1.6 KiB
JT808 Daily Mileage Streaming
Scope
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.
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 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:
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 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
Set these in Portainer or Nacos, without committing secrets:
KAFKA_TOPIC_JT808_EVENT=vehicle.event.jt808.v1
VEHICLE_STAT_JT808_MILEAGE_ENABLED=true
MYSQL_JDBC_URL=<jdbc-url>
MYSQL_USERNAME=<user>
MYSQL_PASSWORD=<password>
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.