In this lesson, you will learn how to implement observability layers that track exactly who is accessing your container registry and which specific images are being deployed across your infrastructure.
The Importance of Registry Observability
As we move toward automated deployment patterns and image promotion, the registry becomes the "source of truth" for your artifact supply chain. However, simply storing images isn't enough; you must verify that only authorized CI/CD service accounts are pushing images and only approved production clusters are pulling them. Without auditing, you risk "shadow deployments" where unauthorized entities or compromised runners could pull sensitive images or inject malicious ones.
Implementing Audit Hooks
Most modern container registries (like Harbor, ECR, or Artifactory) provide audit logs that capture metadata for every GET, POST, and DELETE request. To make this actionable, you should stream these logs into a centralized security information and event management (SIEM) system.
For instance, when an image is pulled in a Kubernetes cluster, you can correlate that event with your image provenance data. If you are using admission controllers to enforce image signatures (as discussed in previous lessons), you can cross-reference the cosign verification logs with the registry's access logs.
Consider this audit requirement for a pull event:
{
"timestamp": "2023-10-27T10:00:00Z",
"action": "pull",
"image": "production/app:v1.2.3",
"actor": "k8s-cluster-prod-sa",
"client_ip": "10.0.5.22"
}
Analyzing Usage Trends
Beyond security, auditing helps you optimize costs and storage. By tracking the frequency of image pulls, you can identify "zombie" images that are no longer referenced by any deployment but are still consuming storage quota. If an image has zero pull activity over a 90-day window, your retention policies should trigger an automated cleanup.
To maintain compliance, ensure your audit logs include the User-Agent string, which allows you to distinguish between human developers using docker pull and automated Kubernetes nodes pulling images via containerd or CRI-O.
Key Takeaway: Auditing registry access turns your artifact repository into a transparent, secure ledger, enabling you to detect unauthorized anomalies and optimize lifecycle costs through data-driven usage metrics.