[MQTT] Availability Topic not working?

[eikowagenknecht]

@rlkoshak

Before going too far along, I must mention that there is a Shelly binding that does not require MQTT which should be far simpler to set up and use.

That would indeed be a simpler approach and I did not see that there was a binding specifically for the Shellys. So thank you for that hint. But since I stumbled upon MQTT related things quite often recently I thougt this would be a good reason to more deeply understand how MQTT works. And after some reading, I think I got most of it. So now it’s time for practice

@rlkoshak

I don’t know whether or not that availability topic is supposed to control the ONLINE/OFFLINE status of the Thing. It could be used to update the Items linked to that Thing’s Channels to UNDEF when it goes offline only.

That would be possible, but the Items linked to this Thing’s Channels do exactly nothing, e.g do not change to UNDEF either.

I just found an older post referring to this Github issue saying it was actually broken for HomeAssistant Things (I’m using Generic MQTT Thing instead), but this could quite probably be related. Also that post and issue seems to confirm my understanding of the intention this setting has - Device offline (e.g. battery empty) → Thing OFFLINE in openHAB, even though the connection is still available through the MQTT broker and a potentially retained message.