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freshness_timestamp_metric: age via time() - max() (6-significant-digit scalar rounded the timestamp by 50 min) #2530

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Merged
Flotapponnier merged 1 commit into from
Sep 19, 2026
Merged

freshness_timestamp_metric: age via time() - max() (6-significant-digit scalar rounded the timestamp by 50 min) #2530

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9 changes: 6 additions & 3 deletions src/lib/materialize/load.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1223,9 +1223,12 @@ async function tryLoadLive(
// executions are pulses, an instant query on them is empty between
// runs and used to fall back to "now", so a dead harness read as
// "updated 4 min ago" forever).
const lastTs = await prom.scalar(`max(${freshnessTsMetric})`);
if (lastTs != null && Number.isFinite(lastTs) && lastTs > 1_600_000_000) {
lastRunAt = new Date(lastTs * 1000).toISOString();
// Ask Prometheus for the AGE, not the timestamp: prom.scalar keeps
// 6 significant digits, which rounds a unix time to the nearest
// ~1000 s (18:36:50 came back as 17:46:40 on 2026-09-19).
const ageSec = await prom.scalar(`time() - max(${freshnessTsMetric})`);
if (ageSec != null && Number.isFinite(ageSec) && ageSec >= 0 && ageSec < 10 * 365 * 86_400) {
lastRunAt = new Date(Date.now() - Math.floor(ageSec * 1000)).toISOString();
} else {
// No run recorded at all: say so rather than pretending.
lastRunAt = new Date(0).toISOString();
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