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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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.
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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 = last_total_mileage_km - first_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 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.
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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, so no separate mileage state store is required.
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