38 lines
1.7 KiB
Markdown
38 lines
1.7 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`, keeps the rolling per-vehicle daily state in Redis or memory, 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. Runtime state is stored under the configured JT808 state store so the stream can continue after restart. The derived metric is written through `VehicleStatRepository.saveDailyStat(...)`; production uses the common JDBC/MySQL metric table `vehicle_stat_metric`. Local development can force the file fallback with `VEHICLE_STAT_REPOSITORY_TYPE=file`, which writes `daily-stats.tsv` under `VEHICLE_STAT_FILE_PATH`.
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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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```
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The metric is saved only after at least two ordered JT808 location points with valid `total_mileage_km` have been received for the same vehicle and local day. If the difference is negative, no metric row is saved for that state update.
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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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VEHICLE_STAT_REPOSITORY_TYPE=jdbc
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VEHICLE_STAT_JT808_STATE_STORE=redis
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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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REDIS_HOST=<host>
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REDIS_PORT=6379
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REDIS_DATABASE=50
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REDIS_PASSWORD=<password>
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```
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Algorithm defaults use the Asia/Shanghai daily boundary. The rolling state stores only the fields needed by the GPS total-mileage difference calculation.
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