Proposal

Kubernetes SD should be extended so the service, pod, endpoints, and ingress roles can optionally attach extra meta labels based on the namespace and node objects that the targets are discovered in (where appropriate; ingress wouldn't support node meta labels, etc.).

This could be used within Prometheus, but also within Grafana Agent (for traces) and Promtail (for logs) to use this new meta information in similar ways.

Use case. Why is this important?
There are a few use cases for where this would be useful. One such use case has been documented in grafana/agent#980.

Another use case is for filtering targets to scrape to those that exist within specific namespaces. In this scenario, managed namespaces are dynamically created on behalf of users where they have full control over the resources deployed in the environment. The namespace, which users do not have permissions to modify, would have labels or annotations that determine whether scraping is available. This makes checking labels/annotations on the pods inappropriate as users have full control over their contents.