mqtt2rrd
This is the application I use to listen for messages on a MQTT server and feed their values into RRD files.
The config file has a list of matching regular expressions to do the translation between topic and rrd file. The messages should contain only the new value, as they are currently fed directly into rrd without any transformation.
There is a template config file availble in the repository. Usage, then, is like:
$ ./mqtt2rrd.py -v
10:29:48 INFO mqtt2rrd: Connected with result code 0
10:29:48 DEBUG mqtt2rrd: Subscribing to greenhouse/#
10:29:49 WARNING mqtt2rrd: Unmatched: greenhouse/greenery/status b'1'
10:29:49 DEBUG mqtt2rrd: Updated solution_temperature to 16.5625
10:29:49 DEBUG mqtt2rrd: Updated greenhouse_temperature to 21.0
10:29:49 DEBUG mqtt2rrd: Updated greenhouse_humidity to 48.0
10:29:59 WARNING mqtt2rrd: Unmatched: greenhouse/greenery/pump b'0'
10:29:59 DEBUG mqtt2rrd: Updated greenhouse_temperature to 21.0
10:29:59 DEBUG mqtt2rrd: Updated greenhouse_humidity to 48.0
10:30:00 DEBUG mqtt2rrd: Updated solution_temperature to 16.75
10:34:59 DEBUG mqtt2rrd: Updated greenhouse_temperature to 20.0
10:34:59 DEBUG mqtt2rrd: Updated greenhouse_humidity to 49.0
10:35:00 DEBUG mqtt2rrd: Updated solution_temperature to 16.875
10:39:59 DEBUG mqtt2rrd: Updated greenhouse_temperature to 20.0