MQTT2Prometheus

This exporter translates from MQTT topics to prometheus metrics. The core design is that clients send arbitrary JSON messages on the topics. The translation is programmed into the mqtt2prometheus since we often can not change the IoT devices sending the messages. Clients can push metrics via MQTT to an MQTT Broker. This exporter subscribes to the broker and publish the received messages as prometheus metrics. I wrote this exporter to publish metrics from small embedded sensors based on the NodeMCU to prometheus. The used arduino scetch can be found in the dht22tomqtt repository. A local hacking environment with mqtt2prometheus, a MQTT broker and a prometheus server is in the hack directory.

Assumptions about Messages and Topics

This exporter makes some assumptions about the MQTT topics. This exporter assumes that each client publish the metrics into a dedicated topic. The regular expression ìn the configuration field mqtt.device_id_regex defines how to extract the device ID from the MQTT topic. This allow an arbitrary place of the device ID in the mqtt topic. For example the tasmota firmware pushes the telemetry data to the topics tele/<deviceid>/SENSOR.

Let us assume the default configuration from [#ConfigFile]. A sensor publishes the following message

{"temperature":23.20,"humidity":51.60, "computed": {"heat_index":22.92} }

to the MQTT topic devices/me/livingroom. This message becomes the following prometheus metrics:

temperature{sensor="livingroom",topic="devices/me/livingroom"} 23.2
heat_index{sensor="livingroom",topic="devices/me/livingroom"} 22.92
humidity{sensor="livingroom",topic="devices/me/livingroom"} 51.6

Tasmota

An example configuration for the tasmota based Gosund SP111 device is given in examples/gosund_sp111.yaml.

Build

To build the exporter run:

make build

Only the latest two Go major versions are tested and supported.

Docker

Use Public Image

To start the public available image run:

docker run -it -v "$(pwd)/config.yaml:/config.yaml"  -p 8002:8002 docker.pkg.github.com/hikhvar/mqtt2prometheus/mqtt2prometheus:latest 

Build The Image locally

To build a docker container with the mqtt2prometheus exporter included run:

make container

To run the container with a given config file:

docker run -it -v "$(pwd)/config.yaml:/config.yaml"  -p 9641:9641 mqtt2prometheus:latest 

Configuration

The exporter can be configured via command line and config file.

Commandline

Available command line flags:

Usage of ./mqtt2prometheus.linux_amd64:
  -config string
    	config file (default "config.yaml")
  -listen-address string
    	listen address for HTTP server used to expose metrics (default "0.0.0.0")
  -listen-port string
    	HTTP port used to expose metrics (default "9641")
  -log-format string
    	set the desired log output format. Valid values are 'console' and 'json' (default "console")
  -log-level value
    	sets the default loglevel (default: "info")
  -version
    	show the builds version, date and commit

The logging is implemented via zap. The logs are printed to stderr and valid log levels are those supported by zap.

Config file

The config file can look like this:

# Settings for the MQTT Client. Currently only these three are supported
mqtt:
  # The MQTT broker to connect to
  server: tcp://127.0.0.1:1883
  # The Topic path to subscribe to. Be aware that you have to specify the wildcard. 
  topic_path: v1/devices/me/+
  # Optional: Regular expression to extract the device ID from the topic path. The default regular expression, assumes
  # that the last "element" of the topic_path is the device id.
  # The regular expression must contain a named capture group with the name deviceid
  # For example the expression for tasamota based sensors is "tele/(?P<deviceid>.*)/.*"
  device_id_regex: "(.*/)?(?P<deviceid>.*)"
  # The MQTT QoS level
  qos: 0
cache:
  # Timeout. Each received metric will be presented for this time if no update is send via MQTT
  timeout: 24h
# This is a list of valid metrics. Only metrics listed here will be exported
metrics:
    # The name of the metric in prometheus
  - prom_name: temperature_celsius
    # The name of the metric in a MQTT JSON message. This can be an arbitrary gojsonq path.
    mqtt_name: temperature
    # The prometheus help text for this metric
    help: DHT22 temperature reading
    # The prometheus type for this metric. Valid values are: "gauge" and "counter"
    type: gauge
    # A map of string to string for constant labels. This labels will be attached to every prometheus metric
    const_labels:
      sensor_type: dht22
    # The name of the metric in prometheus
  - prom_name: humidity
    # The name of the metric in a MQTT JSON message
    mqtt_name: humidity
    # The prometheus help text for this metric
    help: DHT22 humidity reading
    # The prometheus type for this metric. Valid values are: "gauge" and "counter"
    type: gauge
    # A map of string to string for constant labels. This labels will be attached to every prometheus metric
    const_labels:
      sensor_type: dht22
    # The name of the metric in prometheus
  - prom_name: heat_index
    # The name of the metric in a MQTT JSON message. Here a nested field.
    mqtt_name: computed.heat_index
    # The prometheus help text for this metric
    help: DHT22 heatIndex calculation
    # The prometheus type for this metric. Valid values are: "gauge" and "counter"
    type: gauge
    # A map of string to string for constant labels. This labels will be attached to every prometheus metric
    const_labels:
      sensor_type: dht22%       

Best Practices

The exporter can only listen to one topic_path per instance. If you have to listen to two different topic_paths it is recommended to run two instances of the mqtt2prometheus exporter. You can run both on the same host or if you run in Kubernetes, even in the same pod.