handle failures in async call initialization without leaks

src/csharp/Grpc.Core.Tests/Internal/AsyncCallTest.cs

@@ -106,6 +106,24 @@ namespace Grpc.Core.Internal.Tests
             AssertUnaryResponseError(asyncCall, fakeCall, resultTask, StatusCode.Internal);
         }
 
+        [Test]
+        public void AsyncUnary_RequestSerializationExceptionDoesntLeakResources()
+        {
+            string nullRequest = null;  // will throw when serializing
+            Assert.Throws(typeof(ArgumentNullException), () => asyncCall.UnaryCallAsync(nullRequest));
+            Assert.AreEqual(0, channel.GetCallReferenceCount());
+            Assert.IsTrue(fakeCall.IsDisposed);
+        }
+
+        [Test]
+        public void AsyncUnary_StartCallFailureDoesntLeakResources()
+        {
+            fakeCall.MakeStartCallFail();
+            Assert.Throws(typeof(InvalidOperationException), () => asyncCall.UnaryCallAsync("request1"));
+            Assert.AreEqual(0, channel.GetCallReferenceCount());
+            Assert.IsTrue(fakeCall.IsDisposed);
+        }
+
         [Test]
         public void ClientStreaming_StreamingReadNotAllowed()
         {
@@ -327,6 +345,15 @@ namespace Grpc.Core.Internal.Tests
             AssertUnaryResponseError(asyncCall, fakeCall, resultTask, StatusCode.Cancelled);
         }
 
+        [Test]
+        public void ClientStreaming_StartCallFailureDoesntLeakResources()
+        {
+            fakeCall.MakeStartCallFail();
+            Assert.Throws(typeof(InvalidOperationException), () => asyncCall.ClientStreamingCallAsync());
+            Assert.AreEqual(0, channel.GetCallReferenceCount());
+            Assert.IsTrue(fakeCall.IsDisposed);
+        }
+
         [Test]
         public void ServerStreaming_StreamingSendNotAllowed()
         {
@@ -401,6 +428,27 @@ namespace Grpc.Core.Internal.Tests
             AssertStreamingResponseSuccess(asyncCall, fakeCall, readTask3);
         }
 
+        [Test]
+        public void ServerStreaming_RequestSerializationExceptionDoesntLeakResources()
+        {
+            string nullRequest = null;  // will throw when serializing
+            Assert.Throws(typeof(ArgumentNullException), () => asyncCall.StartServerStreamingCall(nullRequest));
+            Assert.AreEqual(0, channel.GetCallReferenceCount());
+            Assert.IsTrue(fakeCall.IsDisposed);
+
+            var responseStream = new ClientResponseStream<string, string>(asyncCall);
+            var readTask = responseStream.MoveNext();
+        }
+
+        [Test]
+        public void ServerStreaming_StartCallFailureDoesntLeakResources()
+        {
+            fakeCall.MakeStartCallFail();
+            Assert.Throws(typeof(InvalidOperationException), () => asyncCall.StartServerStreamingCall("request1"));
+            Assert.AreEqual(0, channel.GetCallReferenceCount());
+            Assert.IsTrue(fakeCall.IsDisposed);
+        }
+
         [Test]
         public void DuplexStreaming_NoRequestNoResponse_Success()
         {
@@ -558,6 +606,15 @@ namespace Grpc.Core.Internal.Tests
             AssertStreamingResponseError(asyncCall, fakeCall, readTask2, StatusCode.Cancelled);
         }
 
+        [Test]
+        public void DuplexStreaming_StartCallFailureDoesntLeakResources()
+        {
+            fakeCall.MakeStartCallFail();
+            Assert.Throws(typeof(InvalidOperationException), () => asyncCall.StartDuplexStreamingCall());
+            Assert.AreEqual(0, channel.GetCallReferenceCount());
+            Assert.IsTrue(fakeCall.IsDisposed);
+        }
+
         ClientSideStatus CreateClientSideStatus(StatusCode statusCode)
         {
             return new ClientSideStatus(new Status(statusCode, ""), new Metadata());

src/csharp/Grpc.Core.Tests/Internal/FakeNativeCall.cs

@@ -31,6 +31,7 @@ namespace Grpc.Core.Internal.Tests
     /// </summary>
     internal class FakeNativeCall : INativeCall
     {
+        private bool shouldStartCallFail;
         public IUnaryResponseClientCallback UnaryResponseClientCallback
         {
             get;
@@ -102,6 +103,7 @@ namespace Grpc.Core.Internal.Tests
 
         public void StartUnary(IUnaryResponseClientCallback callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
+            StartCallMaybeFail();
             UnaryResponseClientCallback = callback;
         }
 
@@ -112,16 +114,19 @@ namespace Grpc.Core.Internal.Tests
 
         public void StartClientStreaming(IUnaryResponseClientCallback callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
+            StartCallMaybeFail();
             UnaryResponseClientCallback = callback;
         }
 
         public void StartServerStreaming(IReceivedStatusOnClientCallback callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
+            StartCallMaybeFail();
             ReceivedStatusOnClientCallback = callback;
         }
 
         public void StartDuplexStreaming(IReceivedStatusOnClientCallback callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
+            StartCallMaybeFail();
             ReceivedStatusOnClientCallback = callback;
         }
 
@@ -165,5 +170,22 @@ namespace Grpc.Core.Internal.Tests
         {
             IsDisposed = true;
         }
+
+        /// <summary>
+        /// Emulate CallSafeHandle.CheckOk() failure for all future attempts
+        /// to start a call.
+        /// </summary>
+        public void MakeStartCallFail()
+        {
+            shouldStartCallFail = true;
+        }
+
+        private void StartCallMaybeFail()
+        {
+            if (shouldStartCallFail)
+            {
+                throw new InvalidOperationException("Start call has failed.");
+            }
+        }
     }
 }

src/csharp/Grpc.Core/Channel.cs

@@ -297,6 +297,12 @@ namespace Grpc.Core
             activeCallCounter.Decrement();
         }
 
+        // for testing only
+        internal long GetCallReferenceCount()
+        {
+            return activeCallCounter.Count;
+        }
+
         private ChannelState GetConnectivityState(bool tryToConnect)
         {
             try

src/csharp/Grpc.Core/Internal/AsyncCall.cs

@@ -17,6 +17,7 @@
 #endregion
 
 using System;
+using System.Threading;
 using System.Threading.Tasks;
 using Grpc.Core.Logging;
 using Grpc.Core.Profiling;
@@ -34,6 +35,8 @@ namespace Grpc.Core.Internal
         readonly CallInvocationDetails<TRequest, TResponse> details;
         readonly INativeCall injectedNativeCall;  // for testing
 
+        bool registeredWithChannel;
+
         // Dispose of to de-register cancellation token registration
         IDisposable cancellationTokenRegistration;
 
@@ -79,6 +82,9 @@ namespace Grpc.Core.Internal
             {
                 byte[] payload = UnsafeSerialize(msg);
 
+                bool callStartedOk = false;
+                try
+                {
                     unaryResponseTcs = new TaskCompletionSource<TResponse>();
 
                     lock (myLock)
@@ -97,6 +103,8 @@ namespace Grpc.Core.Internal
                         try
                         {
                             call.StartUnary(ctx, payload, GetWriteFlagsForCall(), metadataArray, details.Options.Flags);
+                            callStartedOk = true;
+
                             var ev = cq.Pluck(ctx.Handle);
                             bool success = (ev.success != 0);
                             try
@@ -116,6 +124,18 @@ namespace Grpc.Core.Internal
                             ctx.Recycle();
                         }
                     }
+                }
+                catch (Exception)
+                {
+                    if (!callStartedOk)
+                    {
+                        lock (myLock)
+                        {
+                            OnFailedToStartCallLocked();
+                        }
+                    }
+                    throw;
+                }
                     
                 // Once the blocking call returns, the result should be available synchronously.
                 // Note that GetAwaiter().GetResult() doesn't wrap exceptions in AggregateException.
@@ -129,6 +149,9 @@ namespace Grpc.Core.Internal
         public Task<TResponse> UnaryCallAsync(TRequest msg)
         {
             lock (myLock)
+            {
+                bool callStartedOk = false;
+                try
                 {
                     GrpcPreconditions.CheckState(!started);
                     started = true;
@@ -144,9 +167,20 @@ namespace Grpc.Core.Internal
                     using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                     {
                         call.StartUnary(UnaryResponseClientCallback, payload, GetWriteFlagsForCall(), metadataArray, details.Options.Flags);
+                        callStartedOk = true;
                     }
+
                     return unaryResponseTcs.Task;
                 }
+                catch (Exception)
+                {
+                    if (!callStartedOk)
+                    {
+                        OnFailedToStartCallLocked();
+                    }
+                    throw;
+                }
+            }
         }
 
         /// <summary>
@@ -156,6 +190,9 @@ namespace Grpc.Core.Internal
         public Task<TResponse> ClientStreamingCallAsync()
         {
             lock (myLock)
+            {
+                bool callStartedOk = false;
+                try
                 {
                     GrpcPreconditions.CheckState(!started);
                     started = true;
@@ -168,10 +205,20 @@ namespace Grpc.Core.Internal
                     using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                     {
                         call.StartClientStreaming(UnaryResponseClientCallback, metadataArray, details.Options.Flags);
+                        callStartedOk = true;
                     }
 
                     return unaryResponseTcs.Task;
                 }
+                catch (Exception)
+                {
+                    if (!callStartedOk)
+                    {
+                        OnFailedToStartCallLocked();
+                    }
+                    throw;
+                }
+            }
         }
 
         /// <summary>
@@ -180,6 +227,9 @@ namespace Grpc.Core.Internal
         public void StartServerStreamingCall(TRequest msg)
         {
             lock (myLock)
+            {
+                bool callStartedOk = false;
+                try
                 {
                     GrpcPreconditions.CheckState(!started);
                     started = true;
@@ -194,9 +244,19 @@ namespace Grpc.Core.Internal
                     using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                     {
                         call.StartServerStreaming(ReceivedStatusOnClientCallback, payload, GetWriteFlagsForCall(), metadataArray, details.Options.Flags);
+                        callStartedOk = true;
                     }
                     call.StartReceiveInitialMetadata(ReceivedResponseHeadersCallback);
                 }
+                catch (Exception)
+                {
+                    if (!callStartedOk)
+                    {
+                        OnFailedToStartCallLocked();
+                    }
+                    throw;
+                }
+            }
         }
 
         /// <summary>
@@ -206,6 +266,9 @@ namespace Grpc.Core.Internal
         public void StartDuplexStreamingCall()
         {
             lock (myLock)
+            {
+                bool callStartedOk = false;
+                try
                 {
                     GrpcPreconditions.CheckState(!started);
                     started = true;
@@ -216,9 +279,19 @@ namespace Grpc.Core.Internal
                     using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                     {
                         call.StartDuplexStreaming(ReceivedStatusOnClientCallback, metadataArray, details.Options.Flags);
+                        callStartedOk = true;
                     }
                     call.StartReceiveInitialMetadata(ReceivedResponseHeadersCallback);
                 }
+                catch (Exception)
+                {
+                    if (!callStartedOk)
+                    {
+                        OnFailedToStartCallLocked();
+                    }
+                    throw;
+                }
+            }
         }
 
         /// <summary>
@@ -326,8 +399,12 @@ namespace Grpc.Core.Internal
         }
 
         protected override void OnAfterReleaseResourcesLocked()
+        {
+            if (registeredWithChannel)
             {
                 details.Channel.RemoveCallReference(this);
+                registeredWithChannel = false;
+            }
         }
 
         protected override void OnAfterReleaseResourcesUnlocked()
@@ -394,10 +471,27 @@ namespace Grpc.Core.Internal
             var call = CreateNativeCall(cq);
 
             details.Channel.AddCallReference(this);
+            registeredWithChannel = true;
             InitializeInternal(call);
+
             RegisterCancellationCallback();
         }
 
+        private void OnFailedToStartCallLocked()
+        {
+            ReleaseResources();
+
+            // We need to execute the hook that disposes the cancellation token
+            // registration, but it cannot be done from under a lock.
+            // To make things simple, we just schedule the unregistering
+            // on a threadpool.
+            // - Once the native call is disposed, the Cancel() calls are ignored anyway
+            // - We don't care about the overhead as OnFailedToStartCallLocked() only happens
+            //   when something goes very bad when initializing a call and that should
+            //   never happen when gRPC is used correctly.
+            ThreadPool.QueueUserWorkItem((state) => OnAfterReleaseResourcesUnlocked());
+        }
+
         private INativeCall CreateNativeCall(CompletionQueueSafeHandle cq)
         {
             if (injectedNativeCall != null)

src/csharp/Grpc.Core/Internal/AsyncCallBase.cs

@@ -189,7 +189,7 @@ namespace Grpc.Core.Internal
         /// </summary>
         protected abstract Exception GetRpcExceptionClientOnly();
 
-        private void ReleaseResources()
+        protected void ReleaseResources()
         {
             if (call != null)
             {