Docker exporter

Description

A small prometheus exporter used to monitor what cAdvisor does not. It currently supports :

• Docker images :
  • Name
  • Tag
  • Size
  • Number of containers using it
• Docker volumes :
  • Name
  • Mount point
  • Name of docker compose project
  • Number of containers using it
• Docker networks :
  • Name
  • Number of containers using it

Usage

Volumes

The exporter needs access to the docker socket to get the data. You can mount it inside the container :

docker run -v /var/run/docker.sock:/var/run/docker.sock cefadrom/docker-exporter:2

If you want to get the volumes size, you also need to mount the root filesystem inside the container :

docker run -v /var/run/docker.sock:/var/run/docker.sock -v /var/lib/docker/volumes:/var/lib/docker/volumes:ro cefadrom/docker-exporter:2

Note: for security reasons, it is recommended to mount data volumes read-only (using :ro).

Docker compose

The recommended way is to use docker compose. Put the exporter config inside the same docker-compose.yml file as your monitoring stack :

services:
  prometheus:
    image: prom/prometheus:latest
    container_name: prometheus
    volumes:
      - ./prometheus.yml:/etc/prometheus/prometheus.yml
    ports:
      - 9090:9090

  docker-exporter:
    image: cefadrom/docker-exporter:2
    container_name: docker-exporter
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock # To access docker API
      - /var/lib/docker/volumes:/var/lib/docker/volumes:ro # If you want to get volumes size
    ports:
      - 9100:9100

Finally, configure your prometheus.yml file to scrape the exporter. Note that a high scrape interval is recommended as the volume size calculation may be quite resource intensive, and the data does not change that often.

scrape_configs:
  - job_name: 'docker-exporter'
    scrape_interval: 10m
    static_configs:
      - targets: [ 'docker-exporter:9100' ]

Configuration

You can change some of the exporter settings using environment variables:

Environment variable	Default value	Description
CALCULATE_VOLUME_SIZE	TRUE	Enable the volume size calculation using the system command du
REQUEST_TIMEOUT	120s	Time it takes to cancel operations and send the response (valid go duration)

Metrics

Here is a sample of the metrics exposed by the exporter :

# HELP docker_image_size_bytes Size of docker images
# TYPE docker_image_size_bytes gauge
docker_image_size_bytes{id="sha256:efadb309f7ffb875ad073162932b72d0bba5f8da71de54c36055fb843ef31be5",tag="cefadrom/docker-exporter:latest",containers="1"} 217327756
docker_image_size_bytes{id="sha256:3a8d46c63628f568039abf84f17c558cdaf4912d0c54a904e105f93f37f25775",tag="redis:alpine",containers="2"} 37773458

# HELP docker_volume_size_bytes Size of docker volumes
# TYPE docker_volume_size_bytes gauge
docker_volume_size_bytes{name="portainer_portainer_data",mountpoint="/var/lib/docker/volumes/portainer_portainer_data/_data",compose_project="portainer",containers="1"} 573341
docker_volume_size_bytes{name="dockprom_grafana_data",mountpoint="/var/lib/docker/volumes/dockprom_grafana_data/_data",compose_project="dockprom",containers="1"} 1915362
docker_volume_size_bytes{name="dockprom_prometheus_data",mountpoint="/var/lib/docker/volumes/dockprom_prometheus_data/_data",compose_project="dockprom",containers="1"} 1918972991

# HELP docker_network_container_count Number of containers per network
# TYPE docker_network_container_count gauge
docker_network_container_count{id="39b29ca27bc870e8259451db4c13b76ca88a0d211d3fe102eb5689938f094355",name="host",compose_project=""} 0
docker_network_container_count{id="ea78f0a6ef4949b684c155c5b11addb9cd79b7e2c0f7d43791c699373c5ca921",name="proxy",compose_project=""} 3
docker_network_container_count{id="d199cf3d3d45932efc1140e12922b07e8b31ba2715c1f686d44eff19ad7b69c7",name="bridge",compose_project=""} 0
docker_network_container_count{id="e9dcbdd6749b380fcc8789abbe7fe4eeb985110287d6ad4ef71026640688a914",name="none",compose_project=""} 0

# HELP docker_last_scrape_duration_seconds Time it took to scrape docker metrics
# TYPE docker_last_scrape_duration_seconds gauge
docker_last_scrape_duration_seconds 2.755