dockerhub_ratelimit_exporter

A Prometheus-format exporter to report on DockerHub per-image rate limits.

Recently, DockerHub has introduced rate limiting for anonymous and free-tier users. This exporter can help Prometheus users track the remaining pulls for certain images.

Status/Roadmap

This is brand-new, hacked-together over the course of a couple hours. It works, but I'm certain there are bugs.

This is currently very thin on features. Some things that are missing:

• support for authenticating to DockerHub
• support for caching auth tokens on a per-repo basis
• exposing a few more general-purpose metrics

Usage

The image name is provided as a query parameter when querying the exporter, and Prometheus-format metrics are returned, like this:

$ curl http://localhost:9766/limits?image=hairyhenderson/gomplate:v3.8.0
# HELP dockerhub_ratelimits_limit total number of pulls that can be performed during the window
# TYPE dockerhub_ratelimits_limit gauge
dockerhub_ratelimits_limit{image="hairyhenderson/gomplate:v3.8.0"} 100
# HELP dockerhub_ratelimits_remaining number of pulls remaining for the window
# TYPE dockerhub_ratelimits_remaining gauge
dockerhub_ratelimits_remaining{image="hairyhenderson/gomplate:v3.8.0"} 100
# HELP dockerhub_ratelimits_window_seconds the length of the time window
# TYPE dockerhub_ratelimits_window_seconds gauge
dockerhub_ratelimits_window_seconds{image="hairyhenderson/gomplate:v3.8.0"} 21600

Prometheus Configuration

When using Prometheus to scrape the exporter, the image parameter can be provided like this:

scrape_configs:
  - job_name: hub-limits
    scrape_interval: 15s
    metrics_path: /limits
    params:
      image:
        - busybox
        - hairyhenderson/gomplate:v3.8.0
        - prom/prometheus:v2.22.1
    static_configs:
      - targets:
        - localhost:9766

License

The MIT License

Copyright (c) 2020 Dave Henderson