Empty message sent when using latest version with HTTP or AMQP about azure-iot-sdk-csharp

[japf]

Update:

After debugging our code with the code of the SDK, I was able to find out the root cause. Before sending the message via SendEventAsync() we log it, and we call the GetBytes() method.

It turns out that calling GetBytes() once prevent the message from being sent properly. What is weird is that if we call GetByes() twice we can an exception but calling GetBytes() and SendEventAsync() fails silently.

I will try to submit a PR if I find a way to improve this behavior.

[japf]

Looks like the source of this problem is in the SendMessageWithRetryAsync method:

async Task SendMessageWithRetryAsync(SendMessageState sendState, Message message, Func<Task> action)
{
    if (sendState.Iteration == 0)
    {
        sendState.InitialStreamPosition = message.BodyStream.CanSeek ? message.BodyStream.Position : UndeterminedPosition;
        message.TryResetBody(sendState.InitialStreamPosition);

        await TryExecuteActionAsync(sendState, action);
        return;
    }

    EnsureStreamIsInOriginalState(sendState, message);

    await TryExecuteActionAsync(sendState, action);
}

Since we called the GetBytes() method before reaching this one, we're going to set the InitialStreamPosition to the end of the stream.

Please let me know if that is clear enough. I also would welcome guidance about how to fix that in the source so that I can propose a PR.

[jasmineymlo]

Hi Japf,
You mentioned that the code works fine with v1.0.11, were you calling GetBytes() to log the message before sending also?
Regards,
Jasmine

[japf]

Yes.

[jasmineymlo]

Hi Japf,
I can repro the issue is v1.0.12 as well and it is fine on v1.0.11. The issue is surfaced due to the fix for taking care of non-seekable stream. Originally, the stream position is hard reset to the beginning before send. Removing the hard reset surfaced the bug in GetBytes()

The proposed fix would be to reset the position in within GetBytes() after reading the stream so that the position would not be altered after the call. I should have the fix ready in next release.

Btw, why are you using GetBytes for logging send messages? You should be able to log using the byte[] which is used for creating the Message object. Thanks.

Regards,
Jasmine

[japf]

I don't have a good reason for using GetBytes() to log the message, the code was just written this way :-)

[jasmineymlo]

Thanks for letting us know about this bug. Here is the commit:
d533f98