Ruler: rule group limit enforcement has off-by-one error

[mattmendick]

Describe the bug
The ruler seems to have an issue where the rules per group limit is forcing one fewer than the limit, yielding an error message like this:

per-user rules per rule group limit (limit: 15 actual: 15)

To Reproduce
Submit a rule group with the same number of rules as the limit, ie: 15 rules in a group with the limit set to 15.

Expected behavior
The submitted rule group should be allowed to contain up to and containing the limit specified. The limit set to 15 should allow a group with 15 rules to be accepted.

[stale]

This issue has been automatically marked as stale because it has not had any activity in the past 60 days. It will be closed in 15 days if no further activity occurs. Thank you for your contributions.

[pracucci]

Still valid

[mtanda]

@pracucci
We hit this issue in Grafana Cloud. Do you have plan to fix this?

[pracucci]

Do you have plan to fix this?

There's an open PR #3616 which got stuck. I talked to Matt -- the PR author -- and they're fine if anyone takes it over.

[pracucci]

Fixed in #3616.

[mtanda]

Thanks for quick fix!