Have a way to get failure from publish method if mqtt broker not reachable

[martinscheffler]

Hi,
I have a scenario where no message may get lost. It would be good if there was a way to call publish and have it fail if it cannot be delivered immediately.

[frederikaalund]

Hi Martin

Thanks for opening this discussion.

I have a scenario where no message may get lost.

Sounds like a good fit for QoS level 1 and above.

It would be good if there was a way to call publish and have it fail if it cannot be delivered immediately.

When await client.publish(topic, message, qos=1) returns, the message is at the broker (all send/receive/handshaking is done). That's a guarantee from asyncio-mqtt (for QoS level 1 and above). 👍

From there on, it's the broker's responsibility to send the message to the clients. There is nothing asyncio-mqtt can guarantee about that. It's up to the broker.

If asyncio-mqtt can't publish the message, then await client.publish(topic, message, qos=1) raises an exception. The default timeout is 10 seconds and you can change it with the timeout keyword argument.

Does this fit your use case?

~Frederik