These actions simlify metrics filtering. For example,
- action: keep_metrics
regex: 'foo|bar|baz'
would leave only metrics with `foo`, `bar` and `baz` names, while the rest of metrics will be deleted.
The commit also makes possible to split long regexps into multiple lines. For example, the following config is equivalent to the config above:
- action: keep_metrics
regex:
- foo
- bar
- baz
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.
