Tear down pending HTTP connection when the originating request completes

src/libraries/Common/src/System/Threading/Tasks/TaskCompletionSourceWithCancellation.cs

@@ -8,7 +8,7 @@ namespace System.Threading.Tasks
     /// <seealso cref="OperationCanceledException"/>s contain the relevant <see cref="CancellationToken"/>,
     /// while also avoiding unnecessary allocations for closure captures.
     /// </summary>
-    internal sealed class TaskCompletionSourceWithCancellation<T> : TaskCompletionSource<T>
+    internal class TaskCompletionSourceWithCancellation<T> : TaskCompletionSource<T>
     {
         public TaskCompletionSourceWithCancellation() : base(TaskCreationOptions.RunContinuationsAsynchronously)
         {

src/libraries/Common/tests/System/Net/Http/GenericLoopbackServer.cs

@@ -152,6 +152,9 @@ public abstract class GenericLoopbackConnection : IAsyncDisposable
         /// <summary>Waits for the client to signal cancellation.</summary>
         public abstract Task WaitForCloseAsync(CancellationToken cancellationToken);
 
+        /// <summary>Reset the connection's internal state so it can process further requests.</summary>
+        public virtual void CompleteRequestProcessing() { }
+
         /// <summary>Helper function to make it easier to convert old test with strings.</summary>
         public async Task SendResponseBodyAsync(string content, bool isFinal = true)
         {

src/libraries/Common/tests/System/Net/Http/LoopbackServer.cs

@@ -873,7 +873,7 @@ public override async Task<Byte[]> ReadRequestBodyAsync()
                 return buffer;
             }
 
-            public void CompleteRequestProcessing()
+            public override void CompleteRequestProcessing()
             {
                 _contentLength = 0;
                 _bodyRead = false;

src/libraries/System.Net.Http/src/System.Net.Http.csproj

@@ -138,8 +138,6 @@
              Link="Common\System\Net\HttpDateParser.cs" />
     <Compile Include="$(CommonPath)System\Text\SimpleRegex.cs"
              Link="Common\System\Text\SimpleRegex.cs" />
-    <Compile Include="$(CommonPath)System\Threading\Tasks\TaskCompletionSourceWithCancellation.cs"
-             Link="Common\System\Threading\Tasks\TaskCompletionSourceWithCancellation.cs" />
     <Compile Include="$(CommonPath)System\HexConverter.cs"
              Link="Common\System\HexConverter.cs" />
     <Compile Include="$(CommonPath)System\Net\ArrayBuffer.cs"
@@ -226,6 +224,8 @@
              Link="Common\System\Net\DebugSafeHandle.cs" />
     <Compile Include="$(CommonPath)System\Net\DebugSafeHandleZeroOrMinusOneIsInvalid.cs"
              Link="Common\System\Net\DebugSafeHandleZeroOrMinusOneIsInvalid.cs" />
+    <Compile Include="$(CommonPath)System\Threading\Tasks\TaskCompletionSourceWithCancellation.cs"
+             Link="Common\System\Threading\Tasks\TaskCompletionSourceWithCancellation.cs" />
   <!-- Header support -->
     <Compile Include="$(CommonPath)System\Net\Http\aspnetcore\IHttpStreamHeadersHandler.cs">
       <Link>Common\System\Net\Http\aspnetcore\IHttpStreamHeadersHandler.cs</Link>

src/libraries/System.Net.Http/src/System/Net/Http/GlobalHttpSettings.cs

@@ -45,6 +45,10 @@ internal static class SocketsHttpHandler
             // Defaults to 1.0. Higher values result in shorter window, but slower downloads.
             public static double Http2StreamWindowScaleThresholdMultiplier { get; } = GetHttp2StreamWindowScaleThresholdMultiplier();
 
+            public static int PendingConnectionTimeoutOnRequestCompletion { get; } = RuntimeSettingParser.QueryRuntimeSettingInt32(
+                "System.Net.SocketsHttpHandler.PendingConnectionTimeoutOnRequestCompletion",
+                "DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_PENDINGCONNECTIONTIMEOUTONREQUESTCOMPLETION", 5000);
+
             public const int DefaultHttp2MaxStreamWindowSize = 16 * 1024 * 1024;
             public const double DefaultHttp2StreamWindowScaleThresholdMultiplier = 1.0;
 

src/libraries/System.Net.Http/tests/FunctionalTests/HttpClientTest.cs

@@ -821,7 +821,7 @@ public async Task ConnectTimeout_NotWrappedInMultipleTimeoutExceptions()
             Assert.Contains("ConnectTimeout", connectTimeoutException.Message);
 
             Assert.Null(connectTimeoutException.InnerException);
-            Assert.DoesNotContain("42", e.ToString());
+            Assert.DoesNotContain("HttpClient.Timeout", e.ToString());
         }
 
         [Fact]

src/libraries/System.Net.Http/tests/FunctionalTests/SocketsHttpHandlerTest.Cancellation.NonParallel.cs

@@ -0,0 +1,140 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.IO;
+using System.Net.Sockets;
+using System.Net.Test.Common;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.DotNet.RemoteExecutor;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace System.Net.Http.Functional.Tests
+{
+    [Collection(nameof(DisableParallelization))] // Reduces chance of timing-related issues
+    [ConditionalClass(typeof(SocketsHttpHandler), nameof(SocketsHttpHandler.IsSupported))]
+    public class SocketsHttpHandler_Cancellation_Test_NonParallel : HttpClientHandlerTestBase
+    {
+        public SocketsHttpHandler_Cancellation_Test_NonParallel(ITestOutputHelper output) : base(output)
+        {
+        }
+
+        [OuterLoop("Incurs significant delay.")]
+        [ConditionalTheory(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        [InlineData("1.1", 10_000, 1_000, 100)]
+        [InlineData("2.0", 10_000, 1_000, 100)]
+        [InlineData("1.1", 20_000, 10_000, null)]
+        [InlineData("2.0", 20_000, 10_000, null)]
+        public static void CancelPendingRequest_DropsStalledConnectionAttempt(string versionString, int firstConnectionDelayMs, int requestTimeoutMs, int? pendingConnectionTimeoutOnRequestCompletion)
+        {
+            RemoteInvokeOptions options = new RemoteInvokeOptions();
+            if (pendingConnectionTimeoutOnRequestCompletion is not null)
+            {
+                options.StartInfo.EnvironmentVariables["DOTNET_SYSTEM_NET_HTTP_SOCKETSHTTPHANDLER_PENDINGCONNECTIONTIMEOUTONREQUESTCOMPLETION"] = pendingConnectionTimeoutOnRequestCompletion.ToString();
+            }
+
+            RemoteExecutor.Invoke(CancelPendingRequest_DropsStalledConnectionAttempt_Impl, versionString, firstConnectionDelayMs.ToString(), requestTimeoutMs.ToString(), options).Dispose();
+        }
+
+        private static async Task CancelPendingRequest_DropsStalledConnectionAttempt_Impl(string versionString, string firstConnectionDelayMsString, string requestTimeoutMsString)
+        {
+            var version = Version.Parse(versionString);
+            LoopbackServerFactory factory = GetFactoryForVersion(version);
+
+            const int AttemptCount = 3;
+            int firstConnectionDelayMs = int.Parse(firstConnectionDelayMsString);
+            int requestTimeoutMs = int.Parse(requestTimeoutMsString);
+            bool firstConnection = true;
+
+            using CancellationTokenSource cts0 = new CancellationTokenSource(requestTimeoutMs);
+
+            await factory.CreateClientAndServerAsync(async uri =>
+            {
+                using var handler = CreateHttpClientHandler(version);
+                GetUnderlyingSocketsHttpHandler(handler).ConnectCallback = DoConnect;
+                using var client = new HttpClient(handler) { DefaultRequestVersion = version };
+
+                await Assert.ThrowsAnyAsync<TaskCanceledException>(async () =>
+                {
+                    await client.GetAsync(uri, cts0.Token);
+                });
+
+                for (int i = 0; i < AttemptCount; i++)
+                {
+                    using var cts1 = new CancellationTokenSource(requestTimeoutMs);
+                    using var response = await client.GetAsync(uri, cts1.Token);
+                    Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+                }
+            }, async server =>
+            {
+                await server.AcceptConnectionAsync(async connection =>
+                {
+                    for (int i = 0; i < AttemptCount; i++)
+                    {
+                        await connection.ReadRequestDataAsync();
+                        await connection.SendResponseAsync();
+                        connection.CompleteRequestProcessing();
+                    }
+                });
+            });
+
+            async ValueTask<Stream> DoConnect(SocketsHttpConnectionContext ctx, CancellationToken cancellationToken)
+            {
+                if (firstConnection)
+                {
+                    firstConnection = false;
+                    await Task.Delay(100, cancellationToken); // Wait for the request to be pushed to the queue
+                    cts0.Cancel(); // cancel the first request faster than RequestTimeoutMs
+                    await Task.Delay(firstConnectionDelayMs, cancellationToken); // Simulate stalled connection
+                }
+                var s = new Socket(SocketType.Stream, ProtocolType.Tcp) { NoDelay = true };
+                await s.ConnectAsync(ctx.DnsEndPoint, cancellationToken);
+
+                return new NetworkStream(s, ownsSocket: true);
+            }
+        }
+
+        [OuterLoop("Incurs significant delay.")]
+        [ConditionalTheory(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        [InlineData(20_000)]
+        [InlineData(Timeout.Infinite)]
+        public void PendingConnectionTimeout_HighValue_PendingConnectionIsNotCancelled(int timeout)
+        {
+            RemoteExecutor.Invoke(async timoutStr =>
+            {
+                // Setup "infinite" timeout of int.MaxValue milliseconds
+                AppContext.SetData("System.Net.SocketsHttpHandler.PendingConnectionTimeoutOnRequestCompletion", int.Parse(timoutStr));
+
+                bool connected = false;
+                CancellationTokenSource cts = new CancellationTokenSource();
+
+                await new Http11LoopbackServerFactory().CreateClientAndServerAsync(async uri =>
+                {
+                    using var handler = CreateHttpClientHandler(HttpVersion.Version11);
+                    GetUnderlyingSocketsHttpHandler(handler).ConnectCallback = DoConnect;
+                    using var client = new HttpClient(handler) { DefaultRequestVersion = HttpVersion.Version11 };
+
+                    await Assert.ThrowsAnyAsync<TaskCanceledException>(() => client.GetAsync(uri, cts.Token));
+                },
+                async server => {
+                    await server.AcceptConnectionAsync(_ => Task.CompletedTask).WaitAsync(30_000);
+                });
+
+                async ValueTask<Stream> DoConnect(SocketsHttpConnectionContext ctx, CancellationToken cancellationToken)
+                {
+                    var s = new Socket(SocketType.Stream, ProtocolType.Tcp) { NoDelay = true };
+                    await Task.Delay(100, cancellationToken); // Wait for the request to be pushed to the queue
+                    cts.Cancel();
+
+                    await Task.Delay(10_000, cancellationToken);
+                    await s.ConnectAsync(ctx.DnsEndPoint, cancellationToken);
+                    connected = true;
+                    return new NetworkStream(s, ownsSocket: true);
+                }
+
+                Assert.True(connected);
+            }, timeout.ToString()).Dispose();
+        }
+    }
+}

src/libraries/System.Net.Http/tests/FunctionalTests/System.Net.Http.Functional.Tests.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <StringResourcesPath>../../src/Resources/Strings.resx</StringResourcesPath>
     <DefineConstants>$(DefineConstants);SYSNETHTTP_NO_OPENSSL;HTTP3</DefineConstants>
@@ -157,6 +157,7 @@
              Link="Common\TestUtilities\System\DisableParallelization.cs" />
     <Compile Include="HttpClientHandlerTest.AltSvc.cs" />
     <Compile Include="SocketsHttpHandlerTest.Cancellation.cs" />
+    <Compile Include="SocketsHttpHandlerTest.Cancellation.NonParallel.cs" />
     <Compile Include="SocketsHttpHandlerTest.Http2FlowControl.cs" />
     <Compile Include="SocketsHttpHandlerTest.Http2KeepAlivePing.cs" />
     <Compile Include="HttpClientHandlerTest.Connect.cs" />