KEP-6053: Kubelet Image Garbage Collection Observability

[mattsu2020]

What changed

Adds a new SIG Node KEP for improving kubelet Image Garbage Collection observability.

The KEP proposes low-cardinality kubelet metrics for Image GC attempts, duration, reclaim targets, estimated reclaimed bytes, image deletion outcomes, skipped images, image filesystem usage, and failure/no-op outcomes.

Why this is needed

Kubelet currently exposes kubelet_image_garbage_collected_total{reason}, which only counts successfully removed images. Operators cannot reliably tell whether Image GC is running, failing, doing no work, running slowly, or reclaiming less space than requested without inspecting kubelet logs node by node.

Notes

This proposal is passive observability only. It does not change Image GC policy, kubelet configuration, Kubernetes APIs, CRI APIs, pod behavior, or eviction behavior.

Validation

• make update-toc
• make verify-toc
• make verify-metadata

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: mattsu2020
Once this PR has been reviewed and has the lgtm label, please assign mrunalp for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• keps/sig-node/OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Hi @mattsu2020. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.