ListEnabledCheckDefs selected interval_s but never filtered on it, so every
enabled check ran on every 30s pass and the declared per-check intervals were
decorative. Invisible at 17 enabled checks; at ~180 it would have meant ~126
SSH connections every 30s (~363k/day) and `apt update` on every machine every
30 seconds — 14,400 mirror hits a day to answer a question that changes daily.
- check_defs.last_run_at (migration 026) + a due-ness predicate in the query.
A column rather than scheduler memory because this control plane restarts on
every deploy, and an in-memory map would re-fire every check on each restart.
- runCheck stamps last_run_at before processing the result, so a permanently
failing check backs off to its interval instead of re-running every pass.
- updates and backup-freshness drop to daily. Both answer questions whose
answers change about once a day; 60s was just the shared ssh-script default.
- last_run_at is seeded to a random offset within the interval so checks
created by the same seed do not stay in lockstep — otherwise ~165 probes
land in the same instant each minute instead of spread across it.
Deliberately not in the upsert's DO UPDATE: a re-seed must not re-herd them.
Steady state becomes ~180k SSH/day (down from ~363k) and 5 apt runs/day
(down from 14,400), with each 60s check landing at its own point in the minute.
Also renumbers 022→023, 023→024, 024→025: origin/main added its own
022_knowledge_revisions, and prod has already applied version 22. Left
colliding, prod would have skipped the monitoring_spec migration entirely and
then failed the seed on a missing column.
Co-Authored-By: Claude <noreply@anthropic.com>
dtoro
d7b526a112