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fix: calculate jt808 daily mileage from metric endpoints

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lingniu
2026-07-01 09:52:24 +08:00
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docs/operations/jt808-daily-mileage-runbook.md
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@@ -6,16 +6,16 @@ The analytics app can calculate daily mileage from JT808 telemetry only. It cons
## Storage
There is no separate JT808 daily-mileage table and no Redis mileage state. The derived value is stored as one `daily_mileage_km` metric row in the common JDBC/MySQL table `vehicle_stat_metric`; the first and latest GPS total mileage values are kept on that same row as calculation source columns.
There is no separate JT808 daily-mileage table and no Redis mileage state. The derived value is stored as one `daily_mileage_km` metric row in the common JDBC/MySQL table `vehicle_stat_metric`; the local-day minimum and maximum GPS total mileage values are kept on that same row as calculation source columns.
The JT808 daily-mileage value is calculated from the GPS total mileage reported in location additional information:
```text
daily_mileage_km = last_total_mileage_km - first_total_mileage_km
daily_mileage_km = max_total_mileage_km - min_total_mileage_km
calculation_method = JT808_TOTAL_MILEAGE_DIFF
```
The first valid JT808 location point for a vehicle and local day stores the day start total on the metric row and writes `daily_mileage_km=0.0`. Later ordered points update the latest total on the same row and rewrite the derived `daily_mileage_km`. If a later total mileage is lower than the stored latest total, the previous latest total remains.
The first valid JT808 location point for a vehicle and local day stores both calculation endpoints on the metric row and writes `daily_mileage_km=0.0`. Later ordered or replayed points update the lower endpoint when the reported GPS total mileage is smaller, update the upper endpoint when it is larger, and rewrite the derived `daily_mileage_km` on the same row.
## Runtime Settings