Fix capturing ExecutionContext by timers and background tasks (#2129)

Author: JamesNK

global.json

@@ -1,5 +1,6 @@
 {
   "sdk": {
-    "version": "7.0.201"
+    "version": "7.0.201",
+    "rollForward": "latestFeature"
   }
 }

src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj

@@ -30,6 +30,7 @@
     <Compile Include="..\Shared\Server\UnaryServerMethodInvoker.cs" Link="Model\Internal\UnaryServerMethodInvoker.cs" />
     <Compile Include="..\Shared\NullableAttributes.cs" Link="Internal\NullableAttributes.cs" />
     <Compile Include="..\Shared\CodeAnalysisAttributes.cs" Link="Internal\CodeAnalysisAttributes.cs" />
+    <Compile Include="..\Shared\NonCapturingTimer.cs" Link="Internal\NonCapturingTimer.cs" />
   </ItemGroup>
 
   <ItemGroup>

src/Grpc.AspNetCore.Server/Internal/ServerCallDeadlineManager.cs

@@ -1,4 +1,4 @@
-#region Copyright notice and license
+#region Copyright notice and license
 
 // Copyright 2019 The gRPC Authors
 //
@@ -91,12 +91,12 @@ public ServerCallDeadlineManager(HttpContextServerCallContext serverCallContext,
             // Ensures there is no weird situation where the timer triggers
             // before the field is set. Shouldn't happen because only long deadlines
             // will take this path but better to be safe than sorry.
-            _longDeadlineTimer = new Timer(DeadlineExceededLongDelegate, (this, maxTimerDueTime), Timeout.Infinite, Timeout.Infinite);
+            _longDeadlineTimer = NonCapturingTimer.Create(DeadlineExceededLongDelegate, (this, maxTimerDueTime), Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);
             _longDeadlineTimer.Change(timerMilliseconds, Timeout.Infinite);
         }
         else
         {
-            _longDeadlineTimer = new Timer(DeadlineExceededDelegate, this, timerMilliseconds, Timeout.Infinite);
+            _longDeadlineTimer = NonCapturingTimer.Create(DeadlineExceededDelegate, this, TimeSpan.FromMilliseconds(timerMilliseconds), Timeout.InfiniteTimeSpan);
         }
     }
 

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

@@ -68,7 +68,7 @@ protected override void OnStarted()
 
         if (_refreshInterval != Timeout.InfiniteTimeSpan)
         {
-            _timer = new Timer(OnTimerCallback, null, Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);
+            _timer = NonCapturingTimer.Create(OnTimerCallback, state: null, Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);
             _timer.Change(_refreshInterval, _refreshInterval);
         }
     }

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

@@ -1,4 +1,4 @@
-#region Copyright notice and license
+#region Copyright notice and license
 
 // Copyright 2019 The gRPC Authors
 //
@@ -77,7 +77,7 @@ public SocketConnectivitySubchannelTransport(
         ConnectTimeout = connectTimeout;
         _socketConnect = socketConnect ?? OnConnect;
         _activeStreams = new List<ActiveStream>();
-        _socketConnectedTimer = new Timer(OnCheckSocketConnection, state: null, Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);
+        _socketConnectedTimer = NonCapturingTimer.Create(OnCheckSocketConnection, state: null, Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);
     }
 
     private object Lock => _subchannel.Lock;

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

@@ -1,4 +1,4 @@
-#region Copyright notice and license
+#region Copyright notice and license
 
 // Copyright 2019 The gRPC Authors
 //
@@ -86,7 +86,7 @@ protected PollingResolver(ILoggerFactory loggerFactory, IBackoffPolicyFactory? b
     /// </para>
     /// </summary>
     /// <param name="listener">The callback used to receive updates on the target.</param>
-    public override sealed void Start(Action<ResolverResult> listener)
+    public sealed override void Start(Action<ResolverResult> listener)
     {
         if (listener == null)
         {

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

@@ -1,4 +1,4 @@
-#region Copyright notice and license
+#region Copyright notice and license
 
 // Copyright 2019 The gRPC Authors
 //
@@ -233,7 +233,21 @@ public void RequestConnection()
             }
         }
 
-        _ = ConnectTransportAsync();
+        // Don't capture the current ExecutionContext and its AsyncLocals onto the connect
+        bool restoreFlow = false;
+        if (!ExecutionContext.IsFlowSuppressed())
+        {
+            ExecutionContext.SuppressFlow();
+            restoreFlow = true;
+        }
+
+        _ = Task.Run(ConnectTransportAsync);
+
+        // Restore the current ExecutionContext
+        if (restoreFlow)
+        {
+            ExecutionContext.RestoreFlow();
+        }
     }
 
     private void CancelInProgressConnect()

src/Grpc.Net.Client/Grpc.Net.Client.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <Description>.NET client for gRPC</Description>
@@ -35,6 +35,7 @@
     <Compile Include="..\Shared\NullableAttributes.cs" Link="Internal\NullableAttributes.cs" />
     <Compile Include="..\Shared\Http2ErrorCode.cs" Link="Internal\Http2ErrorCode.cs" />
     <Compile Include="..\Shared\Http3ErrorCode.cs" Link="Internal\Http3ErrorCode.cs" />
+    <Compile Include="..\Shared\NonCapturingTimer.cs" Link="Internal\NonCapturingTimer.cs" />
     <Compile Include="..\Shared\NonDisposableMemoryStream.cs" Link="Internal\NonDisposableMemoryStream.cs" />
   </ItemGroup>
 

src/Grpc.Net.Client/GrpcChannel.cs

@@ -54,8 +54,7 @@ public sealed class GrpcChannel : ChannelBase, IDisposable
     private readonly Dictionary<MethodKey, MethodConfig>? _serviceConfigMethods;
     private readonly bool _isSecure;
     private readonly List<CallCredentials>? _callCredentials;
-    // Internal for testing
-    internal readonly HashSet<IDisposable> ActiveCalls;
+    private readonly HashSet<IDisposable> _activeCalls;
 
     internal Uri Address { get; }
     internal HttpMessageInvoker HttpInvoker { get; }
@@ -165,7 +164,7 @@ internal GrpcChannel(Uri address, GrpcChannelOptions channelOptions) : base(addr
         ThrowOperationCanceledOnCancellation = channelOptions.ThrowOperationCanceledOnCancellation;
         UnsafeUseInsecureChannelCallCredentials = channelOptions.UnsafeUseInsecureChannelCallCredentials;
         _createMethodInfoFunc = CreateMethodInfo;
-        ActiveCalls = new HashSet<IDisposable>();
+        _activeCalls = new HashSet<IDisposable>();
         if (channelOptions.ServiceConfig is { } serviceConfig)
         {
             RetryThrottling = serviceConfig.RetryThrottling != null ? CreateChannelRetryThrottling(serviceConfig.RetryThrottling) : null;
@@ -490,15 +489,15 @@ internal void RegisterActiveCall(IDisposable grpcCall)
                 throw new ObjectDisposedException(nameof(GrpcChannel));
             }
 
-            ActiveCalls.Add(grpcCall);
+            _activeCalls.Add(grpcCall);
         }
     }
 
     internal void FinishActiveCall(IDisposable grpcCall)
     {
         lock (_lock)
         {
-            ActiveCalls.Remove(grpcCall);
+            _activeCalls.Remove(grpcCall);
         }
     }
 
@@ -749,9 +748,9 @@ public void Dispose()
                 return;
             }
 
-            if (ActiveCalls.Count > 0)
+            if (_activeCalls.Count > 0)
             {
-                activeCallsCopy = ActiveCalls.ToArray();
+                activeCallsCopy = _activeCalls.ToArray();
             }
 
             Disposed = true;
@@ -807,6 +806,15 @@ internal int GetRandomNumber(int minValue, int maxValue)
         }
     }
 
+    // Internal for testing
+    internal IDisposable[] GetActiveCalls()
+    {
+        lock (_lock)
+        {
+            return _activeCalls.ToArray();
+        }
+    }
+
 #if SUPPORT_LOAD_BALANCING
     private sealed class SubChannelTransportFactory : ISubchannelTransportFactory
     {

src/Grpc.Net.Client/Internal/GrpcCall.cs

@@ -838,7 +838,7 @@ public Exception CreateFailureStatusException(Status status)
                 GrpcCallLog.StartingDeadlineTimeout(Logger, timeout.Value);
 
                 var dueTime = CommonGrpcProtocolHelpers.GetTimerDueTime(timeout.Value, Channel.MaxTimerDueTime);
-                _deadlineTimer = new Timer(DeadlineExceededCallback, null, dueTime, Timeout.Infinite);
+                _deadlineTimer = NonCapturingTimer.Create(DeadlineExceededCallback, state: null, TimeSpan.FromMilliseconds(dueTime), Timeout.InfiniteTimeSpan);
             }
         }