Add Dangerbot rule to suggest adding specs for Redis/HLL metrics migration
Problem
Currently when we migrate Redis/HLL we need to add the old->new keys pair to override.yml
files in order to count pre-migration values in the counters.
The process is error prone since a typo in the new key name or error in applied label would lead to incorrect values (metric fails to merge old and new values)
Desired Outcome
A first iteration could be to add a Dangerbor rule to suggest adding spec for the migrated keys.
Potential Solution
How to verify
Further actions needed
Further work to add a reusable solution is planned in another issue.