Expose Kubernetes resource namespace metadata in discovery.kubernetes component

[TheoBrigitte]

Request

I would like to be able to use the resource namespace's label in discovery.relabel to filter targets discovered by discovery.kubernetes.

Example:

        discovery.kubernetes "kubernetes_pods" {
          role = "pod"

          attach_metadata {
            namespace = true
          }
        }

        discovery.relabel "kubernetes_pods" {
          targets = discovery.kubernetes.kubernetes_pods.targets

          rule {
            source_labels = ["__meta_kubernetes_namespace_label_foo"]
            regex = "bar"
          }
        }

I expect the above configuration to select all Pods which from every namespace which have the label foo=bar set.

Use case

I am aware of the loki.source.podlogs component which would allow to select pods using a namespace label selector, but I would like to avoid the overhead of tailing logs via the Kubernetes API server, this is because I operate a large solution with multiple cluster running over 3000 pods.

[mattdurham]

This would require something similar to #1541 to alloy merging metadata labels to file based discovery.

[TheoBrigitte]

Well AFAIU this would not solve my case. join would allow to enrich targets with additional labels, but yet there would be no way to pass the resulting receiver capsule to loki.source.file as it only accepts targets as arguments.