Add Retain Message Flag

[mkyral]

I'm testing bigclown sensors with homeassistant (hass) on Turris 1.1 and it doesn't work well. Hass connects to mqtt broker periodically and in many times it simply miss the value change from sensor.

After some searching I've found that there is "Retain Message Flag", that tells broker to store the last value. So hass always gets the last value when asks.

I've tested it, extended the publish function call with parameter retain=True and now hass works as I expect.

So it will be nice to have this flag in configuration and I can enable it when need.

Only question I have: is it OK to enable it for all published messages in general or should be configurable per message type or even per message?

[jirutka]

It makes sense to use retain messages for some topics, but definitely not for all (in general) - it'd be incorrect solution for this issue. MQTT supports persistent sessions.

[mkyral]

Thanks for info. I have to test it, but it looks like setting mqtt client_id in homeassistant configuration should be enough.

https://home-assistant.io/docs/mqtt/broker/#run-your-own

[blavka]

Its good idea, added to config, list for topics with retain flag.
I'll definitely add it in the near future.