CRONOS Audit Trail
Trace
Objective
Diagnose PROBLEM ENG-DIAG-001 — 'The nightly export went silent' — to identify root cause of 0-row CSV exports, explain why failure stayed silent (exit 0, 'export complete'), and prescribe fix + preventive measure.
Step-by-step trace
Diagnose PROBLEM ENG-DIAG-001 — 'The nightly export went silent' — to identify root cause of 0-row CSV exports, explain why failure stayed silent (exit 0, 'export complete'), and prescribe fix + preventive measure.
time_zone_mismatch2026-07-19T01:14:21.080404+00:00The deploy changed :since/:until to UTC, but the server's clock is UTC-3, causing the query to select a time window that falls entirely in the future relative to actual order timestamps.
empty_orders_table2026-07-19T01:14:21.885334+00:00The orders table is actually empty for the last 3 days, despite being confirmed non-empty — perhaps the confirmation was wrong or outdated.
broken_query_logic2026-07-19T01:14:22.742137+00:00The SQL query itself is malformed or contains a logic error (e.g., incorrect column name, broken WHERE clause) that causes it to return no rows.
3 nights ago, a deploy changed how :since and :until are computed: from naive server-local time to UTC, using the server's clock which is set to UTC-3.
The orders table is confirmed non-empty: ~40,000 rows are inserted every day, including during the last 3 days.
Database permissions are unchanged. The S3 upload succeeds (it uploads the header-only CSV).
empty_orders_table2026-07-19T01:14:30.944629+00:00Directly refuted by confirmed presence of ~40,000 daily orders.
broken_query_logic2026-07-19T01:14:31.740482+00:00Refuted by unchanged permissions and successful S3 upload — query executed and returned zero rows, not an error or permission failure.
The export code wraps the whole run in a broad `try/except Exception` that logs 'export complete' and returns, regardless of what happened inside.
ROOT CAUSE: time_zone_mismatch — UTC-based :since/:until computed on a UTC-3 server causes the query to target a future time window, returning zero rows. SILENCE: caused by broad `try/except Exception` swallowing all errors and logging 'export complete' unconditionally. FIX: compute :since/:until in the server's local timezone (UTC-3) or correct the server clock to UTC. PREVENTION: replace broad exception handler with specific error handling and non-zero exit on failure; add a row-count assertion before upload.
Hypotheses
| Label | Status | Outcome |
|---|---|---|
| time_zone_mismatch | Active | The deploy changed :since/:until to UTC, but the server's clock is UTC-3, causing the query to select a time window that falls entirely in the future relative to actual order timestamps. |
| empty_orders_table | Discarded | Directly refuted by confirmed presence of ~40,000 daily orders. |
| broken_query_logic | Discarded | Refuted by unchanged permissions and successful S3 upload — query executed and returned zero rows, not an error or permission failure. |
Decision
- Confidence 19/20 capped at 3/5 (diversity ceiling: 1/3 observation groups)
chain_ok : true