-                   .UseServer(this)
+                   .UseFakeServer()
                    .ConfigureServices(services =>
                    {
                        services.AddSingleton<IHostedService, TestHostedService>();
@@ -409,19 +397,21 @@ namespace Microsoft.AspNetCore.Hosting
                 var lifetime = host.Services.GetRequiredService<IApplicationLifetime>();
                 lifetime.StopApplication();
 
-                host.Start();
+                await host.StartAsync();
                 var svc = (TestHostedService)host.Services.GetRequiredService<IHostedService>();
                 Assert.True(svc.StartCalled);
-                host.Dispose();
+
+                await host.StopAsync();
                 Assert.True(svc.StopCalled);
+                host.Dispose();
             }
         }
 
         [Fact]
-        public void HostedServiceStartNotCalledIfWebHostNotStarted()
+        public async Task HostedServiceStartNotCalledIfWebHostNotStarted()
         {
             using (var host = CreateBuilder()
-                   .UseServer(this)
+                   .UseFakeServer()
                    .ConfigureServices(services =>
                    {
                        services.AddSingleton<IHostedService, TestHostedService>();
@@ -433,19 +423,23 @@ namespace Microsoft.AspNetCore.Hosting
 
                 var svc = (TestHostedService)host.Services.GetRequiredService<IHostedService>();
                 Assert.False(svc.StartCalled);
+                await host.StopAsync();
+                Assert.False(svc.StopCalled);
                 host.Dispose();
                 Assert.False(svc.StopCalled);
+                Assert.True(svc.DisposeCalled);
             }
         }
 
         [Fact]
-        public void WebHostDisposeApplicationFiresStopOnHostedService()
+        public async Task WebHostStopApplicationFiresStopOnHostedService()
         {
             var stoppingCalls = 0;
             var startedCalls = 0;
+            var disposingCalls = 0;
 
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .ConfigureServices(services =>
                 {
                     Action started = () =>
@@ -458,28 +452,90 @@ namespace Microsoft.AspNetCore.Hosting
                         stoppingCalls++;
                     };
 
-                    services.AddSingleton<IHostedService>(new DelegateHostedService(started, stopping));
+                    Action disposing = () =>
+                    {
+                        disposingCalls++;
+                    };
+
+                    services.AddSingleton<IHostedService>(_ => new DelegateHostedService(started, stopping, disposing));
                 })
                 .Build())
             {
                 var lifetime = host.Services.GetRequiredService<IApplicationLifetime>();
 
-                host.Start();
+                Assert.Equal(0, startedCalls);
+
+                await host.StartAsync();
+                Assert.Equal(1, startedCalls);
+                Assert.Equal(0, stoppingCalls);
+                Assert.Equal(0, disposingCalls);
+
+                await host.StopAsync();
+
+                Assert.Equal(1, startedCalls);
+                Assert.Equal(1, stoppingCalls);
+                Assert.Equal(0, disposingCalls);
+
                 host.Dispose();
 
                 Assert.Equal(1, startedCalls);
                 Assert.Equal(1, stoppingCalls);
+                Assert.Equal(1, disposingCalls);
             }
         }
 
         [Fact]
-        public void WebHostNotifiesAllIHostedServicesAndIApplicationLifetimeCallbacksEvenIfTheyThrow()
+        public async Task WebHostDisposeApplicationFiresStopOnHostedService()
+        {
+            var stoppingCalls = 0;
+            var startedCalls = 0;
+            var disposingCalls = 0;
+
+            using (var host = CreateBuilder()
+                .UseFakeServer()
+                .ConfigureServices(services =>
+                {
+                    Action started = () =>
+                    {
+                        startedCalls++;
+                    };
+
+                    Action stopping = () =>
+                    {
+                        stoppingCalls++;
+                    };
+
+                    Action disposing = () =>
+                    {
+                        disposingCalls++;
+                    };
+
+                    services.AddSingleton<IHostedService>(_ => new DelegateHostedService(started, stopping, disposing));
+                })
+                .Build())
+            {
+                var lifetime = host.Services.GetRequiredService<IApplicationLifetime>();
+
+                Assert.Equal(0, startedCalls);
+                await host.StartAsync();
+                Assert.Equal(1, startedCalls);
+                Assert.Equal(0, stoppingCalls);
+                Assert.Equal(0, disposingCalls);
+                host.Dispose();
+
+                Assert.Equal(1, stoppingCalls);
+                Assert.Equal(1, disposingCalls);
+            }
+        }
+
+        [Fact]
+        public async Task WebHostNotifiesAllIHostedServicesAndIApplicationLifetimeCallbacksEvenIfTheyThrow()
         {
             bool[] events1 = null;
             bool[] events2 = null;
 
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .ConfigureServices(services =>
                 {
                     events1 = RegisterCallbacksThatThrow(services);
@@ -492,7 +548,7 @@ namespace Microsoft.AspNetCore.Hosting
                 var started = RegisterCallbacksThatThrow(applicationLifetime.ApplicationStarted);
                 var stopping = RegisterCallbacksThatThrow(applicationLifetime.ApplicationStopping);
 
-                host.Start();
+                await host.StartAsync();
                 Assert.True(events1[0]);
                 Assert.True(events2[0]);
                 Assert.True(started.All(s => s));
@@ -504,15 +560,15 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void WebHostInjectsHostingEnvironment()
+        public async Task WebHostInjectsHostingEnvironment()
         {
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .UseStartup("Microsoft.AspNetCore.Hosting.Tests")
                 .UseEnvironment("WithHostingEnvironment")
                 .Build())
             {
-                host.Start();
+                await host.StartAsync();
                 var env = host.Services.GetService<IHostingEnvironment>();
                 Assert.Equal("Changed", env.EnvironmentName);
             }
@@ -526,7 +582,7 @@ namespace Microsoft.AspNetCore.Hosting
                 {
                     services.AddTransient<IStartup, TestStartup>();
                 })
-                .UseServer(this)
+                .UseFakeServer()
                 .UseStartup("Microsoft.AspNetCore.Hosting.Tests");
 
             Assert.Throws<NotImplementedException>(() => builder.Build());
@@ -535,7 +591,7 @@ namespace Microsoft.AspNetCore.Hosting
         [Fact]
         public void CanCreateApplicationServicesWithAddedServices()
         {
-            using (var host = CreateBuilder().UseServer(this).ConfigureServices(services => services.AddOptions()).Build())
+            using (var host = CreateBuilder().UseFakeServer().ConfigureServices(services => services.AddOptions()).Build())
             {
                 Assert.NotNull(host.Services.GetRequiredService<IOptions<object>>());
             }
@@ -547,7 +603,7 @@ namespace Microsoft.AspNetCore.Hosting
             // Verify ordering
             var configureOrder = 0;
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .ConfigureServices(services =>
                 {
                     services.AddTransient<IStartupFilter>(serviceProvider => new TestFilter(
@@ -593,7 +649,7 @@ namespace Microsoft.AspNetCore.Hosting
         [Fact]
         public void EnvDefaultsToProductionIfNoConfig()
         {
-            using (var host = CreateBuilder().UseServer(this).Build())
+            using (var host = CreateBuilder().UseFakeServer().Build())
             {
                 var env = host.Services.GetService<IHostingEnvironment>();
                 Assert.Equal(EnvironmentName.Production, env.EnvironmentName);
@@ -612,7 +668,7 @@ namespace Microsoft.AspNetCore.Hosting
                 .AddInMemoryCollection(vals);
             var config = builder.Build();
 
-            using (var host = CreateBuilder(config).UseServer(this).Build())
+            using (var host = CreateBuilder(config).UseFakeServer().Build())
             {
                 var env = host.Services.GetService<IHostingEnvironment>();
                 Assert.Equal("Staging", env.EnvironmentName);
@@ -631,7 +687,7 @@ namespace Microsoft.AspNetCore.Hosting
                 .AddInMemoryCollection(vals);
             var config = builder.Build();
 
-            using (var host = CreateBuilder(config).UseServer(this).Build())
+            using (var host = CreateBuilder(config).UseFakeServer().Build())
             {
                 var env = host.Services.GetService<IHostingEnvironment>();
                 Assert.Equal(Path.GetFullPath("testroot"), env.WebRootPath);
@@ -640,11 +696,11 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void IsEnvironment_Extension_Is_Case_Insensitive()
+        public async Task IsEnvironment_Extension_Is_Case_Insensitive()
         {
-            using (var host = CreateBuilder().UseServer(this).Build())
+            using (var host = CreateBuilder().UseFakeServer().Build())
             {
-                host.Start();
+                await host.StartAsync();
                 var env = host.Services.GetRequiredService<IHostingEnvironment>();
                 Assert.True(env.IsEnvironment(EnvironmentName.Production));
                 Assert.True(env.IsEnvironment("producTion"));
@@ -652,7 +708,7 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void WebHost_CreatesDefaultRequestIdentifierFeature_IfNotPresent()
+        public async Task WebHost_CreatesDefaultRequestIdentifierFeature_IfNotPresent()
         {
             // Arrange
             HttpContext httpContext = null;
@@ -665,7 +721,7 @@ namespace Microsoft.AspNetCore.Hosting
             using (var host = CreateHost(requestDelegate))
             {
                 // Act
-                host.Start();
+                await host.StartAsync();
 
                 // Assert
                 Assert.NotNull(httpContext);
@@ -676,7 +732,7 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void WebHost_DoesNot_CreateDefaultRequestIdentifierFeature_IfPresent()
+        public async Task WebHost_DoesNot_CreateDefaultRequestIdentifierFeature_IfPresent()
         {
             // Arrange
             HttpContext httpContext = null;
@@ -686,12 +742,18 @@ namespace Microsoft.AspNetCore.Hosting
                 return Task.FromResult(0);
             });
             var requestIdentifierFeature = new StubHttpRequestIdentifierFeature();
-            _featuresSupportedByThisHost[typeof(IHttpRequestIdentifierFeature)] = requestIdentifierFeature;
 
             using (var host = CreateHost(requestDelegate))
             {
+                var server = (FakeServer)host.Services.GetRequiredService<IServer>();
+                server.CreateRequestFeatures = () =>
+                {
+                    var features = FakeServer.NewFeatureCollection();
+                    features.Set<IHttpRequestIdentifierFeature>(requestIdentifierFeature);
+                    return features;
+                };
                 // Act
-                host.Start();
+                await host.StartAsync();
 
                 // Assert
                 Assert.NotNull(httpContext);
@@ -700,14 +762,14 @@ namespace Microsoft.AspNetCore.Hosting
         }
 
         [Fact]
-        public void WebHost_InvokesConfigureMethodsOnlyOnce()
+        public async Task WebHost_InvokesConfigureMethodsOnlyOnce()
         {
             using (var host = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .UseStartup<CountStartup>()
                 .Build())
             {
-                host.Start();
+                await host.StartAsync();
                 var services = host.Services;
                 var services2 = host.Services;
                 Assert.Equal(1, CountStartup.ConfigureCount);
@@ -735,7 +797,7 @@ namespace Microsoft.AspNetCore.Hosting
         public void WebHost_ThrowsForBadConfigureServiceSignature()
         {
             var builder = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .UseStartup<BadConfigureServicesStartup>();
 
             var ex = Assert.Throws<InvalidOperationException>(() => builder.Build());
@@ -751,7 +813,7 @@ namespace Microsoft.AspNetCore.Hosting
         private IWebHost CreateHost(RequestDelegate requestDelegate)
         {
             var builder = CreateBuilder()
-                .UseServer(this)
+                .UseFakeServer()
                 .Configure(
                     appBuilder =>
                     {
@@ -782,7 +844,7 @@ namespace Microsoft.AspNetCore.Hosting
                 throw new InvalidOperationException();
             };
 
-            services.AddSingleton<IHostedService>(new DelegateHostedService(started, stopping));
+            services.AddSingleton<IHostedService>(new DelegateHostedService(started, stopping, () => { }));
 
             return events;
         }
@@ -802,35 +864,7 @@ namespace Microsoft.AspNetCore.Hosting
             return signals;
         }
 
-        public void Start<TContext>(IHttpApplication<TContext> application)
+        private class TestHostedService : IHostedService, IDisposable
-        {
-            var startInstance = new StartInstance();
-            _startInstances.Add(startInstance);
-            var context = application.CreateContext(Features);
-            try
-            {
-                application.ProcessRequestAsync(context);
-            }
-            catch (Exception ex)
-            {
-                application.DisposeContext(context, ex);
-                throw;
-            }
-            application.DisposeContext(context, null);
-        }
-
-        public void Dispose()
-        {
-            if (_startInstances != null)
-            {
-                foreach (var startInstance in _startInstances)
-                {
-                    startInstance.Dispose();
-                }
-            }
-        }
-
-        private class TestHostedService : IHostedService
         {
             private readonly IApplicationLifetime _lifetime;
 
@@ -841,6 +875,7 @@ namespace Microsoft.AspNetCore.Hosting
 
             public bool StartCalled { get; set; }
             public bool StopCalled { get; set; }
+            public bool DisposeCalled { get; set; }
 
             public void Start()
             {
@@ -851,34 +886,117 @@ namespace Microsoft.AspNetCore.Hosting
             {
                 StopCalled = true;
             }
+
+            public void Dispose()
+            {
+                DisposeCalled = true;
+            }
         }
 
-        private class DelegateHostedService : IHostedService
+        private class DelegateHostedService : IHostedService, IDisposable
         {
             private readonly Action _started;
             private readonly Action _stopping;
+            private readonly Action _disposing;
 
-            public DelegateHostedService(Action started, Action stopping)
+            public DelegateHostedService(Action started, Action stopping, Action disposing)
             {
                 _started = started;
                 _stopping = stopping;
+                _disposing = disposing;
             }
 
             public void Start() => _started();
 
             public void Stop() => _stopping();
+
+            public void Dispose() => _disposing();
         }
 
-        private class StartInstance : IDisposable
+        public class StartInstance : IDisposable
         {
+            public int StopCalls { get; set; }
+
             public int DisposeCalls { get; set; }
 
+            public void Stop()
+            {
+                StopCalls += 1;
+            }
+
             public void Dispose()
             {
                 DisposeCalls += 1;
             }
         }
 
+        public class FakeServer : IServer
+        {
+            public FakeServer()
+            {
+                Features = new FeatureCollection();
+                Features.Set<IServerAddressesFeature>(new ServerAddressesFeature());
+            }
+
+            public IList<StartInstance> StartInstances { get; } = new List<StartInstance>();
+
+            public Func<IFeatureCollection> CreateRequestFeatures { get; set; } = NewFeatureCollection;
+
+            public IFeatureCollection Features { get; }
+
+            public static IFeatureCollection NewFeatureCollection()
+            {
+                var stub = new StubFeatures();
+                var features = new FeatureCollection();
+                features.Set<IHttpRequestFeature>(stub);
+                features.Set<IHttpResponseFeature>(stub);
+                return features;
+            }
+
+            public Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken)
+            {
+                var startInstance = new StartInstance();
+                StartInstances.Add(startInstance);
+                var context = application.CreateContext(CreateRequestFeatures());
+                try
+                {
+                    application.ProcessRequestAsync(context);
+                }
+                catch (Exception ex)
+                {
+                    application.DisposeContext(context, ex);
+                    throw;
+                }
+                application.DisposeContext(context, null);
+
+                return Task.CompletedTask;
+            }
+
+            public Task StopAsync(CancellationToken cancellationToken)
+            {
+                if (StartInstances != null)
+                {
+                    foreach (var startInstance in StartInstances)
+                    {
+                        startInstance.Stop();
+                    }
+                }
+
+                return Task.CompletedTask;
+            }
+
+            public void Dispose()
+            {
+                if (StartInstances != null)
+                {
+                    foreach (var startInstance in StartInstances)
+                    {
+                        startInstance.Dispose();
+                    }
+                }
+            }
+        }
+
         private class TestStartup : IStartup
         {
             public void Configure(IApplicationBuilder app)
@@ -1040,4 +1158,12 @@ namespace Microsoft.AspNetCore.Hosting
             public string TraceIdentifier { get; set; }
         }
     }
+
+    public static class TestServerWebHostExtensions
+    {
+        public static IWebHostBuilder UseFakeServer(this IWebHostBuilder builder)
+        {
+            return builder.ConfigureServices(services => services.AddSingleton<IServer, WebHostTests.FakeServer>());
+        }
+    }
 }