Merge pull request #12822 from jtattermusch/csharp_cancellable_movenext

Add support for CancellationToken in IAsyncStreamReader.MoveNext()

src/csharp/Grpc.Core.Tests/CallCancellationTest.cs

@@ -0,0 +1,182 @@
+#region Copyright notice and license
+
+// Copyright 2015 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Grpc.Core;
+using Grpc.Core.Internal;
+using Grpc.Core.Profiling;
+using Grpc.Core.Utils;
+using NUnit.Framework;
+
+namespace Grpc.Core.Tests
+{
+    public class CallCancellationTest
+    {
+        const string Host = "127.0.0.1";
+
+        MockServiceHelper helper;
+        Server server;
+        Channel channel;
+
+        [SetUp]
+        public void Init()
+        {
+            helper = new MockServiceHelper(Host);
+            server = helper.GetServer();
+            server.Start();
+            channel = helper.GetChannel();
+        }
+
+        [TearDown]
+        public void Cleanup()
+        {
+            channel.ShutdownAsync().Wait();
+            server.ShutdownAsync().Wait();
+        }
+
+        [Test]
+        public async Task ClientStreamingCall_CancelAfterBegin()
+        {
+            var barrier = new TaskCompletionSource<object>();
+
+            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
+            {
+                barrier.SetResult(null);
+                await requestStream.ToListAsync();
+                return "";
+            });
+
+            var cts = new CancellationTokenSource();
+            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall(new CallOptions(cancellationToken: cts.Token)));
+
+            await barrier.Task;  // make sure the handler has started.
+            cts.Cancel();
+
+            try
+            {
+                // cannot use Assert.ThrowsAsync because it uses Task.Wait and would deadlock.
+                await call.ResponseAsync;
+                Assert.Fail();
+            }
+            catch (RpcException ex)
+            {
+                Assert.AreEqual(StatusCode.Cancelled, ex.Status.StatusCode);
+            }
+        }
+
+        [Test]
+        public async Task ClientStreamingCall_ServerSideReadAfterCancelNotificationReturnsNull()
+        {
+            var handlerStartedBarrier = new TaskCompletionSource<object>();
+            var cancelNotificationReceivedBarrier = new TaskCompletionSource<object>();
+            var successTcs = new TaskCompletionSource<string>();
+
+            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
+            {
+                handlerStartedBarrier.SetResult(null);
+
+                // wait for cancellation to be delivered.
+                context.CancellationToken.Register(() => cancelNotificationReceivedBarrier.SetResult(null));
+                await cancelNotificationReceivedBarrier.Task;
+
+                var moveNextResult = await requestStream.MoveNext();
+                successTcs.SetResult(!moveNextResult ? "SUCCESS" : "FAIL");
+                return "";
+            });
+
+            var cts = new CancellationTokenSource();
+            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall(new CallOptions(cancellationToken: cts.Token)));
+
+            await handlerStartedBarrier.Task;
+            cts.Cancel();
+
+            try
+            {
+                await call.ResponseAsync;
+                Assert.Fail();
+            }
+            catch (RpcException ex)
+            {
+                Assert.AreEqual(StatusCode.Cancelled, ex.Status.StatusCode);
+            }
+            Assert.AreEqual("SUCCESS", await successTcs.Task);
+        }
+
+        [Test]
+        public async Task ClientStreamingCall_CancelServerSideRead()
+        {
+            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
+            {
+                var cts = new CancellationTokenSource();
+                var moveNextTask = requestStream.MoveNext(cts.Token);
+                cts.Cancel();
+                await moveNextTask;
+                return "";
+            });
+
+            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall());
+            try
+            {
+                // cannot use Assert.ThrowsAsync because it uses Task.Wait and would deadlock.
+                await call.ResponseAsync;
+                Assert.Fail();
+            }
+            catch (RpcException ex)
+            {
+                Assert.AreEqual(StatusCode.Cancelled, ex.Status.StatusCode);
+            }
+        }
+
+        [Test]
+        public async Task ServerStreamingCall_CancelClientSideRead()
+        {
+            helper.ServerStreamingHandler = new ServerStreamingServerMethod<string, string>(async (request, responseStream, context) =>
+            {
+                await responseStream.WriteAsync("abc");
+                while (!context.CancellationToken.IsCancellationRequested)
+                {
+                    await Task.Delay(10);
+                }
+            });
+
+            var call = Calls.AsyncServerStreamingCall(helper.CreateServerStreamingCall(), "");
+            await call.ResponseStream.MoveNext();
+            Assert.AreEqual("abc", call.ResponseStream.Current);
+
+            var cts = new CancellationTokenSource();
+            var moveNextTask = call.ResponseStream.MoveNext(cts.Token);
+            cts.Cancel();
+
+            try
+            {
+                // cannot use Assert.ThrowsAsync because it uses Task.Wait and would deadlock.
+                await moveNextTask;
+                Assert.Fail();
+            }
+            catch (RpcException ex)
+            {
+                Assert.AreEqual(StatusCode.Cancelled, ex.Status.StatusCode);
+            }
+        }
+    }
+}

src/csharp/Grpc.Core.Tests/ClientServerTest.cs

@@ -272,74 +272,6 @@ namespace Grpc.Core.Tests
             Assert.AreEqual("xyz-value", call.GetTrailers()[0].Value);
         }
 
-        [Test]
-        public async Task ClientStreamingCall_CancelAfterBegin()
-        {
-            var barrier = new TaskCompletionSource<object>();
-
-            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
-            {
-                barrier.SetResult(null);
-                await requestStream.ToListAsync();
-                return "";
-            });
-
-            var cts = new CancellationTokenSource();
-            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall(new CallOptions(cancellationToken: cts.Token)));
-
-            await barrier.Task;  // make sure the handler has started.
-            cts.Cancel();
-
-            try
-            {
-                // cannot use Assert.ThrowsAsync because it uses Task.Wait and would deadlock.
-                await call.ResponseAsync;
-                Assert.Fail();
-            }
-            catch (RpcException ex)
-            {
-                Assert.AreEqual(StatusCode.Cancelled, ex.Status.StatusCode);
-            }
-        }
-
-        [Test]
-        public async Task ClientStreamingCall_ServerSideReadAfterCancelNotificationReturnsNull()
-        {
-            var handlerStartedBarrier = new TaskCompletionSource<object>();
-            var cancelNotificationReceivedBarrier = new TaskCompletionSource<object>();
-            var successTcs = new TaskCompletionSource<string>();
-
-            helper.ClientStreamingHandler = new ClientStreamingServerMethod<string, string>(async (requestStream, context) =>
-            {
-                handlerStartedBarrier.SetResult(null);
-
-                // wait for cancellation to be delivered.
-                context.CancellationToken.Register(() => cancelNotificationReceivedBarrier.SetResult(null));
-                await cancelNotificationReceivedBarrier.Task;
-
-                var moveNextResult = await requestStream.MoveNext();
-                successTcs.SetResult(!moveNextResult ? "SUCCESS" : "FAIL");
-                return "";
-            });
-
-            var cts = new CancellationTokenSource();
-            var call = Calls.AsyncClientStreamingCall(helper.CreateClientStreamingCall(new CallOptions(cancellationToken: cts.Token)));
-
-            await handlerStartedBarrier.Task;
-            cts.Cancel();
-
-            try
-            {
-                await call.ResponseAsync;
-                Assert.Fail();
-            }
-            catch (RpcException ex)
-            {
-                Assert.AreEqual(StatusCode.Cancelled, ex.Status.StatusCode);
-            }
-            Assert.AreEqual("SUCCESS", await successTcs.Task);
-        }
-
         [Test]
         public async Task AsyncUnaryCall_EchoMetadata()
         {

src/csharp/Grpc.Core/IAsyncStreamReader.cs

@@ -41,6 +41,13 @@ namespace Grpc.Core
     /// (<c>MoveNext</c> will return <c>false</c>) and the <c>CancellationToken</c>
     /// associated with the call will be cancelled to signal the failure.
     /// </para>
+    /// <para>
+    /// <c>MoveNext()</c> operations can be cancelled via a cancellation token. Cancelling
+    /// an individual read operation has the same effect as cancelling the entire call
+    /// (which will also result in the read operation returning prematurely), but the per-read cancellation
+    /// tokens passed to MoveNext() only result in cancelling the call if the read operation haven't finished
+    /// yet.
+    /// </para>
     /// </summary>
     /// <typeparam name="T">The message type.</typeparam>
     public interface IAsyncStreamReader<T> : IAsyncEnumerator<T>

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

@@ -49,19 +49,19 @@ namespace Grpc.Core.Internal
 
         public async Task<bool> MoveNext(CancellationToken token)
         {
-            if (token != CancellationToken.None)
+            var cancellationTokenRegistration = token.CanBeCanceled ? token.Register(() => call.Cancel()) : (IDisposable) null;
+            using (cancellationTokenRegistration)
             {
-                throw new InvalidOperationException("Cancellation of individual reads is not supported.");
-            }
-            var result = await call.ReadMessageAsync().ConfigureAwait(false);
-            this.current = result;
+                var result = await call.ReadMessageAsync().ConfigureAwait(false);
+                this.current = result;
 
-            if (result == null)
-            {
-                await call.StreamingResponseCallFinishedTask.ConfigureAwait(false);
-                return false;
+                if (result == null)
+                {
+                    await call.StreamingResponseCallFinishedTask.ConfigureAwait(false);
+                    return false;
+                }
+                return true;
             }
-            return true;
         }
 
         public void Dispose()

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

@@ -49,13 +49,14 @@ namespace Grpc.Core.Internal
 
         public async Task<bool> MoveNext(CancellationToken token)
         {
-            if (token != CancellationToken.None)
+            
+            var cancellationTokenRegistration = token.CanBeCanceled ? token.Register(() => call.Cancel()) : (IDisposable) null;
+            using (cancellationTokenRegistration)
             {
-                throw new InvalidOperationException("Cancellation of individual reads is not supported.");
+                var result = await call.ReadMessageAsync().ConfigureAwait(false);
+                this.current = result;
+                return result != null;
             }
-            var result = await call.ReadMessageAsync().ConfigureAwait(false);
-            this.current = result;
-            return result != null;
         }
 
         public void Dispose()

src/csharp/tests.json

@@ -10,6 +10,7 @@
     "Grpc.Core.Tests.AppDomainUnloadTest",
     "Grpc.Core.Tests.AuthContextTest",
     "Grpc.Core.Tests.AuthPropertyTest",
+    "Grpc.Core.Tests.CallCancellationTest",
     "Grpc.Core.Tests.CallCredentialsTest",
     "Grpc.Core.Tests.CallOptionsTest",
     "Grpc.Core.Tests.ChannelCredentialsTest",