Signal Forge ADR-009: K8s attribute enrichment at collector (not in SDK)

Signal Forge ADR-009: K8s attribute enrichment at collector (not in SDK)

Status: Accepted

Decision: K8s pod/namespace/deployment attributes are added by otelcol.processor.k8sattributes in the Helm-managed Alloy stack, not by the application SDK.

Rationale:

• Application code should not know about Kubernetes. K8s attributes are infrastructure metadata.
• Centralised enrichment means adding a new service to the cluster gets K8s attributes automatically — no SDK change required.
• The k8sattributes processor uses the OTLP connection source IP to look up the pod in the Kubernetes API, which is accurate and requires no application-side configuration.
• The processor requires a ClusterRole with get/list/watch on pods and nodes. This is one configuration point for the entire cluster, not per-service.

Alternative considered: OTEL_RESOURCE_ATTRIBUTES env var per Deployment — rejected because it requires manual maintenance and is inaccurate (pod name changes on each restart; it would always show the previous name unless the env var uses the Downward API).