Error parsing alert "expr" with regular expression in it

Question

I'm trying to define an alert rule with "expr" containing regular-expression

Metric: XYZ-POST-failure-400-1min-rate

- alert: alert_name_here
  expr: __name__=~"(.*)-POST-failure-\d{3}-1min-rate" > 0

Unit testing this using "promtool"

Error
group "group_name", rule 1, "alert_name_here": could not parse expression: parse error at char 10: unexpected character after '=': '~'

Is this even supported by Prometheus alert manager? Can someone guide me on what is the correct way to achieve this?

Thank you

You are missing the brackets `{__name__=~...}` for matching any metric of name matching the regex; this is actually a label matching expression. — Michael Doubez, Oct 28 '19 at 22:46
Thanks for taking time to answer. But including brackets {} will make the YAML invalid — user2922123, Oct 29 '19 at 19:31
Quote the expression to interpret it as a string : `'{__name__=~"..."} > 0'` — Michael Doubez, Oct 29 '19 at 21:20

score 4 · Answer 1 · answered Oct 30 '19 at 22:47

The expression should be a valid PromQL query, you are missing the curly braces to make it a valid vector selector:

{__name__=~"(.*)-POST-failure-\d{3}-1min-rate"} > 0

You can test it in your Prometheus interface.

Regarding the YAML issue of having a leading curly brace, you can use single quotes for which the special character sequences are allowed:

- alert: alert_name_here
  expr: '{__name__=~"(.*)-POST-failure-\d{3}-1min-rate"} > 0'

score 0 · Answer 2 · answered Jan 11 '22 at 12:19

0

I had a very similar error when I twisted the =~ with ~=.

parse error: unexpected character inside braces: '~'

This kind of errors are hard to spot and the error message is not that helpful.

answered Jan 11 '22 at 12:19

konkit

2 Answers2