[mosquitto-dev] Info about V5 implementation ?

[Carlos G Mendioroz <tron@xxxxxxx>]

Hi,
I'm running a mosquitto broker, using v3.1.1 I guess, by default.
So far it has been great, some issues with some client libraries
handling reconnection issues but nothing terribly bad.

I have implemented (or I'm in the  process of) prometheus and a bridge
to store topics history for analysis, graphing and alarms. And in the
process I came to miss the possibility of forgetting: my sensors send
e.g. a temperature reading to the broker with retain bit set, so clients
can pull "current" temperature at will, but if a sensor goes belly up,
then the bridge (implemented with prometheus python client) and the
broker (via persistence) keep the last temp "alive".

MQTT v5 seems a perfect fit to have a TTL value for measurements. 60
minutes old temp has no longer value as actual state. In fact, it makes
a lot easier to trigger alarms when is self evident that a sensor is not
alive. (I'm generating virtual alive data by a phantom topic with
timestamp for the time being).

So when looking at v5 I have been unable to find documentation that
shows things like:
-can I run -V 5 and still connect via 3.1.1 clients ?
-can I have different listeners for different protocols ?
-is there a way to migrate without "D" day ?

I decided to post here after finding that the main page at
https://mosquitto.org/man/mosquitto-8.html and many others still cite
mosquitto as a 3.1/3.1.1 version broker, even though release 1.6 says
there is v5 support.

TIA,
-Carlos

-- 
Carlos G Mendioroz  <tron@xxxxxxx>