Correctly check socket on stream creation

src/Grpc.Net.Client/Balancer/Internal/SocketConnectivitySubchannelTransport.cs

@@ -253,53 +253,7 @@ private void OnCheckSocketConnection(object? state)
                 {
                     CompatibilityHelpers.Assert(socketAddress != null);
 
-                    try
-                    {
-                        SocketConnectivitySubchannelTransportLog.CheckingSocket(_logger, _subchannel.Id, socketAddress);
-
-                        // Poll socket to check if it can be read from. Unfortunatly this requires reading pending data.
-                        // The server might send data, e.g. HTTP/2 SETTINGS frame, so we need to read and cache it.
-                        //
-                        // Available data needs to be read now because the only way to determine whether the connection is closed is to
-                        // get the results of polling after available data is received.
-                        bool hasReadData;
-                        do
-                        {
-                            closeSocket = IsSocketInBadState(socket, socketAddress);
-                            var available = socket.Available;
-                            if (available > 0)
-                            {
-                                hasReadData = true;
-                                var serverDataAvailable = CalculateInitialSocketDataLength(_initialSocketData) + available;
-                                if (serverDataAvailable > MaximumInitialSocketDataSize)
-                                {
-                                    // Data sent to the client before a connection is started shouldn't be large.
-                                    // Put a maximum limit on the buffer size to prevent an unexpected scenario from consuming too much memory.
-                                    throw new InvalidOperationException($"The server sent {serverDataAvailable} bytes to the client before a connection was established. Maximum allowed data exceeded.");
-                                }
-
-                                SocketConnectivitySubchannelTransportLog.SocketReceivingAvailable(_logger, _subchannel.Id, socketAddress, available);
-
-                                // Data is already available so this won't block.
-                                var buffer = new byte[available];
-                                var readCount = socket.Receive(buffer);
-
-                                _initialSocketData ??= new List<ReadOnlyMemory<byte>>();
-                                _initialSocketData.Add(buffer.AsMemory(0, readCount));
-                            }
-                            else
-                            {
-                                hasReadData = false;
-                            }
-                        }
-                        while (hasReadData);
-                    }
-                    catch (Exception ex)
-                    {
-                        closeSocket = true;
-                        checkException = ex;
-                        SocketConnectivitySubchannelTransportLog.ErrorCheckingSocket(_logger, _subchannel.Id, socketAddress, ex);
-                    }
+                    closeSocket = CheckSocket(socket, socketAddress, ref _initialSocketData, out checkException);
                 }
             }
 
@@ -337,6 +291,68 @@ private void OnCheckSocketConnection(object? state)
         }
     }
 
+    /// <summary>
+    /// Checks whether the socket is healthy. May read available data into the passed in buffer.
+    /// Returns true if the socket should be closed.
+    /// </summary>
+    private bool CheckSocket(Socket socket, BalancerAddress socketAddress, ref List<ReadOnlyMemory<byte>>? socketData, out Exception? checkException)
+    {
+        checkException = null;
+
+        try
+        {
+            SocketConnectivitySubchannelTransportLog.CheckingSocket(_logger, _subchannel.Id, socketAddress);
+
+            // Poll socket to check if it can be read from. Unfortunatly this requires reading pending data.
+            // The server might send data, e.g. HTTP/2 SETTINGS frame, so we need to read and cache it.
+            //
+            // Available data needs to be read now because the only way to determine whether the connection is closed is to
+            // get the results of polling after available data is received.
+            bool hasReadData;
+            do
+            {
+                if (IsSocketInBadState(socket, socketAddress))
+                {
+                    return true;
+                }
+
+                var available = socket.Available;
+                if (available > 0)
+                {
+                    hasReadData = true;
+                    var serverDataAvailable = CalculateInitialSocketDataLength(socketData) + available;
+                    if (serverDataAvailable > MaximumInitialSocketDataSize)
+                    {
+                        // Data sent to the client before a connection is started shouldn't be large.
+                        // Put a maximum limit on the buffer size to prevent an unexpected scenario from consuming too much memory.
+                        throw new InvalidOperationException($"The server sent {serverDataAvailable} bytes to the client before a connection was established. Maximum allowed data exceeded.");
+                    }
+
+                    SocketConnectivitySubchannelTransportLog.SocketReceivingAvailable(_logger, _subchannel.Id, socketAddress, available);
+
+                    // Data is already available so this won't block.
+                    var buffer = new byte[available];
+                    var readCount = socket.Receive(buffer);
+
+                    socketData ??= new List<ReadOnlyMemory<byte>>();
+                    socketData.Add(buffer.AsMemory(0, readCount));
+                }
+                else
+                {
+                    hasReadData = false;
+                }
+            }
+            while (hasReadData);
+            return false;
+        }
+        catch (Exception ex)
+        {
+            checkException = ex;
+            SocketConnectivitySubchannelTransportLog.ErrorCheckingSocket(_logger, _subchannel.Id, socketAddress, ex);
+            return true;
+        }
+    }
+
     public async ValueTask<Stream> GetStreamAsync(BalancerAddress address, CancellationToken cancellationToken)
     {
         SocketConnectivitySubchannelTransportLog.CreatingStream(_logger, _subchannel.Id, address);
@@ -383,7 +399,7 @@ public async ValueTask<Stream> GetStreamAsync(BalancerAddress address, Cancellat
                 SocketConnectivitySubchannelTransportLog.ClosingSocketFromIdleTimeoutOnCreateStream(_logger, _subchannel.Id, address, _socketIdleTimeout);
                 closeSocket = true;
             }
-            else if (IsSocketInBadState(socket, address))
+            else if (CheckSocket(socket, address, ref socketData, out _))
             {
                 SocketConnectivitySubchannelTransportLog.ClosingUnusableSocketOnCreateStream(_logger, _subchannel.Id, address);
                 closeSocket = true;

test/FunctionalTests/Balancer/BalancerHelpers.cs

@@ -54,11 +54,12 @@ public static EndpointContext<TRequest, TResponse> CreateGrpcEndpoint<TRequest,
         HttpProtocols? protocols = null,
         bool? isHttps = null,
         X509Certificate2? certificate = null,
-        ILoggerFactory? loggerFactory = null)
+        ILoggerFactory? loggerFactory = null,
+        Action<KestrelServerOptions>? configureServer = null)
         where TRequest : class, IMessage, new()
         where TResponse : class, IMessage, new()
     {
-        var server = CreateServer(port, protocols, isHttps, certificate, loggerFactory);
+        var server = CreateServer(port, protocols, isHttps, certificate, loggerFactory, configureServer);
         var method = server.DynamicGrpc.AddUnaryMethod(callHandler, methodName);
         var url = server.GetUrl(isHttps.GetValueOrDefault(false) ? TestServerEndpointName.Http2WithTls : TestServerEndpointName.Http2);
 
@@ -88,7 +89,13 @@ public void Dispose()
         }
     }
 
-    public static GrpcTestFixture<Startup> CreateServer(int port, HttpProtocols? protocols = null, bool? isHttps = null, X509Certificate2? certificate = null, ILoggerFactory? loggerFactory = null)
+    public static GrpcTestFixture<Startup> CreateServer(
+        int port,
+        HttpProtocols? protocols = null,
+        bool? isHttps = null,
+        X509Certificate2? certificate = null,
+        ILoggerFactory? loggerFactory = null,
+        Action<KestrelServerOptions>? configureServer = null)
     {
         var endpointName = isHttps.GetValueOrDefault(false) ? TestServerEndpointName.Http2WithTls : TestServerEndpointName.Http2;
 
@@ -102,6 +109,8 @@ public static GrpcTestFixture<Startup> CreateServer(int port, HttpProtocols? pro
             },
             (options, urls) =>
             {
+                configureServer?.Invoke(options);
+
                 urls[endpointName] = isHttps.GetValueOrDefault(false)
                     ? $"https://127.0.0.1:{port}"
                     : $"http://127.0.0.1:{port}";
@@ -136,13 +145,14 @@ public static Task<GrpcChannel> CreateChannel(
         RetryPolicy? retryPolicy = null,
         Func<Socket, DnsEndPoint, CancellationToken, ValueTask>? socketConnect = null,
         TimeSpan? connectTimeout = null,
-        TimeSpan? connectionIdleTimeout = null)
+        TimeSpan? connectionIdleTimeout = null,
+        TimeSpan? socketPingInterval = null)
     {
         var resolver = new TestResolver();
         var e = endpoints.Select(i => new BalancerAddress(i.Host, i.Port)).ToList();
         resolver.UpdateAddresses(e);
 
-        return CreateChannel(loggerFactory, loadBalancingConfig, resolver, httpMessageHandler, connect, retryPolicy, socketConnect, connectTimeout, connectionIdleTimeout);
+        return CreateChannel(loggerFactory, loadBalancingConfig, resolver, httpMessageHandler, connect, retryPolicy, socketConnect, connectTimeout, connectionIdleTimeout, socketPingInterval);
     }
 
     public static async Task<GrpcChannel> CreateChannel(
@@ -154,12 +164,13 @@ public static async Task<GrpcChannel> CreateChannel(
         RetryPolicy? retryPolicy = null,
         Func<Socket, DnsEndPoint, CancellationToken, ValueTask>? socketConnect = null,
         TimeSpan? connectTimeout = null,
-        TimeSpan? connectionIdleTimeout = null)
+        TimeSpan? connectionIdleTimeout = null,
+        TimeSpan? socketPingInterval = null)
     {
         var services = new ServiceCollection();
         services.AddSingleton<ResolverFactory>(new TestResolverFactory(resolver));
         services.AddSingleton<IRandomGenerator>(new TestRandomGenerator());
-        services.AddSingleton<ISubchannelTransportFactory>(new TestSubchannelTransportFactory(TimeSpan.FromSeconds(0.5), connectTimeout, connectionIdleTimeout ?? TimeSpan.FromMinutes(1), socketConnect));
+        services.AddSingleton<ISubchannelTransportFactory>(new TestSubchannelTransportFactory(socketPingInterval ?? TimeSpan.FromSeconds(0.5), connectTimeout, connectionIdleTimeout ?? TimeSpan.FromMinutes(1), socketConnect));
         services.AddSingleton<LoadBalancerFactory>(new LeastUsedBalancerFactory());
 
         var serviceConfig = new ServiceConfig();

test/FunctionalTests/Balancer/ConnectionTests.cs

@@ -156,7 +156,7 @@ Task<HelloReply> UnaryMethod(HelloRequest request, ServerCallContext context)
         }
 
         // Arrange
-        using var endpoint = BalancerHelpers.CreateGrpcEndpoint<HelloRequest, HelloReply>(50051, UnaryMethod, nameof(UnaryMethod));
+        using var endpoint = BalancerHelpers.CreateGrpcEndpoint<HelloRequest, HelloReply>(50051, UnaryMethod, nameof(UnaryMethod), loggerFactory: LoggerFactory);
 
         var connectionIdleTimeout = TimeSpan.FromSeconds(1);
         var channel = await BalancerHelpers.CreateChannel(
@@ -180,6 +180,55 @@ Task<HelloReply> UnaryMethod(HelloRequest request, ServerCallContext context)
         AssertHasLog(LogLevel.Trace, "ConnectingOnCreateStream", "Subchannel id '1' doesn't have a connected socket available. Connecting new stream socket for 127.0.0.1:50051.");
     }
 
+    [Test]
+    public async Task Active_UnaryCall_ServerCloseOnKeepAlive_SocketRecreatedOnRequest()
+    {
+        // Ignore errors
+        SetExpectedErrorsFilter(writeContext =>
+        {
+            return true;
+        });
+
+        Task<HelloReply> UnaryMethod(HelloRequest request, ServerCallContext context)
+        {
+            return Task.FromResult(new HelloReply { Message = request.Name });
+        }
+
+        // In this test the client connects to the server, and the server then closes it after keep-alive is triggered.
+        // The client then starts a gRPC call to the server. The client should discard the closed socket and create a new one.
+
+        // Arrange
+        using var endpoint = BalancerHelpers.CreateGrpcEndpoint<HelloRequest, HelloReply>(
+            50051,
+            UnaryMethod,
+            nameof(UnaryMethod),
+            loggerFactory: LoggerFactory,
+            configureServer: o => o.Limits.KeepAliveTimeout = TimeSpan.FromSeconds(1));
+
+        // Don't timeout the socket or ping it from the client.
+        var channel = await BalancerHelpers.CreateChannel(
+            LoggerFactory,
+            new RoundRobinConfig(),
+            new[] { endpoint.Address },
+            connectionIdleTimeout: TimeSpan.FromMinutes(30),
+            socketPingInterval: TimeSpan.FromMinutes(30)).DefaultTimeout();
+
+        Logger.LogInformation("Connecting channel.");
+        await channel.ConnectAsync();
+
+        // Fails when this test is run with debugging. Kestrel doesn't trigger keepalive timeout if debugging is enabled.
+        await TestHelpers.AssertIsTrueRetryAsync(() =>
+        {
+            return Logs.Any(l => l.LoggerName.StartsWith("Microsoft.AspNetCore.Server.Kestrel") && l.EventId.Name == "ConnectionStop");
+        }, "Wait for server to close connection.");
+
+        var client = TestClientFactory.Create(channel, endpoint.Method);
+        var response = await client.UnaryCall(new HelloRequest { Name = "Test!" }).ResponseAsync.DefaultTimeout();
+
+        // Assert
+        Assert.AreEqual("Test!", response.Message);
+    }
+
     [Test]
     public async Task Active_UnaryCall_MultipleStreams_UnavailableAddress_FallbackToWorkingAddress()
     {