Added ApplicationSchedulingMode to KestrelServerOptions (#1759)

* Added ApplicationSchedulingMode to KestrelServerOptions
- Made default mode Default instead of ThreadPool

samples/SampleApp/Startup.cs

@@ -8,7 +8,7 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
-using Microsoft.AspNetCore.Server.Kestrel.Core.Internal;
+using Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions;
 using Microsoft.Extensions.Logging;
 
 namespace SampleApp
@@ -45,7 +45,7 @@ namespace SampleApp
                 .UseKestrel(options =>
                 {
                     // Run callbacks on the transport thread
-                    options.UseTransportThread = true;
+                    options.ApplicationSchedulingMode = SchedulingMode.Inline;
 
                     options.Listen(IPAddress.Loopback, 5000, listenOptions =>
                     {

src/Microsoft.AspNetCore.Server.Kestrel.Core/KestrelServer.cs

@@ -72,14 +72,20 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core
             var systemClock = new SystemClock();
             var dateHeaderValueManager = new DateHeaderValueManager(systemClock);
 
-            IThreadPool threadPool;
-            if (serverOptions.UseTransportThread)
+            // TODO: This logic will eventually move into the IConnectionHandler<T> and off
+            // the service context once we get to https://github.com/aspnet/KestrelHttpServer/issues/1662
+            IThreadPool threadPool = null;
+            switch (serverOptions.ApplicationSchedulingMode)
             {
-                threadPool = new InlineLoggingThreadPool(trace);
-            }
-            else
-            {
-                threadPool = new LoggingThreadPool(trace);
+                case SchedulingMode.Default:
+                case SchedulingMode.ThreadPool:
+                    threadPool = new LoggingThreadPool(trace);
+                    break;
+                case SchedulingMode.Inline:
+                    threadPool = new InlineLoggingThreadPool(trace);
+                    break;
+                default:
+                    throw new NotSupportedException($"Unknown transport mode {serverOptions.ApplicationSchedulingMode}");
             }
 
             return new ServiceContext

src/Microsoft.AspNetCore.Server.Kestrel.Core/KestrelServerOptions.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Net;
+using Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core
 {
@@ -33,6 +34,12 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core
         /// </summary>
         public bool UseTransportThread { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value that determines how Kestrel should schedule user callbacks.
+        /// </summary>
+        /// <remarks>The default mode is <see cref="SchedulingMode.Default"/></remarks>
+        public SchedulingMode ApplicationSchedulingMode { get; set; } = SchedulingMode.Default;
+
         /// <summary>
         /// Enables the Listen options callback to resolve and use services registered by the application during startup.
         /// Typically initialized by UseKestrel()"/>.

src/Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions/SchedulingMode.cs

@@ -0,0 +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.
+
+namespace Microsoft.AspNetCore.Server.Kestrel.Transport.Abstractions
+{
+    public enum SchedulingMode
+    {
+        Default,
+        ThreadPool,
+        Inline
+    }
+}