Add ObjectPool<StringBuilder> to default services

- can now use pooled `StringBuilder`s to address aspnet/HttpAbstractions#561 and similar issues

nit: Fix incomplete test noted when adding new one

Author: dougbu

src/Microsoft.AspNetCore.Hosting/WebHostBuilder.cs

@@ -6,6 +6,7 @@
 using System.Diagnostics;
 using System.IO;
 using System.Reflection;
+using System.Text;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting.Builder;
 using Microsoft.AspNetCore.Hosting.Internal;
@@ -17,6 +18,7 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.ObjectPool;
 using Microsoft.Extensions.PlatformAbstractions;
 
 namespace Microsoft.AspNetCore.Hosting
@@ -26,6 +28,11 @@ namespace Microsoft.AspNetCore.Hosting
     /// </summary>
     public class WebHostBuilder : IWebHostBuilder
     {
+        // StringBuilderPooledObjectPolicy.MaximumRetainedCapacity's default is too small for general use and will
+        // cause useful StringBuilders to be thrown away in common scenarios e.g. serializing an antiforgery cookie.
+        // Instead of that value (4 kB), allow the few StringBuilders to grow to 1 MB.
+        private const int MaximumBuilderSize = 0x100000;
+
         private readonly IHostingEnvironment _hostingEnvironment;
         private readonly ILoggerFactory _loggerFactory;
         private readonly List<Action<IServiceCollection>> _configureServicesDelegates;
@@ -135,7 +142,7 @@ public IWebHostBuilder Configure(Action<IApplicationBuilder> configureApp)
         }
 
         /// <summary>
-        /// Configure the provided <see cref="ILoggerFactory"/> which will be available as a hosting service. 
+        /// Configure the provided <see cref="ILoggerFactory"/> which will be available as a hosting service.
         /// </summary>
         /// <param name="configureLogging">The delegate that configures the <see cref="ILoggerFactory"/>.</param>
         /// <returns>The <see cref="IWebHostBuilder"/>.</returns>
@@ -155,7 +162,7 @@ public IWebHost Build()
 
             var appEnvironment = hostingContainer.GetRequiredService<IApplicationEnvironment>();
             var startupLoader = hostingContainer.GetRequiredService<IStartupLoader>();
-            
+
             var contentRootPath = ResolveContentRootPath(_options.ContentRootPath, appEnvironment.ApplicationBasePath);
             var applicationName = ResolveApplicationName() ?? appEnvironment.ApplicationName;
 
@@ -198,6 +205,17 @@ private IServiceCollection BuildHostingServices()
             services.AddSingleton<DiagnosticSource>(diagnosticSource);
             services.AddSingleton<DiagnosticListener>(diagnosticSource);
 
+            services.AddSingleton<ObjectPool<StringBuilder>>(serviceProvider =>
+            {
+                var provider = new DefaultObjectPoolProvider();
+                var policy = new StringBuilderPooledObjectPolicy
+                {
+                    MaximumRetainedCapacity = MaximumBuilderSize,
+                };
+
+                return provider.Create(policy);
+            });
+
             // Conjure up a RequestServices
             services.AddTransient<IStartupFilter, AutoRequestServicesStartupFilter>();
 

src/Microsoft.AspNetCore.Hosting/project.json

@@ -18,14 +18,15 @@
     "Microsoft.AspNetCore.Hosting.Server.Abstractions": "1.0.0-*",
     "Microsoft.AspNetCore.Http": "1.0.0-*",
     "Microsoft.AspNetCore.Http.Extensions": "1.0.0-*",
-    "Microsoft.Extensions.FileProviders.Physical": "1.0.0-*",
-    "Microsoft.Extensions.Options": "1.0.0-*",
     "Microsoft.Extensions.Configuration": "1.0.0-*",
     "Microsoft.Extensions.Configuration.CommandLine": "1.0.0-*",
     "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0-*",
     "Microsoft.Extensions.Configuration.Json": "1.0.0-*",
     "Microsoft.Extensions.DependencyInjection": "1.0.0-*",
+    "Microsoft.Extensions.FileProviders.Physical": "1.0.0-*",
     "Microsoft.Extensions.Logging": "1.0.0-*",
+    "Microsoft.Extensions.ObjectPool": "1.0.0-*",
+    "Microsoft.Extensions.Options": "1.0.0-*",
     "Microsoft.Extensions.PlatformAbstractions": "1.0.0-*",
     "Microsoft.Extensions.TypeNameHelper.Sources": {
       "version": "1.0.0-*",

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

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting.Fakes;
 using Microsoft.AspNetCore.Hosting.Internal;
@@ -13,8 +14,8 @@
 using Microsoft.AspNetCore.Http.Internal;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.ObjectPool;
 using Microsoft.Extensions.PlatformAbstractions;
-using System.Reflection;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Hosting
@@ -92,8 +93,27 @@ public async Task IApplicationLifetimeRegisteredEvenWhenStartupCtorThrows_Fallba
             using (host)
             {
                 host.Start();
-                var service = host.Services.GetServices<IApplicationLifetime>();
-                Assert.NotNull(service);
+                var services = host.Services.GetServices<IApplicationLifetime>();
+                Assert.NotNull(services);
+                Assert.NotEmpty(services);
+
+                await AssertResponseContains(server.RequestDelegate, "Exception from constructor");
+            }
+        }
+
+        [Fact]
+        public async Task ObjectPoolOfStringBuilderRegistered_EvenWhenStartupCtorThrows()
+        {
+            var builder = CreateWebHostBuilder();
+            var server = new TestServer();
+            var host = builder.UseServer(server).UseStartup<StartupCtorThrows>().Build();
+            using (host)
+            {
+                host.Start();
+                var services = host.Services.GetServices<ObjectPool<StringBuilder>>();
+                Assert.NotNull(services);
+                Assert.NotEmpty(services);
+
                 await AssertResponseContains(server.RequestDelegate, "Exception from constructor");
             }
         }