Symptom

Up to Promregator version 0.5.0 (excluding), a rewriting rule is necessary for running Promregator in Single Target Scraping mode. The Prometheus' configuration may contain the following block

relabel_configs:
- source_labels: [__meta_promregator_target_path]
  action: replace
  target_label: __metrics_path__
  regex: (.+)

Background / Root Cause

The relabeling configuration in the configuration file of Prometheus is required, as Promregator only exposed the metadata label __meta_promregator_target_path for specifying the path where Single Target Scraping shall take place.

Starting with 0.5.0, Promregator also sets the metadata label __metrics_path__ for inbound requests of the endpoint at /discovery. This makes the relabeling configuration superfluous.

Solution

When upgrading or starting to use Promregator version 0.5.0 or later, it is recommended to remove the relabel configuration from the Prometheus' configuration file to prevent collisions.

References

• This approach has also been initiated by https://github.com/prometheus/docs/pull/1190.