Traffic absent alerts causing pager noise
## Summary We're getting a lot of pages for sparse metrics (metrics that are intermittently reported). When they go missing, we get alerted because traffic seems to be "absent" - but there was never any traffic in the first place. I suspect it has something to do with how we're using `offset 1h` or `unless` on our alerting rules. ## Related Incident(s) * https://gitlab.com/gitlab-com/gl-infra/production/-/issues/8520 * https://gitlab.com/gitlab-com/gl-infra/production/-/issues/8507 ## Desired Outcome/Acceptance Criteria We are no longer getting `*TrafficAbsent` alerts for things that had no traffic to begin with. ## Associated Services <!-- Apply the appropriate services associated with this corrective action if applicable. --> ## Corrective Action Issue Checklist * [x] Link the incident(s) this corrective action arose out of * [x] Give context for what problem this corrective action is trying to prevent from re-occurring * [x] Assign a severity label (this is the highest sev of related incidents, defaults to 'severity::4') * [x] Assign a priority (this will default to 'Reliability::P4')
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