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Recipe: from MQTT to InfluxDB via Node-RED

2024-05-16 adds case study explaining how to extract values from topic strings, and how to specify the measurement name in the message payload provided to the "influxdb out" node.
2023-12-02 revise graphics to correspond with "influxdb out" node, and explain the pros and cons of InfluxDB 1.8 vs InfluxDB 2.

Introduction

Getting data produced by IoT sensors into a database is practically a mandatory step before effective visualisation (eg dashboards).

This recipe shows you how to get an MQTT payload into an InfluxDB database using three Node-RED nodes. It makes the following assumptions:

Funny initial commit messages

This is where it all begins...
Commit committed
Version control is awful
COMMIT ALL THE FILES!
The same thing we do every night, Pinky - try to take over the world!
Lock S-foils in attack position
This commit is a lie
I'll explain when you're older!

	#!/bin/bash
	SSH_REDIR_PORT=12345
	SSH_D="cloud_sshd"
	COMMAND="ssh -R $SSH_REDIR_PORT:localhost:22 $SSH_D -N -f"
	pgrep -f "ssh -R $SSH_REDIR_PORT:localhost:22" > /dev/null 2>&1 \|\| (eval $COMMAND && echo $COMMAND)

	#for an image ("not running container") use save:
	docker save <dockernameortag> \| gzip > mycontainer.tgz

	#for running or paused docker, use export:
	docker export <dockernameortag> \| gzip > mycontainer.tgz

	#load
	gunzip -c mycontainer.tgz \| docker load

	#-- coding: utf-8 --
	import subprocess

	if __name__ == '__main__':
	ps = subprocess.Popen(['nodejs','ps2.js'], stdin=subprocess.PIPE, stdout=subprocess.PIPE)

	out = ps.communicate(input='http://www.daum.net'.encode())[0]
	print(out.decode('utf-8'))