47 lines
1.6 KiB
Markdown
47 lines
1.6 KiB
Markdown
# JT808 Kafka Streaming Mileage Plan
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## Current Goal
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Consume JT808 Kafka location events and write the derived daily mileage into the common vehicle-stat metric repository.
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## Current Design
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- Source topic: `vehicle.event.jt808.v1`
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- Runtime app: `vehicle-analytics-app`
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- Runtime state: none outside `vehicle_stat_metric`
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- Metric output: `VehicleStatRepository.recordDailyMileageSample(...)`
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- Production metric storage: JDBC/MySQL `vehicle_stat_metric`
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- Date boundary: `Asia/Shanghai`
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- Calculation method: `JT808_TOTAL_MILEAGE_DIFF`
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JT808 daily mileage is calculated only from the GPS total mileage reported by JT808 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 first valid local-day sample writes `daily_mileage_km=0.0`. Later samples update the same metric row with:
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```text
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metric_value = latest_total_mileage_km - first_total_mileage_km
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metric_key = daily_mileage_km
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```
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The first and latest GPS total mileage values stay on that same metric row as calculation source columns so restarts recover from MySQL without Redis or another state table.
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## Runtime Properties
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```text
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KAFKA_TOPIC_JT808_EVENT=vehicle.event.jt808.v1
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VEHICLE_STAT_ENABLED=true
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VEHICLE_STAT_JT808_MILEAGE_ENABLED=true
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VEHICLE_STAT_REPOSITORY_TYPE=jdbc
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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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## Notes
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Do not create or write a protocol-specific JT808 daily-mileage table. Do not add distance accumulation, integral calculation, Redis state, or memory state back into this path unless the mileage definition changes again.
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