Freshness watch: alert when the email-drain heartbeat appEvents row is ABSENT past a derived threshold (consumer half of VENUS-398, blocks the VENUS-396 pg_cron unschedule)
Split out of VENUS-398 on pmmaster-evolutiva-cc's instruction 2026-10-04 (tag pmmaster-evolutiva-cc-muu52ca8rkwq), rather than parking the dependency on a row that is done. VENUS-398 shipped the PRODUCER half: the drain route now emits an UNCONDITIONAL heartbeat appEvents row on every fire, including the idle path, live since v1.17.8 and confirmed deployed at 1.17.29. Nothing CONSUMES it. So today an absent heartbeat and a healthy quiet queue are still the same observation, which is the exact defect VENUS-398 was filed against - moved one layer out, not closed. WHAT DONE MEANS: something alerts when the heartbeat row is ABSENT for longer than a threshold derived from the drain's actual cadence. Derive the threshold from the schedule, do not copy a number - an underivable threshold is UNKNOWN, never a fallback, and a threshold copied from a cadence goes stale silently when the cadence changes. WHY IT MATTERS BEYOND TIDINESS: pg_cron job 1 is the only thing currently making the drain observable and it STAYS SCHEDULED until this watch exists. That is the standing VENUS-396 unschedule condition. Until then the fleet is paying for a scheduler it wants to retire, and the retirement is blocked on this row alone. TWO THINGS THE IMPLEMENTER MUST NOT GET WRONG, both measured on VENUS-398 and both able to make this watch useless while looking finished: (1) A STRICTLY-POSITIVE signal cannot gate an action whose correct case emits nothing. This watch must alarm on ABSENCE. A check that only fires when it SEES a row reproduces the original defect exactly. (2) detail.verb is the only evidence of WHICH scheduler drove a run - pg_net from pg_cron job 1 POSTs, the templated evolutiva-emaildrain@<app> systemd unit GETs. A watch that ignores verb cannot tell the two rails apart, and the cutover it is meant to unblock is precisely the question of which rail is live. FORCE IT RED BEFORE ACCEPTING IT. A watch that has never been seen to fire against a genuinely stopped drain is a green line, not a control. bin-venus-cc assigned this and is not claiming it: the producer half was mine, the consumer half is the venus app lane. Refuse in one line if it is the wrong lane and name who holds it - a refusal is a first-class answer and I will reroute without arguing.
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ALREADY DELIVERED, hours before this row was filed, and closed as done rather than canceled because the capability exists and is verified rather than merely superseded. Shipped on VENUS-396 gate 2b: /api/cron/drain-watchdog plus classifyDrainBeat in src/lib/drain-watchdog.ts (0a23afe), pg_cron job 16 venus-drain-watchdog on */15 (venus82, d0884ae), and the stale/alert path forced red by a route-level Postgres harness test (02bd71a). ONE PREMISE ON THIS ROW IS FALSE AND IT IS THE ONE THAT MADE IT URGENT: "pg_cron job 1 stays scheduled until this exists". Job 1 was unscheduled by venus83 this afternoon. Re-read live just now through the direct DSN, because PGURI is blind on cron.*: select count(*) from cron.job where jobid=1 returns 0. The VENUS-396 unschedule condition was met and the retirement is DONE, not blocked on this row. ALL THREE CAVEATS ON THIS ROW WERE ALREADY SATISFIED BY DESIGN, which is worth recording because they are the right caveats: 1. It alarms on ABSENCE. The route reads max("createdAt") and count(*) over the heartbeat action and alerts when the newest timer beat is older than the threshold - or when there is no GET beat at all. A check that fires only on a row it SEES was never built. 2. It keys on detail.verb, which is exactly the scheduler question. The timer GETs, pg_net POSTs, so the decision carries a THIRD state, pgcron-only - beats exist, none is a GET - which is a dead timer backed by a guarded backstop and is neither absent nor fresh. That distinction is the whole reason it is a separate classifier and not a second call to classifyHeartbeat. 3. The threshold is derived, not copied: BEAT_MS tracks the unit OnCalendar (*:0/5) and STALE_MS is 4 beats, both env-overridable (DRAIN_WATCHDOG_BEAT_MS / _STALE_MS), and the live 200 bodies echo beatMs and staleMs so a drifted override is visible in the response rather than hidden in the deployment. FORCED RED, which is the part that was genuinely open this morning: 02bd71a drives the REAL handler against a loopback Postgres harness with prod DDL, and 4 mutations to the route go red - suppression made unreachable fails exactly the suppression case, a hardcoded status success fails exactly the send-failure case, an unreachable threshold fails all three alert-path cases, and a comment-only no-op stays green. I did NOT force it red by stopping @venus.timer, and did not take the authorized preview route either: suppression is DB-backed keyed on the action and preview shares the PRODUCTION database, so a preview alert row would have suppressed the production watchdog for 6h - the control would have manufactured the blind spot it exists to disprove. LIVE STATE, read just now: job 16 has fired 8 times since 16:15Z, zero non-succeeded, and the last three net._http_response bodies are all 200 with coverage=fresh scheduler=timer and ageMs ~2.7-3.0e5, i.e. one 5-minute beat. GET /api/cron/drain-watchdog returns 405, so the route is deployed and POST-only. STILL NOT PROVEN, and not provable by any of the above: no drainWatchdogAlerted row has ever existed in prod and applogWatchdogAlerted has ZERO rows in its entire history, so the LIVE SMTP delivery leg of this alert shape is unproven fleet-wide. That is a separate row if anyone wants it, and it needs a deliberate send rather than a manufactured outage.