[paho-dev] paho-python client PR the java implementation's manualAck

[Peter Silva <peter@xxxxxxxxxxxxxxx>]

Hi folks,

two years ago, I submitted https://github.com/eclipse/paho.mqtt.python/pull/554 to address the issue from 2018: https://github.com/eclipse/paho.mqtt.python/issues/348

The current python library acknowledges receipt of messages (in QoS=1 or 2) before calling the on_message(..) callback, and so leaves a vulnerability where messages may be acknowledged before they are properly received by the application.

The Java implementation behaves the same way by default, but has a manualAck mode boolean flag available to allow the application to take over responsibility should it choose to do so.   There was a lot of discussion around the original PR, so created

this second one to be easier to accept ;-) it literally just brings the functionality existing in the Java implementation as-is to the python one.

I think a lot of people want this feature, it would be great to have it reviewed. 

Thanks.