Discover docker containers to scrape based on labels

This tool aims at discovering containers running with prometheus.io/scrape=true annotations from a given docker engine, and auto-configure prometheus for scraping.

This tool is standalone and write the discovered containers (services) in a file, which is in turn passed to Prometheus file service discovery to start the scraping jobs.

Example via a docker-compose

The following part is giving a complete example of configuring the docker-labels discovery mechanism. It is based in three parts, namely:

• Configure prometheus-docker-labels-discovery
• Configure Prometheus file_sd_configs
• Configure your services

Configure prometheus-docker-labels-discovery

  prometheus-docker-labels-discovery:
    image: sqooba/prometheus-docker-labels-discovery:v1
    restart: unless-stopped
    networks:
      - monitoring_default # make sure this network exists and is connected to prometheus
#    ports:
#      - "8080"
    security_opt:
      - no-new-privileges:true
    volumes: # Mount the JSON file that will be exchanged with prometheus
      - ./from-docker-labels.json:/tmp/from-docker-labels.json
    environment:
      - PROMETHEUS_CONFIG_FILE_PATH=/tmp/from-docker-labels.json
      - DOCKER_NETWORK_NAME=bridge
      - PROMETHEUS_COMMON_LABELS=commonlabel1=commonvalue1

Configure Prometheus

Prometheus needs to be configured using file_sd_configs scrape config.

scrape_configs:
- job_name: 'docker-labels-sd'
  file_sd_configs:
  - files:
    - 'from_docker_labels.json'

Configure your services

Any service can now be configured using docker labels. The following example shows in docker-compose style how this looks like:

services:
  test-metrics:
    image: dummy-metrics:v1
    labels:
      - "prometheus.io/scrape=true"
      - "prometheus.io/path=/metrics"
      - "prometheus.io/extra-labels=k1:v1,k2:v2"

The exhaustive list of labels to configure properly your service is provided below:

Annotation	Definition	Example
prometheus.io/scrape	Main label to ensure this container will be scraped by Prometheus. Required value is true. Any other value will not be considered.	prometheus.io/scrape=true
prometheus.io/port	Specify which port to use for the scraping. In case of a single port exposed, this configuration can be omitted.	prometheus.io/port=8080
prometheus.io/path	Alternative path for scraping the metrics. Default from Prometheus is /.	prometheus.io/path=/metrics
prometheus.io/scheme	Alternative scheme for scraping thee metrics. Default from Prometheus is http.	prometheus.io/scheme=https
prometheus.io/extra-labels	Any extra labels to add to the metrics scraped for this container. Comma separated key:value pairs.	prometheus.io/extra-labels=label1:value1,label2:value2,...