I had been contemplating a couple of times, how other users address the issue of "visualising long term trends.". I kind of have even difficulty to properly describe what I am looking for as trending, logging and archiving seem to have different meaning to different people.
My background is in PLC programming (Siemens to be precise) and one of the main functions would be to visualise values over a longer time (days, weeks, months and even years) in graphs with respective values shown as curves. This could be for the purpose to assess certain process conditions in context of other process values, controller optimisation etc.
To do this for my home automation system (e.g. trending of underfloor heating components, including room and outside temperature, along with flow / return flow temperatures and boiler on/off, as well as underfloor heating valves) I am "writing" these values to my homematic CCU (via node-red-contrib-ccu). In turn, homematic has an add-on package called CCU-Historian, which then allows a dynamic creation of charts/graphs of this nature:
So, values get stored in the ccu-historian "database" (really a text file of some sorts), which can be maintained (deleted, compressed, etc. ) over time.
But most importantly, these "survive" any kind of reboot and restart (of course with the exception of the short time, while the system is down). Once you have put together your "graph / curve selection", these can be "recalled" by means of that particular url (values and trend times are stored as a string in the url).
As I am not sure, how much longer I will operate the homematic "in parallel" to my node red RPi, I am always on the lookout for a "simple" replacement of the CCU Historian.
While there is the "ui_chart" function in the dashboard, which is nice for short term trends, I struggle to make any "easy to use" long term trends, which would also survive the above mentioned restart / reboot of the node red RPi.
I am aware that with a "good" logger, there are many moving parts (e.g. database / value maintenance, ui for curve selection / creation, etc.). As I cannot imaged, that I am the "only home enthusiast" with such a requirement, I wanted to find out, how other have done that in their installation!
Looking forward to your input!