Prometheus 2: Invalid characters in recording rule names are silently allowed (and break things)

[EdSchouten]

#So here I am, migrating a recording rule from Prometheus 1 to an instance running 2.0.0-rc0:

banana{color="yellow"} = strawberry{flavor="sweet"}

Prometheus 2 uses YAML. Let's try this?

- record: banana{color="yellow"}
  expr: strawberry{flavor="sweet"}

Interesting: Prometheus starts properly and the rule gets displayed on the rules page. Yet, I can't seem to get any results when using simple queries like banana. Well, as it turns out, the recording rule above introduces an actual metric with name banana{color="yellow"}; not banana. You end up with metrics along this shape: banana{color="yellow"}{flavor="sweet"}. The only way you can access them is if you use queries like {__name__=~"banana.*"}.

Reading some more documentation, it looks like I need to do this instead:

- record: banana
  expr: strawberry{flavor="sweet"}
  labels:
    color: yellow

Question: would it make sense to add some kind of safety belt to the recording rules parser to reject names that don't match [a-zA-Z_:][a-zA-Z0-9_:]*?

[lock]

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