33 lines
1.5 KiB
Markdown
33 lines
1.5 KiB
Markdown
# JT808 Daily Mileage Streaming
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## Scope
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The analytics app can calculate daily mileage from JT808 telemetry only. It consumes `vehicle.event.jt808.v1` and saves the current daily result into the common `vehicle-stat` metric repository.
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## Storage
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Runtime state: none outside `vehicle_stat_metric`. There is no separate JT808 daily-mileage table. 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.
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The JT808 daily-mileage value is calculated from the GPS total mileage reported in location additional information:
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```text
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daily_mileage_km = max_total_mileage_km - min_total_mileage_km
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calculation_method = JT808_TOTAL_MILEAGE_DIFF
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```
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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.
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## Runtime Settings
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Set these in Portainer or Nacos, without committing secrets:
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```text
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KAFKA_TOPIC_JT808_EVENT=vehicle.event.jt808.v1
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VEHICLE_STAT_JT808_MILEAGE_ENABLED=true
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MYSQL_JDBC_URL=<jdbc-url>
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MYSQL_USERNAME=<user>
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MYSQL_PASSWORD=<password>
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```
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Algorithm defaults use the Asia/Shanghai daily boundary. Restart recovery reads the same `daily_mileage_km` metric row.
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