Fix using disposed token in connect and resulting status (#1873)

Author: JamesNK

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

@@ -18,6 +18,7 @@
 
 #if SUPPORT_LOAD_BALANCING
 using System;
+using System.Diagnostics;
 using Grpc.Core;
 
 namespace Grpc.Net.Client.Balancer.Internal
@@ -28,6 +29,7 @@ internal class ErrorPicker : SubchannelPicker
 
         public ErrorPicker(Status status)
         {
+            Debug.Assert(status.StatusCode != StatusCode.OK, "Error status code must not be OK.");
             _status = status;
         }
 

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

@@ -46,18 +46,22 @@ internal interface ISubchannelTransport : IDisposable
     internal sealed class ConnectContext
     {
         private readonly CancellationTokenSource _cts;
+        private readonly CancellationToken _token;
         private bool _disposed;
 
         // This flag allows the transport to determine why the cancellation token was canceled.
         // - Explicit cancellation, e.g. the channel was disposed.
         // - Connection timeout, e.g. SocketsHttpHandler.ConnectTimeout was exceeded.
         public bool IsConnectCanceled { get; private set; }
 
-        public CancellationToken CancellationToken => _cts.Token;
+        public CancellationToken CancellationToken => _token;
 
         public ConnectContext(TimeSpan connectTimeout)
         {
             _cts = new CancellationTokenSource(connectTimeout);
+
+            // Take a copy of the token to avoid ObjectDisposedException when accessing _cts.Token after CTS is disposed.
+            _token = _cts.Token;
         }
 
         public void CancelConnect()

src/Grpc.Net.Client/Balancer/Subchannel.cs

@@ -313,7 +313,7 @@ private async Task ConnectTransportAsync()
             {
                 SubchannelLog.ConnectError(_logger, Id, ex);
 
-                UpdateConnectivityState(ConnectivityState.TransientFailure, "Error connecting to subchannel.");
+                UpdateConnectivityState(ConnectivityState.TransientFailure, new Status(StatusCode.Unavailable, "Error connecting to subchannel.", ex));
             }
             finally
             {

test/Grpc.Net.Client.Tests/Balancer/ConnectionManagerTests.cs

@@ -144,6 +144,43 @@ public async Task PickAsync_WaitForReadyWithDrop_ThrowsError()
             Assert.AreEqual(StatusCode.DataLoss, ex.StatusCode);
         }
 
+        [Test]
+        public async Task PickAsync_ErrorConnectingToSubchannel_ThrowsError()
+        {
+            // Arrange
+            var services = new ServiceCollection();
+            services.AddNUnitLogger();
+            var serviceProvider = services.BuildServiceProvider();
+            var loggerFactory = serviceProvider.GetRequiredService<ILoggerFactory>();
+
+            var resolver = new TestResolver(loggerFactory);
+            resolver.UpdateAddresses(new List<BalancerAddress>
+            {
+                new BalancerAddress("localhost", 80)
+            });
+
+            var transportFactory = new TestSubchannelTransportFactory((s, c) =>
+            {
+                return Task.FromException<ConnectivityState>(new Exception("Test error!"));
+            });
+            var clientChannel = CreateConnectionManager(loggerFactory, resolver, transportFactory);
+            clientChannel.ConfigureBalancer(c => new PickFirstBalancer(c, loggerFactory));
+
+            // Act
+            _ = clientChannel.ConnectAsync(waitForReady: false, CancellationToken.None).ConfigureAwait(false);
+
+            var pickTask = clientChannel.PickAsync(
+                new PickContext { Request = new HttpRequestMessage() },
+                waitForReady: false,
+                CancellationToken.None).AsTask();
+
+            // Assert
+            var ex = await ExceptionAssert.ThrowsAsync<RpcException>(() => pickTask).DefaultTimeout();
+            Assert.AreEqual(StatusCode.Unavailable, ex.StatusCode);
+            Assert.AreEqual("Error connecting to subchannel.", ex.Status.Detail);
+            Assert.AreEqual("Test error!", ex.Status.DebugException?.Message);
+        }
+
         [Test]
         public async Task PickAsync_RetryWithDrop_ThrowsError()
         {

test/Grpc.Net.Client.Tests/GrpcChannelTests.cs

@@ -626,6 +626,7 @@ public async Task ConnectAsync_ShiftThroughStates_CompleteOnReady()
             var currentConnectivityState = ConnectivityState.TransientFailure;
 
             var services = new ServiceCollection();
+            services.AddNUnitLogger();
             services.AddSingleton<ResolverFactory, ChannelTestResolverFactory>();
             services.AddSingleton<ISubchannelTransportFactory>(new TestSubchannelTransportFactory(async (s, c) =>
             {

test/Grpc.Net.Client.Tests/Infrastructure/Balancer/TestSubChannelTransport.cs

@@ -81,7 +81,8 @@ public async
             var newState = await (_onTryConnect?.Invoke(context.CancellationToken) ?? Task.FromResult(ConnectivityState.Ready));
 
             CurrentAddress = Subchannel._addresses[0];
-            Subchannel.UpdateConnectivityState(newState, Status.DefaultSuccess);
+            var newStatus = newState == ConnectivityState.TransientFailure ? new Status(StatusCode.Internal, "") : Status.DefaultSuccess;
+            Subchannel.UpdateConnectivityState(newState, newStatus);
 
             _connectTcs.TrySetResult(null);