HomeCentr - dockerd-exporter

This image is based on the original [dockerd-exporter] by Stefan Prodan. Docker daemon exposes natively metrics in Prometheus compatible format. In Swarm environment, Prometheus would be only able to reach the metrics of the node it is running on. This container allows exposing these metrics into an overlay network. This way Prometheus can just scrape the containers.

Usage

version: "3.7"
services:
  dockerd-exporter:
    build: .
    image: homecentr/dockerd-exporter

Exposing metrics on Docker daemon

Please note that the metrics are currently not exposed by default. It requires enabling experimental features as described in the Docker docs.

Environment variables

Name	Default value	Description
PUID	7077	UID of the user dockerd-exporter should be running as. The user does NOT require access to Docker socket.
PGID	7077	GID of the user dockerd-exporter should be running as. The group does NOT require access to Docker socket.
DOCKERD_HOST	172.17.0.1	IP address or hostname of the daemon exposing the metrics. Please see the notes below.
DOCKERD_PORT	9323	Port on which the metrics are exposed. 9323 is the value used by Docker docs so the image uses it as default.

Docker daemon IP address/hostname

There is really no universal value which would work everywhere. Known options:

• For Docker on Linux, you can use 172.17.0.1 (the default value). This IP is not really documented so it is not guaranteed to work on every installation.
• For Docker Desktop for Mac and Windows, you can use the host.docker.internal alias. Please note that this alias only works if the container is explicitly connected to a network.
• If you connect the container to the host network, you can use localhost irrespective of the platform.

Exposed ports

Port	Protocol	Description
9323	TCP	HTTP endpoint with the metrics in Prometheus compatible format.

Volumes

This container does not expose any volumes.

Security

The container is regularly scanned for vulnerabilities and updated. Further info can be found in the Security tab.

Container user

The container supports privilege drop. Even though the container starts as root, it will use the permissions only to perform the initial set up. The dockerd-exporter process runs as UID/GID provided in the PUID and PGID environment variables.

⚠️ Do not change the container user directly using the user Docker compose property or using the --user argument. This would break the privilege drop logic.