Create single MQTT instance at application start-up

[jmrubillon]

I'm not entriely sure how this could be done correctly but maybe using the userdata parameter in the on_connect call could be a mechanism whereby one sets an instance counter when the on_connect callback is triggered and decrements it in the on_disconnect?

Are there any different suggestions? This is just an initial thought after looking at an example in the paho-mqtt repository.

[stlehmann]

@jmrubillon Does this refer to the fact that one can use multiple instances of flask but should not use multiple mqtt clients?

[jmrubillon]

@stlehmann To be quite honest I can't quite remember the context in which I made that particular comment.
I believe it's something to do with multiple instances of Flask should only use the one mqtt client. Now since I can't remember why I made that particular suggestion, I probably had found an alternative way of dealing with it.

[stlehmann]

@jmrubillon Thanks for the feedback. Multiple instances of flask using one single mqtt client would be a nice feature to have. I was thinking about it before but didn't figure out a way to deal with this nicely. I will leave this issue open because maybe someone comes along with a great solution 🤞

[Niraj-Kamdar]

What will be the problem if I use multiple instances of Flask with multiple instances of MQTT client?