#2035 Do not await OnCompleted handlers before sending the Response (#2324)

src/Kestrel.Core/Internal/Http/HttpProtocol.cs

@@ -554,11 +554,6 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 
                 PauseStreams();
 
-                if (_onCompleted != null)
-                {
-                    await FireOnCompleted();
-                }
-
                 if (badRequestException == null)
                 {
                     // If _requestAbort is set, the connection has already been closed.
@@ -601,6 +596,11 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                     }
                 }
 
+                if (_onCompleted != null)
+                {
+                    await FireOnCompleted();
+                }
+
                 if (badRequestException != null)
                 {
                     // Handle BadHttpRequestException thrown during app execution or remaining message body consumption.
@@ -739,10 +739,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             {
                 return Task.CompletedTask;
             }
-            else
+
-            {
+            return FireOnCompletedAwaited(onCompleted);
-                return FireOnCompletedAwaited(onCompleted);
-            }
         }
 
         private async Task FireOnCompletedAwaited(Stack<KeyValuePair<Func<object, Task>, object>> onCompleted)
@@ -755,7 +753,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                 }
                 catch (Exception ex)
                 {
-                    ReportApplicationError(ex);
+                    Log.ApplicationError(ConnectionId, TraceIdentifier, ex);
                 }
             }
         }

test/Kestrel.FunctionalTests/ResponseTests.cs

@@ -146,7 +146,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
         public async Task OnCompleteCalledEvenWhenOnStartingNotCalled()
         {
             var onStartingCalled = false;
-            var onCompletedCalled = false;
+            var onCompletedTcs = new TaskCompletionSource<object>();
 
             var hostBuilder = TransportSelector.GetWebHostBuilder()
                 .UseKestrel()
@@ -156,7 +156,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
                     app.Run(context =>
                     {
                         context.Response.OnStarting(() => Task.Run(() => onStartingCalled = true));
-                        context.Response.OnCompleted(() => Task.Run(() => onCompletedCalled = true));
+                        context.Response.OnCompleted(() => Task.Run(() =>
+                        {
+                            onCompletedTcs.SetResult(null);
+                        }));
 
                         // Prevent OnStarting call (see HttpProtocol.ProcessRequestsAsync()).
                         throw new Exception();
@@ -173,7 +176,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
 
                     Assert.Equal(HttpStatusCode.InternalServerError, response.StatusCode);
                     Assert.False(onStartingCalled);
-                    Assert.True(onCompletedCalled);
+                    await onCompletedTcs.Task.TimeoutAfter(TestConstants.DefaultTimeout);
                 }
             }
         }
@@ -294,6 +297,99 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
                 sendMalformedRequest: true);
         }
 
+        [Fact]
+        public async Task OnCompletedExceptionShouldNotPreventAResponse()
+        {
+            var hostBuilder = TransportSelector.GetWebHostBuilder()
+                .UseKestrel()
+                .UseUrls("http://127.0.0.1:0/")
+                .Configure(app =>
+                {
+                    app.Run(async context =>
+                    {
+                        context.Response.OnCompleted(_ => throw new Exception(), null);
+                        await context.Response.WriteAsync("hello, world");
+                    });
+                });
+
+            using (var host = hostBuilder.Build())
+            {
+                host.Start();
+
+                using (var client = new HttpClient())
+                {
+                    var response = await client.GetAsync($"http://127.0.0.1:{host.GetPort()}/");
+                    Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+                }
+            }
+        }
+
+        [Fact]
+        public async Task OnCompletedShouldNotBlockAResponse()
+        {
+            var delay = Task.Delay(TestConstants.DefaultTimeout);
+            var hostBuilder = TransportSelector.GetWebHostBuilder()
+                .UseKestrel()
+                .UseUrls("http://127.0.0.1:0/")
+                .Configure(app =>
+                {
+                    app.Run(async context =>
+                    {
+                        context.Response.OnCompleted(async () =>
+                        {
+                            await delay;
+                        });
+                        await context.Response.WriteAsync("hello, world");
+                    });
+                });
+
+            using (var host = hostBuilder.Build())
+            {
+                host.Start();
+
+                using (var client = new HttpClient())
+                {
+                    var response = await client.GetAsync($"http://127.0.0.1:{host.GetPort()}/");
+                    Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+                    Assert.False(delay.IsCompleted);
+                }
+            }
+        }
+
+        [Fact]
+        public async Task InvalidChunkedEncodingInRequestShouldNotBlockOnCompleted()
+        {
+            var onCompletedTcs = new TaskCompletionSource<object>();
+
+            using (var server = new TestServer(httpContext =>
+            {
+                httpContext.Response.OnCompleted(() => Task.Run(() =>
+                {
+                    onCompletedTcs.SetResult(null);
+                }));
+                return Task.CompletedTask;
+            }))
+            {
+                using (var connection = server.CreateConnection())
+                {
+                    await connection.Send(
+                        "GET / HTTP/1.1",
+                        "Host:",
+                        "Transfer-Encoding: chunked",
+                        "",
+                        "gg");
+                    await connection.ReceiveForcedEnd(
+                        "HTTP/1.1 200 OK",
+                        $"Date: {server.Context.DateHeaderValue}",
+                        "Content-Length: 0",
+                        "",
+                        "");
+                }
+            }
+
+            await onCompletedTcs.Task.TimeoutAfter(TestConstants.DefaultTimeout);
+        }
+
         private static async Task ResponseStatusCodeSetBeforeHttpContextDispose(
             RequestDelegate handler,
             HttpStatusCode? expectedClientStatusCode,
@@ -1988,7 +2084,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
 
         [Theory]
         [MemberData(nameof(ConnectionAdapterData))]
-        public async Task ThrowingInOnCompletedIsLoggedAndClosesConnection(ListenOptions listenOptions)
+        public async Task ThrowingInOnCompletedIsLogged(ListenOptions listenOptions)
         {
             var testContext = new TestServiceContext();
 
@@ -2024,7 +2120,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
                         "Host:",
                         "",
                         "");
-                    await connection.ReceiveForcedEnd(
+                    await connection.ReceiveEnd(
                         "HTTP/1.1 200 OK",
                         $"Date: {testContext.DateHeaderValue}",
                         "Content-Length: 11",