Possibly redundant loki label drop of structured metadata values

[marshallford]

Hello 👋🏼 ,

I often look over the helm templates and examples provided by this project when developing/troubleshooting Alloy configs. In any case, while working on adding structured metadata to Loki logs I noticed labels used for structured metadata values were missing from the log entries (without the use of a stage.label_drop block). This initially confused me because I recalled that this chart specifically dropped all labels passed to this block afterwards -- presumably to avoid data duplication.

Long story short, it seems as though the stage.structured_metadata block in the loki.process component removes/converts labels when setting structured metadata values. I opened a docs PR with more info here: grafana/alloy#1810. I suspect that the helm template snippet which drops labels used for structured metadata values can be safely removed.

The aforementioned helm template:

k8s-monitoring-helm/charts/k8s-monitoring-v1/templates/alloy_config/_pod_logs_processor.alloy.txt

Lines 39 to 52 in 4c6ee1a

	// Drop the filename label, since it's not really useful in the context of Kubernetes, where we already have cluster,
	// namespace, pod, and container labels. Drop any structured metadata. Also drop the temporary
	// container runtime label as it is no longer needed.
	stage.label_drop {
	values = [
	"filename",
	"tmp_container_runtime",
	{{- if .Values.logs.pod_logs.structuredMetadata }}
	{{- range $label, $lokiLabel := .Values.logs.pod_logs.structuredMetadata }}
	{{ $lokiLabel | default $label | quote }},
	{{- end }}
	{{- end }}
	]
	}

Thank you!