label with regex- Prometheus

Question

I'm trying to add a new label with regex. the name instance is pr-na01-na02-A I'm trying to get only the pr-na01, so I did this:

  - source_labels: ['__meta_ec2_tag_Name']
    regex: '^[^-]*-[^-]*'
    target_label: 'test'
    replacement: '$1'

and still don't see a new label (test) under Prometheus metrics.

Answer 1

The issue is that you have no capture groups, so $1 is empty. Also you're not matching the full string.

Try (^[^-]*-[^-]*).* as the regex.