Log 404 responses from long polling transport DELETE as Debug instead of Error (#2366)

src/Microsoft.AspNetCore.Http.Connections.Client/Internal/LongPollingTransport.Log.cs

@@ -53,6 +53,9 @@ namespace Microsoft.AspNetCore.Http.Connections.Client.Internal
             private static readonly Action<ILogger, Uri, Exception> _errorSendingDeleteRequest =
                 LoggerMessage.Define<Uri>(LogLevel.Error, new EventId(13, "ErrorSendingDeleteRequest"), "Error sending DELETE request to '{PollUrl}'.");
 
+            private static readonly Action<ILogger, Uri, Exception> _connectionAlreadyClosedSendingDeleteRequest =
+                LoggerMessage.Define<Uri>(LogLevel.Debug, new EventId(14, "ConnectionAlreadyClosedSendingDeleteRequest"), "A 404 response was returned from sending DELETE request to '{PollUrl}', likely because the transport was already closed on the server.");
+
             // EventIds 100 - 106 used in SendUtils
 
             public static void StartTransport(ILogger logger, TransferFormat transferFormat)
@@ -123,6 +126,11 @@ namespace Microsoft.AspNetCore.Http.Connections.Client.Internal
             {
                 _errorSendingDeleteRequest(logger, pollUrl, ex);
             }
+
+            public static void ConnectionAlreadyClosedSendingDeleteRequest(ILogger logger, Uri pollUrl)
+            {
+                _connectionAlreadyClosedSendingDeleteRequest(logger, pollUrl, null);
+            }
         }
     }
 }

src/Microsoft.AspNetCore.Http.Connections.Client/Internal/LongPollingTransport.cs

@@ -221,8 +221,17 @@ namespace Microsoft.AspNetCore.Http.Connections.Client.Internal
             {
                 Log.SendingDeleteRequest(_logger, url);
                 var response = await _httpClient.DeleteAsync(url);
-                response.EnsureSuccessStatusCode();
+
-                Log.DeleteRequestAccepted(_logger, url);
+                if (response.StatusCode == HttpStatusCode.NotFound)
+                {
+                    Log.ConnectionAlreadyClosedSendingDeleteRequest(_logger, url);
+                }
+                else
+                {
+                    // Check for non-404 errors
+                    response.EnsureSuccessStatusCode();
+                    Log.DeleteRequestAccepted(_logger, url);
+                }
             }
             catch (Exception ex)
             {

test/Microsoft.AspNetCore.SignalR.Client.Tests/LongPollingTransportTests.cs

@@ -17,16 +17,22 @@ using System.Threading.Tasks;
 using Microsoft.AspNetCore.Connections;
 using Microsoft.AspNetCore.Http.Connections.Client;
 using Microsoft.AspNetCore.Http.Connections.Client.Internal;
+using Microsoft.AspNetCore.SignalR.Tests;
 using Moq;
 using Moq.Protected;
 using Xunit;
+using Xunit.Abstractions;
 
 namespace Microsoft.AspNetCore.SignalR.Client.Tests
 {
-    public class LongPollingTransportTests
+    public class LongPollingTransportTests : VerifiableLoggedTest
     {
         private static readonly Uri TestUri = new Uri("http://example.com/?id=1234");
 
+        public LongPollingTransportTests(ITestOutputHelper output) : base(output)
+        {
+        }
+
         [Fact]
         public async Task LongPollingTransportStopsPollAndSendLoopsWhenTransportStopped()
         {
@@ -222,6 +228,53 @@ namespace Microsoft.AspNetCore.SignalR.Client.Tests
             }
         }
 
+        [Fact]
+        public async Task StopTransportWhenConnectionAlreadyStoppedOnServer()
+        {
+            var pollRequestTcs = new TaskCompletionSource<object>();
+
+            var mockHttpHandler = new Mock<HttpMessageHandler>();
+            var firstPoll = true;
+            mockHttpHandler.Protected()
+                .Setup<Task<HttpResponseMessage>>("SendAsync", ItExpr.IsAny<HttpRequestMessage>(), ItExpr.IsAny<CancellationToken>())
+                .Returns<HttpRequestMessage, CancellationToken>(async (request, cancellationToken) =>
+                {
+                    await Task.Yield();
+                    if (request.Method == HttpMethod.Delete)
+                    {
+                        // Simulate the server having already cleaned up the connection on the server
+                        return ResponseUtils.CreateResponse(HttpStatusCode.NotFound);
+                    }
+                    else
+                    {
+                        if (firstPoll)
+                        {
+                            firstPoll = false;
+                            return ResponseUtils.CreateResponse(HttpStatusCode.OK);
+                        }
+
+                        await pollRequestTcs.Task;
+                        return ResponseUtils.CreateResponse(HttpStatusCode.OK);
+                    }
+                });
+
+            using (StartVerifiableLog(out var loggerFactory))
+            {
+                using (var httpClient = new HttpClient(mockHttpHandler.Object))
+                {
+                    var longPollingTransport = new LongPollingTransport(httpClient, loggerFactory);
+
+                    await longPollingTransport.StartAsync(TestUri, TransferFormat.Binary).OrTimeout();
+
+                    var stopTask = longPollingTransport.StopAsync();
+
+                    pollRequestTcs.SetResult(null);
+
+                    await stopTask.OrTimeout();
+                }
+            }
+        }
+
         [Fact]
         public async Task LongPollingTransportStopsWhenSendRequestFails()
         {