trip-updogger

Tiny async Python service that bridges OwnTracks location events via MQTT to GTFS-RT Trip Updates in Redis.

Part of a larger stack; see deploy-gtfs-rt for the full deployment.

How it fits together

OwnTracks app (phone)
    └─> MQTT broker
            └─> trip-updogger
                    └─> Redis (trip_update:{trip_id} keys)
                            └─> cafe-car (serves GTFS-RT feeds)

On each location event, the service queries PostgreSQL for the vehicle's stop times (resolving the MQTT device name through a tripalias table), computes the current delay against the schedule, and writes a Trip Update to Redis. If the MQTT connection drops, it reconnects with exponential backoff (1s → 60s max).

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Payload transformation

Each OwnTracks location event is decoded as follows:

OwnTracks field	Meaning	Notes
topic owntracks/{user}/{device}	driver, trip_id	user maps to a driver row (for feed lookup); device is used as the alias to resolve to a real trip_id
lat, lon	vehicle position	used to compute delay against scheduled stop times
tst	timestamp	seconds since epoch; used to determine time-of-day for schedule lookup
cog	bearing	degrees; not written to Redis
vel	speed	km/h; not written to Redis

Redis key: trip_update:{device} — written on each location update (key uses the alias/device name).

Redis value:

{"trip_id": "...", "vehicle_id": "...", "timestamp": 1234567890, "delay": 42, "stop_sequence": 5}

delay is in seconds (positive = late, negative = early).

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Environment variables

Variable	Example	Description
MQTT_BROKER	tcp://host.docker.internal:1883	MQTT broker URL (tcp scheme)
REDIS_URL	redis://host.docker.internal:6379/1	Redis connection URL including DB number
DATABASE_URL	postgresql+psycopg2://postgres:postgres@host.docker.internal:5432/postgres	PostgreSQL connection URL

All three are required — the service exits with KeyError if any is missing.

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Running

# Install dependencies (Python 3.13, uv)
uv sync

# Run locally (requires MQTT broker, Redis, and PostgreSQL with GTFS data)
MQTT_BROKER=tcp://localhost:1883 REDIS_URL=redis://localhost:6379/1 \
  DATABASE_URL=postgresql+psycopg2://postgres:postgres@localhost:5432/postgres \
  uv run python -m trip_updogger.main

# Build and push Docker image (requires clean, pushed branch)
make push

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Testing

# Publish a location event (vel in km/h, cog in degrees)
mosquitto_pub -t owntracks/alice/trip123 \
  -m '{"_type":"location","lat":51.5,"lon":-0.1,"tst":1700000000,"vel":36,"cog":90}'

# Verify the Redis key (use the DB set in REDIS_URL)
redis-cli -n 1 GET trip_update:trip123