digitemp-node-exporter

Scripts & config to get digitemp (DS9097U reading from DS18B20 sensors) into prometheus's node-exporter.

How it works

This defines a systemd timer, which runs every 10 seconds, executing digitemp_DS9097U to collect temperature readings
Output is placed into /var/lib/prometheus/node-exporter/digitemp_DS9097U.prom in the node-exporter's textfile format.
The node-exporter then picks up the output and adds it to the metrics output

The default configuration for prometheus-node-exporter on Debian 9 includes the textfile module automatically and requires no customization for this to work.

Getting started

This has been tested only on Debian 9 (on a Raspberry Pi, any arch will work). The paths may be specific to the Debian prometheus-node-exporter package.

Prerequisites:

Make sure the node-exporter is working. curl http://localhost:9100/metrics
Make sure you have digitemp_DS9097U working already. You should get and output like:

trick@jlh:~/digitemp-node-exporter $ sudo digitemp_DS9097U -c /etc/digitemp.conf -a
DigiTemp v3.7.1 Copyright 1996-2015 by Brian C. Lane
GNU General Public License v2.0 - http://www.digitemp.com
Apr 14 11:27:56 Sensor 0 C: -15.19 F: 4.66
Apr 14 11:27:57 Sensor 1 C: -17.00 F: 1.40

Installation

There isn't a real one yet. I just symlink the files into /etc/systemd/system/. For example:

git clone https://github.com/trickv/digitemp-node-exporter
cd digitemp-node-exporter
find digitemp-node-exporter.* | xargs realpath | xargs -n 1 -I {} sudo ln -s /etc/systemd/system/ {}
sudo systemctl daemon-reload
sudo systemctl enable digitemp-node-exporter.timer
sudo systemctl start digitemp-node-exporter.timer

You can then inspect that the timer is running:

sudo systemctl list-timers digitemp-node-exporter.timer
NEXT                         LEFT    LAST                         PASSED UNIT                         ACTIVATES
Sat 2018-04-14 11:43:00 UTC  1s left Sat 2018-04-14 11:42:55 UTC  3s ago digitemp-node-exporter.timer digitemp-node-exporter.service

...and see the textfile format in place:

trick@jlh:~/digitemp-node-exporter $ sudo cat /var/lib/prometheus/node-exporter/digitemp_DS9097U.prom
digitemp_DS9097U_sensor{address="2854D1BB040000E4"} -14.687500
digitemp_DS9097U_sensor{address="2896ACBA0400001B"} -16.500000

node-exporter output example

In the node-exporter output it should look like this:

trick@jlh:~/digitemp-node-exporter $ curl -s http://localhost:9100/metrics | grep digitemp
# HELP digitemp_DS9097U_sensor Metric read from /var/lib/prometheus/node-exporter/digitemp_DS9097U.prom
# TYPE digitemp_DS9097U_sensor untyped
digitemp_DS9097U_sensor{address="2854D1BB040000E4"} -15.25
digitemp_DS9097U_sensor{address="2896ACBA0400001B"} -17.0625
node_textfile_mtime{file="digitemp_DS9097U.prom"} 1.5237051823351555e+09

To Do

Don't run timer as root
Make a Debian package
Set type of output data
Support other 1-wire sensors? I don't have any other than DS18B20's

Pull requests / forks / taking this work as your own is very welcome. I spent more time writing this readme than I did writing the timer :)