Plotting room temperature and humidity using Prometheus, Grafana and a DHT11 sensor

My prometheus server runs in a docker container, which in turn runs in a KVM, which in turn (squared) runs in a physical host I maintain at online.net. I use a VPN to connect all of my hosts and node_exporter is configured to only listen on the VPN interface.

I initially planned on using a cheap NodeMCU/esp8266 board to interface with the sensor and write a simple exporter in the prometheus format. I quickly scraped that idea because I'm using NAT at home and I would either have to do port forwarding or have my router be a part of the VPN and assign IPs in the VPN address space.

I opted for the simpler solution, use a Raspberry Pi and just have it be a client to the VPN. This also meant I got to test DebOps on armv6 based devices.

The implementation was easier than I expected. I run my DebOps-related playbooks, modified some parts to work on armv6, soldered some male pin headers to the raspi and connected the sensor to power/ground and a GPIO pin.

To interface with the sensor, I used a python library by Adafruit and for exporting the metrics I used the official python prometheus client. Nothing fancy here, just hardcoded some glue code and had it run automatically on startup.

from prometheus_client import start_http_server, Gauge
import Adafruit_DHT

t = Gauge('temperature', 'Temperature')
h = Gauge('humidity', 'Humidity')

start_http_server(9222)
while True:
    humidity, temperature = Adafruit_DHT.read_retry(11, 4)
    t.set(temperature)
    h.set(humidity)

Here is a screenshot showcasing the end result plotted in Grafana, where you can clearly see when we turned on/off the AC unit.