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[QUIC] Stream write cancellation #53304

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Merged
CarnaViire merged 8 commits into from
Jun 4, 2021
Merged

[QUIC] Stream write cancellation #53304

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10d77d2
Add test to check write cancellation behavior and fix mock stream
CarnaViire May 26, 2021
eb17b63
Add throwing on msquic returning write canceled status
CarnaViire May 26, 2021
62895f6
Unify canceled spelling
CarnaViire May 26, 2021
fe84604
Merge remote-tracking branch 'upstream/main' into stream-cancellation
CarnaViire May 27, 2021
2c5f97d
Merge branch 'main' into stream-cancellation
CarnaViire May 27, 2021
d443a76
Fix pre-cancelled writes and add test
CarnaViire Jun 1, 2021
9af76d1
Rewrite cancellation test to be reliable
CarnaViire Jun 2, 2021
b7b2f85
Put timeout on infinite test loop
CarnaViire Jun 3, 2021
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16 changes: 16 additions & 0 deletions src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/Mock/MockStream.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ internal sealed class MockStream : QuicStreamProvider
private readonly bool _isInitiator;

private readonly StreamState _streamState;
private bool _writesCanceled;

internal MockStream(StreamState streamState, bool isInitiator)
{
Expand Down Expand Up @@ -84,6 +85,10 @@ internal override async ValueTask<int> ReadAsync(Memory<byte> buffer, Cancellati
internal override void Write(ReadOnlySpan<byte> buffer)
{
CheckDisposed();
if (Volatile.Read(ref _writesCanceled))
{
throw new OperationCanceledException();
}

StreamBuffer? streamBuffer = WriteStreamBuffer;
if (streamBuffer is null)
Expand All @@ -102,13 +107,24 @@ internal override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, Cancellation
internal override async ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, bool endStream, CancellationToken cancellationToken = default)
{
CheckDisposed();
if (Volatile.Read(ref _writesCanceled))
{
cancellationToken.ThrowIfCancellationRequested();
throw new OperationCanceledException();
}

StreamBuffer? streamBuffer = WriteStreamBuffer;
if (streamBuffer is null)
{
throw new NotSupportedException();
}

using var registration = cancellationToken.UnsafeRegister(static s =>
{
var stream = (MockStream)s!;
Volatile.Write(ref stream._writesCanceled, true);
}, this);

await streamBuffer.WriteAsync(buffer, cancellationToken).ConfigureAwait(false);

if (endStream)
Expand Down
50 changes: 34 additions & 16 deletions src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicStream.cs
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Expand Up @@ -216,18 +216,14 @@ private async ValueTask<CancellationTokenRegistration> HandleWriteStartState(Can
throw new InvalidOperationException(SR.net_quic_writing_notallowed);
}

lock (_state)
// Make sure start has completed
if (!_started)
{
if (_state.SendState == SendState.Aborted)
{
throw new OperationCanceledException(SR.net_quic_sending_aborted);
}
else if (_state.SendState == SendState.ConnectionClosed)
{
throw GetConnectionAbortedException(_state);
}
await _state.SendResettableCompletionSource.GetTypelessValueTask().ConfigureAwait(false);
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@CarnaViire CarnaViire Jun 1, 2021

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If I don't wait for it before creating CancellationTokenRegistration, in case of pre-cancelled token, SendResettableCompletionSource.CompleteException fails with InvalidOperationException: Operation is not valid due to the current state of the object. 🤔

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@ManickaP ManickaP Jun 2, 2021

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Yeah, we guard the ResettableCompletionSource completion with SendState, but it "breaks" here since we're (ab)using SendResettableCompletionSource for START_COMPLETE as well.
I don't have any better suggestions than what you did here.

_started = true;
}

// if token was already cancelled, this would execute syncronously
CancellationTokenRegistration registration = cancellationToken.UnsafeRegister(static (s, token) =>
{
var state = (State)s!;
Expand All @@ -248,11 +244,17 @@ private async ValueTask<CancellationTokenRegistration> HandleWriteStartState(Can
}
}, _state);

// Make sure start has completed
if (!_started)
lock (_state)
{
await _state.SendResettableCompletionSource.GetTypelessValueTask().ConfigureAwait(false);
_started = true;
if (_state.SendState == SendState.Aborted)
{
cancellationToken.ThrowIfCancellationRequested();
throw new OperationCanceledException(SR.net_quic_sending_aborted);
}
else if (_state.SendState == SendState.ConnectionClosed)
{
throw GetConnectionAbortedException(_state);
}
}

return registration;
Expand All @@ -262,7 +264,7 @@ private void HandleWriteCompletedState()
{
lock (_state)
{
if (_state.SendState == SendState.Finished || _state.SendState == SendState.Aborted)
if (_state.SendState == SendState.Finished)
{
_state.SendState = SendState.None;
}
Expand Down Expand Up @@ -827,6 +829,9 @@ private static uint HandleEventPeerSendShutdown(State state)

private static uint HandleEventSendComplete(State state, ref StreamEvent evt)
{
StreamEventDataSendComplete sendCompleteEvent = evt.Data.SendComplete;
bool canceled = sendCompleteEvent.Canceled != 0;

bool complete = false;

lock (state)
Expand All @@ -836,13 +841,26 @@ private static uint HandleEventSendComplete(State state, ref StreamEvent evt)
state.SendState = SendState.Finished;
complete = true;
}

if (canceled)
{
state.SendState = SendState.Aborted;
}
}

if (complete)
{
CleanupSendState(state);
// TODO throw if a write was canceled.
state.SendResettableCompletionSource.Complete(MsQuicStatusCodes.Success);

if (!canceled)
{
state.SendResettableCompletionSource.Complete(MsQuicStatusCodes.Success);
}
else
{
state.SendResettableCompletionSource.CompleteException(
ExceptionDispatchInfo.SetCurrentStackTrace(new OperationCanceledException("Write was canceled")));
}
}

return MsQuicStatusCodes.Success;
Expand Down
133 changes: 133 additions & 0 deletions src/libraries/System.Net.Quic/tests/FunctionalTests/QuicStreamTests.cs
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Expand Up @@ -6,6 +6,7 @@
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Xunit;

Expand Down Expand Up @@ -434,6 +435,138 @@ await Task.Run(async () =>
Assert.Equal(ExpectedErrorCode, ex.ErrorCode);
}).WaitAsync(TimeSpan.FromSeconds(15));
}

[ActiveIssue("https://github.com/dotnet/runtime/issues/53530")]
[Fact]
public async Task StreamAbortedWithoutWriting_ReadThrows()
{
long expectedErrorCode = 1234;

await RunClientServer(
clientFunction: async connection =>
{
await using QuicStream stream = connection.OpenUnidirectionalStream();
stream.AbortWrite(expectedErrorCode);

await stream.ShutdownCompleted();
},
serverFunction: async connection =>
{
await using QuicStream stream = await connection.AcceptStreamAsync();

byte[] buffer = new byte[1];

QuicStreamAbortedException ex = await Assert.ThrowsAsync<QuicStreamAbortedException>(() => ReadAll(stream, buffer));
Assert.Equal(expectedErrorCode, ex.ErrorCode);

await stream.ShutdownCompleted();
}
);
}

[Fact]
public async Task WritePreCanceled_Throws()
{
long expectedErrorCode = 1234;

await RunClientServer(
clientFunction: async connection =>
{
await using QuicStream stream = connection.OpenUnidirectionalStream();

CancellationTokenSource cts = new CancellationTokenSource();
cts.Cancel();
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@CarnaViire CarnaViire May 27, 2021 •
edited
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This way of testing cancellation is not reliable. Sometimes it seems that task finishes before cancellation occurs. Does anyone have an idea on how to make sure write is not over before cancellation? Pre-cancelling before calling WriteAsync is not appealing to me...

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@ManickaP ManickaP May 27, 2021 •
edited
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I can only think of ways which touch MsQuicStream code so no help, sorry.
But I think that adding extra test for pre-cancellation is actually a good idea. I'm looking at the code and it looks like we will send the data even if the token has been cancelled beforehand. Is that expected behavior? Should we do some best-effort token check before we call into msquic? Or did I just overlook something 😊

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@CarnaViire CarnaViire Jun 1, 2021

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Sending 64M instead of 1M helped, at least I didn't get any failures on my setup while running it ~20 times. If someone believes it is not reliable enough, the only option I see here is to remove this test completely. I've added a second one that checks pre-cancelled token.

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@CarnaViire CarnaViire Jun 2, 2021

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Rewrote to an infinite loop until canceled, as per @geoffkizer suggestion

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@ManickaP ManickaP Jun 2, 2021

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Could that infinite loop be somehow finite, but still big enough for the test? I already see hanging tests in CI :)


await Assert.ThrowsAsync<OperationCanceledException>(() => stream.WriteAsync(new byte[1], cts.Token).AsTask());

// next write would also throw
await Assert.ThrowsAsync<OperationCanceledException>(() => stream.WriteAsync(new byte[1]).AsTask());

// manual write abort is still required
stream.AbortWrite(expectedErrorCode);

await stream.ShutdownCompleted();
},
serverFunction: async connection =>
{
await using QuicStream stream = await connection.AcceptStreamAsync();

byte[] buffer = new byte[1024 * 1024];

// TODO: it should always throw QuicStreamAbortedException, but sometimes it does not https://github.com/dotnet/runtime/issues/53530
//QuicStreamAbortedException ex = await Assert.ThrowsAsync<QuicStreamAbortedException>(() => ReadAll(stream, buffer));
try
{
await ReadAll(stream, buffer);
}
catch (QuicStreamAbortedException) { }

await stream.ShutdownCompleted();
}
);
}

[Fact]
public async Task WriteCanceled_NextWriteThrows()
{
long expectedErrorCode = 1234;

await RunClientServer(
clientFunction: async connection =>
{
await using QuicStream stream = connection.OpenUnidirectionalStream();

CancellationTokenSource cts = new CancellationTokenSource(500);

async Task WriteUntilCanceled()
{
var buffer = new byte[64 * 1024];
while (true)
{
await stream.WriteAsync(buffer, cancellationToken: cts.Token);
}
}

// a write would eventually be canceled
await Assert.ThrowsAsync<OperationCanceledException>(() => WriteUntilCanceled().WaitAsync(TimeSpan.FromSeconds(3)));

// next write would also throw
await Assert.ThrowsAsync<OperationCanceledException>(() => stream.WriteAsync(new byte[1]).AsTask());

// manual write abort is still required
stream.AbortWrite(expectedErrorCode);

await stream.ShutdownCompleted();
},
serverFunction: async connection =>
{
await using QuicStream stream = await connection.AcceptStreamAsync();

async Task ReadUntilAborted()
{
var buffer = new byte[1024];
while (true)
{
int res = await stream.ReadAsync(buffer);
if (res == 0)
{
break;
}
}
}

// TODO: it should always throw QuicStreamAbortedException, but sometimes it does not https://github.com/dotnet/runtime/issues/53530
//QuicStreamAbortedException ex = await Assert.ThrowsAsync<QuicStreamAbortedException>(() => ReadUntilAborted());
try
{
await ReadUntilAborted().WaitAsync(TimeSpan.FromSeconds(3));
}
catch (QuicStreamAbortedException) { }

await stream.ShutdownCompleted();
}
);
}
}

public sealed class QuicStreamTests_MockProvider : QuicStreamTests<MockProviderFactory> { }
Expand Down