Fix preserving messages for stateful reconnect with backplane

src/SignalR/common/Shared/MessageBuffer.cs

@@ -121,15 +121,16 @@ private async Task RunTimer()
 
     public ValueTask<FlushResult> WriteAsync(SerializedHubMessage hubMessage, CancellationToken cancellationToken)
     {
-        return WriteAsyncCore(hubMessage.Message!, hubMessage.GetSerializedMessage(_protocol), cancellationToken);
+        // Default to HubInvocationMessage as that's the only type we use SerializedHubMessage for currently. Should harden this in the future.
+        return WriteAsyncCore(hubMessage.Message?.GetType() ?? typeof(HubInvocationMessage), hubMessage.GetSerializedMessage(_protocol), cancellationToken);
     }
 
     public ValueTask<FlushResult> WriteAsync(HubMessage hubMessage, CancellationToken cancellationToken)
     {
-        return WriteAsyncCore(hubMessage, _protocol.GetMessageBytes(hubMessage), cancellationToken);
+        return WriteAsyncCore(hubMessage.GetType(), _protocol.GetMessageBytes(hubMessage), cancellationToken);
     }
 
-    private async ValueTask<FlushResult> WriteAsyncCore(HubMessage hubMessage, ReadOnlyMemory<byte> messageBytes, CancellationToken cancellationToken)
+    private async ValueTask<FlushResult> WriteAsyncCore(Type hubMessageType, ReadOnlyMemory<byte> messageBytes, CancellationToken cancellationToken)
     {
         // TODO: Add backpressure based on message count
         if (_bufferedByteCount > _bufferLimit)
@@ -158,7 +159,7 @@ private async ValueTask<FlushResult> WriteAsyncCore(HubMessage hubMessage, ReadO
         await _writeLock.WaitAsync(cancellationToken: default).ConfigureAwait(false);
         try
         {
-            if (hubMessage is HubInvocationMessage invocationMessage)
+            if (typeof(HubInvocationMessage).IsAssignableFrom(hubMessageType))
             {
                 _totalMessageCount++;
                 _bufferedByteCount += messageBytes.Length;

src/SignalR/server/Core/src/SerializedHubMessage.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics;
 using Microsoft.AspNetCore.SignalR.Protocol;
 
 namespace Microsoft.AspNetCore.SignalR;
@@ -40,6 +41,8 @@ public SerializedHubMessage(IReadOnlyList<SerializedMessage> messages)
     /// <param name="message">The hub message for the cache. This will be serialized with an <see cref="IHubProtocol"/> in <see cref="GetSerializedMessage"/> to get the message's serialized representation.</param>
     public SerializedHubMessage(HubMessage message)
     {
+        // Type currently only used for invocation messages, we should probably refactor it to be explicit about that e.g. new property for message type?
+        Debug.Assert(message.GetType().IsAssignableTo(typeof(HubInvocationMessage)));
         Message = message;
     }
 

src/SignalR/server/SignalR/test/Microsoft.AspNetCore.SignalR.Tests/Internal/MessageBufferTests.cs

@@ -2,11 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.IO.Pipelines;
+using System.Text.Json;
 using Microsoft.AspNetCore.Connections;
 using Microsoft.AspNetCore.Http.Features;
+using Microsoft.AspNetCore.InternalTesting;
 using Microsoft.AspNetCore.SignalR.Internal;
 using Microsoft.AspNetCore.SignalR.Protocol;
-using Microsoft.AspNetCore.InternalTesting;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Time.Testing;
 
@@ -169,6 +170,62 @@ public async Task UnAckedMessageResentOnReconnect()
         Assert.False(messageBuffer.ShouldProcessMessage(CompletionMessage.WithResult("1", null)));
     }
 
+    // Regression test for https://github.com/dotnet/aspnetcore/issues/55575
+    [Fact]
+    public async Task UnAckedSerializedMessageResentOnReconnect()
+    {
+        var protocol = new JsonHubProtocol();
+        var connection = new TestConnectionContext();
+        var pipes = DuplexPipe.CreateConnectionPair(new PipeOptions(), new PipeOptions());
+        connection.Transport = pipes.Transport;
+        using var messageBuffer = new MessageBuffer(connection, protocol, bufferLimit: 1000, NullLogger.Instance);
+
+        var invocationMessage = new SerializedHubMessage([new SerializedMessage(protocol.Name,
+            protocol.GetMessageBytes(new InvocationMessage("method1", [1])))]);
+        await messageBuffer.WriteAsync(invocationMessage, default);
+
+        var res = await pipes.Application.Input.ReadAsync();
+
+        var buffer = res.Buffer;
+        Assert.True(protocol.TryParseMessage(ref buffer, new TestBinder(), out var message));
+        var parsedMessage = Assert.IsType<InvocationMessage>(message);
+        Assert.Equal("method1", parsedMessage.Target);
+        Assert.Equal(1, ((JsonElement)Assert.Single(parsedMessage.Arguments)).GetInt32());
+
+        pipes.Application.Input.AdvanceTo(buffer.Start);
+
+        DuplexPipe.UpdateConnectionPair(ref pipes, connection);
+        await messageBuffer.ResendAsync(pipes.Transport.Output);
+
+        Assert.True(messageBuffer.ShouldProcessMessage(PingMessage.Instance));
+        Assert.True(messageBuffer.ShouldProcessMessage(CompletionMessage.WithResult("1", null)));
+        Assert.True(messageBuffer.ShouldProcessMessage(new SequenceMessage(1)));
+
+        res = await pipes.Application.Input.ReadAsync();
+
+        buffer = res.Buffer;
+        Assert.True(protocol.TryParseMessage(ref buffer, new TestBinder(), out message));
+        var seqMessage = Assert.IsType<SequenceMessage>(message);
+        Assert.Equal(1, seqMessage.SequenceId);
+
+        pipes.Application.Input.AdvanceTo(buffer.Start);
+
+        res = await pipes.Application.Input.ReadAsync();
+
+        buffer = res.Buffer;
+        Assert.True(protocol.TryParseMessage(ref buffer, new TestBinder(), out message));
+        parsedMessage = Assert.IsType<InvocationMessage>(message);
+        Assert.Equal("method1", parsedMessage.Target);
+        Assert.Equal(1, ((JsonElement)Assert.Single(parsedMessage.Arguments)).GetInt32());
+
+        pipes.Application.Input.AdvanceTo(buffer.Start);
+
+        messageBuffer.ShouldProcessMessage(new SequenceMessage(1));
+
+        Assert.True(messageBuffer.ShouldProcessMessage(PingMessage.Instance));
+        Assert.False(messageBuffer.ShouldProcessMessage(CompletionMessage.WithResult("1", null)));
+    }
+
     [Fact]
     public async Task AckedMessageNotResentOnReconnect()
     {

src/SignalR/server/StackExchangeRedis/test/RedisEndToEnd.cs

@@ -1,17 +1,15 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System;
-using System.Collections.Generic;
-using System.Threading.Tasks;
+using System.Net.WebSockets;
 using Microsoft.AspNetCore.Http.Connections;
+using Microsoft.AspNetCore.Http.Connections.Client;
+using Microsoft.AspNetCore.InternalTesting;
 using Microsoft.AspNetCore.SignalR.Client;
 using Microsoft.AspNetCore.SignalR.Protocol;
 using Microsoft.AspNetCore.SignalR.Tests;
-using Microsoft.AspNetCore.InternalTesting;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
-using Xunit;
 
 namespace Microsoft.AspNetCore.SignalR.StackExchangeRedis.Tests;
 
@@ -213,7 +211,105 @@ public async Task CanSendAndReceiveUserMessagesUserNameWithPatternIsTreatedAsLit
         }
     }
 
-    private static HubConnection CreateConnection(string url, HttpTransportType transportType, IHubProtocol protocol, ILoggerFactory loggerFactory, string userName = null)
+    [ConditionalTheory]
+    [SkipIfDockerNotPresent]
+    [InlineData("messagepack")]
+    [InlineData("json")]
+    public async Task StatefulReconnectPreservesMessageFromOtherServer(string protocolName)
+    {
+        using (StartVerifiableLog())
+        {
+            var protocol = HubProtocolHelpers.GetHubProtocol(protocolName);
+
+            ClientWebSocket innerWs = null;
+            WebSocketWrapper ws = null;
+            TaskCompletionSource reconnectTcs = null;
+            TaskCompletionSource startedReconnectTcs = null;
+
+            var connection = CreateConnection(_serverFixture.FirstServer.Url + "/stateful", HttpTransportType.WebSockets, protocol, LoggerFactory,
+                customizeConnection: builder =>
+                {
+                    builder.WithStatefulReconnect();
+                    builder.Services.Configure<HttpConnectionOptions>(o =>
+                    {
+                        // Replace the websocket creation for the first connection so we can make the client think there was an ungraceful closure
+                        // Which will trigger the stateful reconnect flow
+                        o.WebSocketFactory = async (context, token) =>
+                        {
+                            if (reconnectTcs is null)
+                            {
+                                reconnectTcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+                                startedReconnectTcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+                            }
+                            else
+                            {
+                                startedReconnectTcs.SetResult();
+                                // We only want to wait on the reconnect, not the initial connection attempt
+                                await reconnectTcs.Task.DefaultTimeout();
+                            }
+
+                            innerWs = new ClientWebSocket();
+                            ws = new WebSocketWrapper(innerWs);
+                            await innerWs.ConnectAsync(context.Uri, token);
+
+                            _ = Task.Run(async () =>
+                            {
+                                try
+                                {
+                                    while (innerWs.State == WebSocketState.Open)
+                                    {
+                                        var buffer = new byte[1024];
+                                        var res = await innerWs.ReceiveAsync(buffer, default);
+                                        ws.SetReceiveResult((res, buffer.AsMemory(0, res.Count)));
+                                    }
+                                }
+                                // Log but ignore receive errors, that likely just means the connection closed
+                                catch (Exception ex)
+                                {
+                                    Logger.LogInformation(ex, "Error while reading from inner websocket");
+                                }
+                            });
+
+                            return ws;
+                        };
+                    });
+                });
+            var secondConnection = CreateConnection(_serverFixture.SecondServer.Url + "/stateful", HttpTransportType.WebSockets, protocol, LoggerFactory);
+
+            var tcs = new TaskCompletionSource<string>();
+            connection.On<string>("SendToAll", message => tcs.TrySetResult(message));
+
+            var tcs2 = new TaskCompletionSource<string>();
+            secondConnection.On<string>("SendToAll", message => tcs2.TrySetResult(message));
+
+            await connection.StartAsync().DefaultTimeout();
+            await secondConnection.StartAsync().DefaultTimeout();
+
+            // Close first connection before the second connection sends a message to all clients
+            await ws.CloseOutputAsync(WebSocketCloseStatus.InternalServerError, statusDescription: null, default);
+            await startedReconnectTcs.Task.DefaultTimeout();
+
+            // Send to all clients, since both clients are on different servers this means the backplane will be used
+            // And we want to test that messages are still preserved for stateful reconnect purposes when a client disconnects
+            // But is on a different server from the original message sender.
+            await secondConnection.SendAsync("SendToAll", "test message").DefaultTimeout();
+
+            // Check that second connection still receives the message
+            Assert.Equal("test message", await tcs2.Task.DefaultTimeout());
+            Assert.False(tcs.Task.IsCompleted);
+
+            // allow first connection to reconnect
+            reconnectTcs.SetResult();
+
+            // Check that first connection received the message once it reconnected
+            Assert.Equal("test message", await tcs.Task.DefaultTimeout());
+
+            await connection.DisposeAsync().DefaultTimeout();
+        }
+    }
+
+    private static HubConnection CreateConnection(string url, HttpTransportType transportType, IHubProtocol protocol, ILoggerFactory loggerFactory, string userName = null,
+        Action<IHubConnectionBuilder> customizeConnection = null)
     {
         var hubConnectionBuilder = new HubConnectionBuilder()
             .WithLoggerFactory(loggerFactory)
@@ -227,6 +323,8 @@ private static HubConnection CreateConnection(string url, HttpTransportType tran
 
         hubConnectionBuilder.Services.AddSingleton(protocol);
 
+        customizeConnection?.Invoke(hubConnectionBuilder);
+
         return hubConnectionBuilder.Build();
     }
 
@@ -255,4 +353,67 @@ public static IEnumerable<object[]> TransportTypesAndProtocolTypes
             }
         }
     }
+
+    internal sealed class WebSocketWrapper : WebSocket
+    {
+        private readonly WebSocket _inner;
+        private TaskCompletionSource<(WebSocketReceiveResult, ReadOnlyMemory<byte>)> _receiveTcs = new(TaskCreationOptions.RunContinuationsAsynchronously);
+
+        public WebSocketWrapper(WebSocket inner)
+        {
+            _inner = inner;
+        }
+
+        public override WebSocketCloseStatus? CloseStatus => _inner.CloseStatus;
+
+        public override string CloseStatusDescription => _inner.CloseStatusDescription;
+
+        public override WebSocketState State => _inner.State;
+
+        public override string SubProtocol => _inner.SubProtocol;
+
+        public override void Abort()
+        {
+            _inner.Abort();
+        }
+
+        public override Task CloseAsync(WebSocketCloseStatus closeStatus, string statusDescription, CancellationToken cancellationToken)
+        {
+            return _inner.CloseAsync(closeStatus, statusDescription, cancellationToken);
+        }
+
+        public override Task CloseOutputAsync(WebSocketCloseStatus closeStatus, string statusDescription, CancellationToken cancellationToken)
+        {
+            _receiveTcs.TrySetException(new IOException("force reconnect"));
+            return Task.CompletedTask;
+        }
+
+        public override void Dispose()
+        {
+            _inner.Dispose();
+        }
+
+        public void SetReceiveResult((WebSocketReceiveResult, ReadOnlyMemory<byte>) result)
+        {
+            _receiveTcs.SetResult(result);
+        }
+
+        public override async Task<WebSocketReceiveResult> ReceiveAsync(ArraySegment<byte> buffer, CancellationToken cancellationToken)
+        {
+            var res = await _receiveTcs.Task;
+            // Handle zero-byte reads
+            if (buffer.Count == 0)
+            {
+                return res.Item1;
+            }
+            _receiveTcs = new(TaskCreationOptions.RunContinuationsAsynchronously);
+            res.Item2.CopyTo(buffer);
+            return res.Item1;
+        }
+
+        public override Task SendAsync(ArraySegment<byte> buffer, WebSocketMessageType messageType, bool endOfMessage, CancellationToken cancellationToken)
+        {
+            return _inner.SendAsync(buffer, messageType, endOfMessage, cancellationToken);
+        }
+    }
 }

src/SignalR/server/StackExchangeRedis/test/Startup.cs

@@ -33,6 +33,7 @@ public void Configure(IApplicationBuilder app)
         app.UseEndpoints(endpoints =>
         {
             endpoints.MapHub<EchoHub>("/echo");
+            endpoints.MapHub<StatefulHub>("/stateful", o => o.AllowStatefulReconnects = true);
         });
     }
 

src/SignalR/server/StackExchangeRedis/test/StatefulHub.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.SignalR.StackExchangeRedis.Tests;
+
+public class StatefulHub : Hub
+{
+    public Task SendToAll(string message)
+    {
+        return Clients.All.SendAsync("SendToAll", message);
+    }
+}