dht22_exporter

A Prometheus exporter for DHT22 temperature and humidity sensors on Raspberry Pi and GPIO-capable Linux systems.

Reads DHT22 sensors connected to GPIO pins and exposes temperature, humidity, and read-statistics metrics via an HTTP endpoint for Prometheus to scrape.

Features

• Support for multiple DHT22 probes on different GPIO pins
• Statistical filtering of readings (outlier removal via standard deviation bounds)
• Automatic retry on transient sensor errors
• Configurable read intervals, sample sizes, and tolerance thresholds

Requirements

• Python 3.9+
• Raspberry Pi or Linux system with GPIO support
• DHT22 sensor(s) wired to GPIO pins

Installation

pip install dht22-exporter

Or with Poetry:

poetry install

Configuration

Create a JSON configuration file at /etc/dht22_exporter.json or ~/.config/dht22_exporter.json:

{
  "name": "dht22-exporter",
  "sleep_between_read": 1,
  "max_ping_read_retry": 3,
  "temp_tolerated_stdev": 1,
  "humidity_tolerated_stdev": 2,
  "probes": [
    {
      "gpio_pin": 4,
      "name": "bedroom",
      "probe_type": "room",
      "location": "upstairs"
    },
    {
      "gpio_pin": 17,
      "name": "outside",
      "probe_type": "outside",
      "location": "north-wall"
    }
  ],
  "loop": {
    "interval": 240
  },
  "prometheus": {
    "port": 9100,
    "namespace": ""
  },
  "logging": {
    "level": "WARNING"
  }
}

Configuration reference

Parameter	Default	Description
sleep_between_read	1	Seconds between consecutive sensor reads
max_ping_read_retry	3	Max retries on transient sensor errors
temp_tolerated_stdev	1	Temperature std-dev tolerance (°C)
humidity_tolerated_stdev	2	Humidity std-dev tolerance (%)
loop.interval	240	Seconds between collection cycles
prometheus.port	9100	HTTP port for the metrics endpoint
prometheus.namespace	""	Prometheus metric namespace prefix
logging.level	"WARNING"	Log level (DEBUG, INFO, WARNING, ERROR, FATAL)

Each probe entry requires gpio_pin (int), name (str), probe_type (str), and location (str).

Usage

python dht22_exporter.py

Metrics are then available at http://<host>:9100/metrics.

Metrics

temps (Gauge)

Temperature in degrees Celsius.

Labels: name, type, location, probe, serial

humidity (Gauge)

Relative humidity in percent.

Labels: name, type, location, probe, serial

probe_read (Counter)

I/O statistics for sensor reads.

Labels: name, type, location, probe, serial, result

Result values: ok (successful read), ko (failed read), used (reading included in final measurement), ignored (reading filtered as outlier).

How it works

Each collection cycle (default 240 s):

1. Collects 5 temperature/humidity samples per probe, sleeping 1 s between reads.
2. Retries transient read failures up to max_ping_read_retry times.
3. Removes outliers that exceed the configured standard deviation thresholds.
4. Requires at least 3 valid samples to accept a reading.
5. Reports the mean of the remaining samples, rounded to 2 decimal places.

Development

make lint      # run all linters (pep8, black, pylint, mypy)
make build     # clean, lint, and build
make publish   # build and publish to PyPI