WIP

This project is a work in progress. The implementation is incomplete and subject to change. The documentation can be inaccurate.

Sensor data (RHT03/DHT22 temperature and humidity) in Raspberry Pi 2/3 to the Prometheus open-source monitoring system. It tries to make the sampler as smaller as possible in RAM footprint inside the Raspberry Pi 2/3 since it runs 24x7, so it uses the Adafruit MIT-licensed C-code underlying their Python wrapper:

https://github.com/adafruit/Adafruit_Python_DHT/tree/master/source

Sample output (in Prometheus Text exposition format, https://prometheus.io/docs/instrumenting/exposition_formats/#text-format-details):

      # TYPE dht22_relat_humidity gauge
      # HELP dht22_relat_humidity Relative humidity percentage in the RHT03/DHT22 sensor
      dht22_relat_humidity 22.40 1524280570563
      # TYPE dht22_temperature_celsius gauge
      # HELP dht22_temperature_celsius Temperature in the RHT03/DHT22 sensor
      dht22_temperature_celsius 24.00 1524280570563

To compile this C program:

      make compile

The -h option will give a command-line usage:

      rasppi_dht22_sampler:
      Take samples from a RHT03/DHT22 sensor attached to a Raspberry Pi 2/3 to the Prometheus monitoring system's text collector.

      Optional command-line arguments:
         [-h] [-f] [-g gpio_idx] [-w wait_seconds] [-d directory] [prometheus_label="value"] ...

      Explanation of the optional command-line arguments:

           -h: show these help messages.
           -f: report temperature in Fahrenheit degrees (default: Celsius).
           -g gpio_idx: the GPIO index by which this Raspberry Pi 2/3 communicates with the RHT03/DHT22 (default: 17).
           -w wait_seconds: seconds to wait between consecutive polls from the sensor (default: 60 seconds).
           -d directory: directory where Prometheus' Text-Collector expects the sample metric files to read (default: /var/lib/node_exporter/textfile_collector).
           prometheus_label="value"...: Prometheus label="value" pairs with which to tag the output (default: none).
                                       (Note: Prometheus requires that the value of the label needs to be quoted between '"' double-quotes.
                                        These opening and closing quotes need to be given in the command-line argument.
                                        Probably, in a sh- or bash- like shell, the whole label="value" needs to be protected thus:
                                           'label="value"'.)

The option -d directory for this program must match the option --collector.textfile.directory directory for the Prometheus' node-exporter running in the Raspberry Pi 2/3.

When the -f command-line option is used, the Prometheus metric reported is dht22_temperature_farenheit (and not the default dht22_temperature_celsius, which is how the RHT03/DHT22 originally reports its sample of the temperature).

For example:

      rasppi_dht22_sampler -w 20 -f 'Prometheus_Label_A="1"' 'label_b="2"' 'label_c="3"'

waits 20 seconds between samples, reports the temperature in Farenheit degrees, and labels the metrics with those label-names and values: Prometheus_Label_A="1", label_b="2", and label_c="3":

      # TYPE dht22_relat_humidity gauge
      # HELP dht22_relat_humidity Relative humidity percentage in the RHT03/DHT22 sensor
      dht22_relat_humidity{Prometheus_Label_A="1", label_b="2", label_c="3"} 22.50 1524280806924
      # TYPE dht22_temperature_farenheit gauge
      # HELP dht22_temperature_farenheit Temperature in the RHT03/DHT22 sensor
      dht22_temperature_farenheit{Prometheus_Label_A="1", label_b="2", label_c="3"} 75.38 1524280806924

je-nunez/raspi_sensor_to_prometheus

WIP