The Scheduler That Died Standing UpPipeline · medium · ~12 minBetween 00:05 and 00:47 last night, nothing was scheduled. Not failed — *not started*. Forty-two minutes of silence across 1,900 DAGs, discovered at 07:30 when an analyst asked why every morning table was empty.The infuriating part: monitoring shows a green night. The scheduler's health check passed every 30 seconds throughout — the process was up, the port answered, the standby never took over. The scheduler was alive by every probe you had, and dead by the only measure that matters.Leadership wants two things by Friday: an explanation, and a guarantee this class of failure pages within five minutes.Evidence

The silent window

Postmortem fragments

Current monitoring

Checkpoints

The health check passed 84 times during 42 minutes of total scheduling silence. What is the fundamental flaw in the monitoring design?

At ~9,000 evenly-loaded runs/day this would be ~260 missed runs in 42 minutes — but the distribution is midnight-heavy: ~25% of daily runs fire between 00:00 and 01:00. Roughly how many runs were actually delayed in the silent window?

Which monitoring design guarantees this failure class pages within minutes?

Write the Friday plan: the liveness redesign (what the probe must measure), the failover change, and the recovery hazard at 00:47 that your design must also handle (hint: what happened when 41 minutes of runs became eligible at once?).