DeviceClient.ReceiveAsync ignores token cancellation

[dkattan]

Context

• .NET 5
• DeviceClient SDK 1.36
• AMQP

Description of the issue

DeviceClient.ReceiveAsync(CancellationToken cancellationToken) method does not exit when cancellationToken is cancelled.

The current tests simply verify that the task returns immediately when passed a cancellationToken that is already cancelled.

Code sample exhibiting the issue

protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
      stoppingToken.Register(() => { _logger.LogInformation("Stopping Token Called"); });
      while (!stoppingToken.IsCancellationRequested)
      {
        using Message receivedMessage = await DeviceClient.ReceiveAsync(stoppingToken);
        if (receivedMessage == null) continue;
      }
     _logger.LogInformation(“Exiting Application”);
}

Console log of the issue

Stopping Token Called

Expected Result

Stopping Token Called
Exiting Application

Workaround

To workaround this I have changed my code to use the ReceiveAsync(TimeSpan) overload, but it feels hacky.

[timtay-microsoft]

Looks like the SDK uses the default receive timeout set in the transport settings rather than the cancellation token when using the receiveAsync API.

azure-iot-sdk-csharp/iothub/device/src/Transport/Amqp/AmqpTransportHandler.cs

Line 206 in 118a15e

message = await _amqpUnit.ReceiveMessageAsync(_transportSettings.DefaultReceiveTimeout).ConfigureAwait(false);

That seems like a bug to me as well, so I'll fix this

[timtay-microsoft]

After further investigation, the real issue here appears to be that the AMQP library we use simply doesn't accept cancellation tokens. Instead, it only accepts TimeSpans as you can see here. I'll discuss this a bit more with my team.

[timtay-microsoft]

Looks like there is already an ask out for adding support for cancellation tokens to the AMQP library in question here. Ideally they would add support and we could just pass along the cancellation token as expected.