Invalid Prometheus label names prevent all metric export

critical

configurationUpdated Jan 7, 2026(via Exa)

Sources

Metrics | Traefik Hub Documentationdoc.traefik.io

Technologies:

Traefiksubject

PrometheusPrometheus metrics correlate with this issue and help confirm diagnosis

How to detect:

When metrics.prometheus.headerLabels contains invalid Prometheus label names, the entire Prometheus metrics provider fails to serve any Traefik-related metrics. All metric endpoints become non-functional.

Recommended action:

Validate that all label names in metrics.prometheus.headerLabels conform to Prometheus naming rules (alphanumeric and underscores, matching [a-zA-Z_:][a-zA-Z0-9_:]*) before deployment. Review and test headerLabels configuration in non-production environment first.