Prometheus-to-MQTT

Scraping metrics from Prometheus and sending them to MQTT broker.

Why?

I was trying to build small dashboard on my phone, which would pull the metrics from MQTT broker. I've noticed that I already have a lot of metrics stored in prometheus, so I wanted to re-use them.

How?

Edit config.yaml file, build the program and run it:

CGO_ENABLED=0 go build -o prometheus2mqtt . && ./prometheus2mqtt 

Docker

...or use this docker image: https://hub.docker.com/r/krzysztofgzocha/prometheus2mqtt Currently just a few OS/arch are ready and the build is not yet automated.

Config options

prometheus_url: http://prometheus:9090
interval: 15s
scrape_timeout: 3s
mqtt:
  user: admin
# user_file: /var/secret/user # Useful when using docker secrets 
  password: admin
# password_file: /var/secret/user # Useful when using docker secrets
  servers:
    - mqtt://mosquitto:1883
  insecure_skip_verify: true
  publish_topic_prefix: p2m
  client_id: Prometheus2MQTT
  retain_messages: true
  publish_timeout: 5s
  qos: 1
  ha_publisher: true # Should it be compatible with HomeAssistant MQTT discovery?
  discovery_prefix: homeassistant
metrics:
  - name: "Health: Prometheus"
    query: up{job='prometheus'}

Metrics format

In order to configure metrics we have to specify 2 value for each of them:

• name: easy to read name, which will be sent to MQTT broker and could be picked up in the topic p2m/<name>. All non-alfanumeric characters will be replaced with _ when constructing MQTT topic.
• query: used to query Prometheus