These actions may be useful for filtering out unneeded targets and/or metrics if they contain equal label values.
For example, the following rule would leave the target only if __meta_kubernetes_annotation_prometheus_io_port
equals __meta_kubernetes_pod_container_port_number:
- action: keep_if_equal
source_labels: [__meta_kubernetes_annotation_prometheus_io_port, __meta_kubernetes_pod_container_port_number]
This should reduce CPU load during scraping when target discovery generates
big number of `__meta_*` labels (for instance, k8s discovery).
See https://www.robustperception.io/life-of-a-label for details.
