Clear IAsyncStreamReader<T>.Current value before reading next value (#…

…2248)

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

@@ -59,6 +59,10 @@ async Task<bool> MoveNextAsync(ValueTask<TRequest?> readStreamTask)
  return Task.FromException<bool>(new InvalidOperationException("Can't read messages after the request is complete."));
  }
 
+ // Clear current before moving next. This prevents rooting the previous value while getting the next one.
+ // In a long running stream this can allow the previous value to be GCed.
+ Current = null!;
+
  var request = _serverCallContext.HttpContext.Request.BodyReader.ReadStreamMessageAsync(_serverCallContext, _deserializer, cancellationToken);
  if (!request.IsCompletedSuccessfully)
  {

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

@@ -156,6 +156,10 @@ private async Task<bool> MoveNextCore(CancellationToken cancellationToken)
 
  CompatibilityHelpers.Assert(_grpcEncoding != null, "Encoding should have been calculated from response.");
 
+ // Clear current before moving next. This prevents rooting the previous value while getting the next one.
+ // In a long running stream this can allow the previous value to be GCed.
+ Current = null!;
+
  var readMessage = await _call.ReadMessageAsync(
  _responseStream,
  _grpcEncoding,

test/Grpc.AspNetCore.Server.Tests/HttpContextStreamReaderTests.cs

@@ -86,4 +86,42 @@ public async Task MoveNext_TokenCancelledDuringMoveNext_CancelTask()
  Assert.AreEqual(1, testSink.Writes.Count);
  Assert.AreEqual("ReadingMessage", testSink.Writes.First().EventId.Name);
  }
+
+ [Test]
+ public async Task MoveNext_MultipleCalls_CurrentClearedBetweenCalls()
+ {
+ // Arrange
+ var ms = new SyncPointMemoryStream();
+
+ var testSink = new TestSink();
+ var testLoggerFactory = new TestLoggerFactory(testSink, enabled: true);
+
+ var httpContext = new DefaultHttpContext();
+ httpContext.Features.Set<IRequestBodyPipeFeature>(new TestRequestBodyPipeFeature(PipeReader.Create(ms)));
+ var serverCallContext = HttpContextServerCallContextHelper.CreateServerCallContext(httpContext, logger: testLoggerFactory.CreateLogger("Test"));
+ var reader = new HttpContextStreamReader<HelloReply>(serverCallContext, MessageHelpers.ServiceMethod.ResponseMarshaller.ContextualDeserializer);
+
+ // Act
+ var nextTask = reader.MoveNext(CancellationToken.None);
+
+ await ms.AddDataAndWait(new byte[]
+ {
+ 0x00, // compression = 0
+ 0x00,
+ 0x00,
+ 0x00,
+ 0x00 // length = 0
+ }).DefaultTimeout();
+
+ Assert.IsTrue(await nextTask.DefaultTimeout());
+ Assert.IsNotNull(reader.Current);
+
+ nextTask = reader.MoveNext(CancellationToken.None);
+
+ Assert.IsFalse(nextTask.IsCompleted);
+ Assert.IsFalse(nextTask.IsCanceled);
+
+ // Assert
+ Assert.IsNull(reader.Current);
+ }
 }

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

@@ -126,6 +126,9 @@ await streamContent.AddDataAndWait(await ClientTestHelpers.GetResponseDataAsync(
  var moveNextTask2 = responseStream.MoveNext(CancellationToken.None);
  Assert.IsFalse(moveNextTask2.IsCompleted);
 
+ // Current is cleared after MoveNext is called.
+ Assert.IsNull(responseStream.Current);
+
  await streamContent.AddDataAndWait(await ClientTestHelpers.GetResponseDataAsync(new HelloReply
  {
  Message = "Hello world 2"