Look closer at MQTT buffering

[emiltin]

No description provided.

[emiltin]

How to we deal with a situation where the device looses connection to the broker for prolonged period of time?

[RazeAntoine]

Important messages should be stored so that they can be replayed. Perhaps we should use file storage on site? But it might also be interesting to manage a retention time or an expiry date per type of message, because sometimes certain commands are no longer of interest after a certain time.

[emiltin]

Some MQTT libraries have buffering build-in, but it depends.
For example, I asked about how the Erlang emqtt library handles it at emqx/emqtt#236.
It buffer messages locally in RAM, depending on the Quality of Service, and other factors.

[emiltin]

If we have a good way to fetch historic data, status update might not need to be buffered. Consumers can instead choose when to fetch any missing data. But it assumes that consumers have a way to know when they are missing data.