The alert manager kept its cooldowns and its ceiling per hour in memory, so a
node that stayed down was announced again by every restart. Each delivered
alert is now a row in the new alert_sent table (additive migration), loaded
for the last seven days when the manager starts and pruned as new ones come
in. A ledger that fails never stops an alert. The manager's clock is wall
time for the same reason.
A node_health "down" alert also waits 60 s (HEALTH_GRACE_S) in a pending task
per node; a later event that is not "down" cancels it, as does stopping the
manager, so a broker restarting with the stack alerts nobody.
The cooldown used to be stamped before the ceiling per hour was checked, so
an alert the ceiling held back still spent its cooldown. It is stamped only
once the alert is sent now.
Claude-Session: https://claude.ai/code/session_01SSi5AvZ7pFmySK8zy3NPMh
stroblme
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