Non-greedy regex in relabel_configs fails

[pete0emerson]

Suppose __meta_consul_tags value is ,environment:stage,application:webapp,.

With a config of:

    - source_labels: ['__meta_consul_tags']
      regex:         ',environment:(.*),'
      target_label:  'environment'
      replacement:   '$1'

I get: environment="stage,application:webapp".

That makes sense, because my regular expression is greedy and blowing past the first comma.

If I change it to be non-greedy:

    - source_labels: ['__meta_consul_tags']
      regex:         ',environment:(.*?),'
      target_label:  'environment'
      replacement:   '$1'

The results are unchanged: environment="stage,application:webapp".

Interestingly enough, if I change my regex to:

    - source_labels: ['__meta_consul_tags']
      regex:         ',environment:([a-z]*),'
      target_label:  'environment'
      replacement:   '$1'

The results come back empty, i.e. no new labels are created.

[brian-brazil]

This is a consequence of the regex being anchored and you not having (.*) on either end.

[pete0emerson]

Ah, anchoring on both ends, yes, got it. (ref #1519 #1518)

Worth better documentation.

[grobie]

prometheus/docs#370

[lock]

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