garbage

Google Artifact Registry Brutally Automatic Garbage Eradicator (Garbage) deletes unused images from Google Artifact Registry (GAR).

Garbage periodically cross-references images in GAR with resources in Kubernetes and notes which images are in use. After a certain grace period, images no longer in use are deleted.

Detailed algorithm

• Query the Google Artifact Registry (GAR) API to fetch all image metadata in a given project
• Store the image metadata (id, name, tag, shasum) in a database
• Query all Kubernetes clusters through nais/api to fetch all image references
  • From ReplicaSet, Job, CronJob, StatefulSet, DaemonSet.
• Generate deletion candidates using the garbage collection approach (collect and sweep):
  • Initialize empty hashmap with all images from GAR. Set refcount to 0.
  • Cross-reference images from Kubernetes with GAR images. Increment refcount by 1 for each match.
  • For each image with refcount>0, recursively find parent references and increment refcount by 1 for each match.
  • All images with refcount>0 are marked as seen in the database with a timestamp.
• Delete images that haven't been seen recently (within a given threshold, e.g. 30 days)