Advanced use example hangs up about aiomqtt HOT 5 CLOSED

Yes, it is not an issue with the asyncio-mqtt, just in the example code.
Anyway it's handling the exception with your changes :)
So i think you should add that change to README.md

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Anyway it's handling the exception with your changes :)

That's great to hear. I consider this issue solved then. :)

So i think you should add that change to README.md

Already done!

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Thank you for reporting this issue. Let me have a look. :)

You're right, Python's bytes.decode function assumes that the binary represents an UTF8-encoded string per default. If the message.payload (bytes) object does not follow this assumption, decode will raise an exception.

Whether the MQTT message payload is UTF8-encoded text, audio data, video frames, or even empty is completely up to the application (i.e., your usage of MQTT). The asyncio-mqtt does not impose any restrictions here.

In the example code, I have assumed that the message payload is UTF8-encoded text. This was done to make the example code a simple starting point for many applications. In your case, it seems that this assumption led to headaches. Sorry about that.

I can see two options here:

• Add a comment to the example code about the UTF8-encoded text assumption.
• Change the example code to simply display the raw binary data (without the bytes.decode call). The output will be more messy like this but at least it won't make assumptions about the payload.

What do you think? Do you have a third option in mind?

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Thank you for your response.

My point was more about the exception handling.
If any exception will occur in this block of code the code will just hang up.

Regarding the decoding, I think that adding a comment will be enough :)

Right now i implemented this in other way:

async def start_mqtt_client():
    async with Client(
            hostname=config.mqtt.server) as client:

        tasks = []
        tasks.append(asyncio.create_task(handle_bcg(
            client.filtered_messages("/filter1"))))
        tasks.append(asyncio.create_task(handle_sts(
            client.filtered_messages("/filter2"))))

        await client.subscribe("/topic1")
        await client.subscribe("/topic2")
        await asyncio.gather(*tasks)

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Thanks for the follow-up with additional details.

My point was more about the exception handling.
If any exception will occur in this block of code the code will just hang up.

Ah, I see. I could reproduce this behaviour in the advanced example from README.md. I assume that your code is closely based on the advanced example.

I think that is not an issue with asyncio-mqtt itself but with the example code. Specifically, I think that I made a mistake in the cancel_tasks helper function.

Can you please try to apply the following change:

async def cancel_tasks(tasks):
    for task in tasks:
        if task.done():  # Added
            continue     # Added
        task.cancel()
        try:
            await task
        except asyncio.CancelledError:
            pass

Again thanks for reporting this issue. :)

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