Switch to the MQTT-backed transport

[roata]

Currently we use an API that was not documented officially, the one that runs on top of WebSTOMP. The new API, documented in api-documentation is using MQTT and is more reliable (it runs on a separate server, and it works even when RabbitMQ is down).

The payload formats are the same, and the subscription logic is the same too.

What is different:

• what AMQP calls "routing key" is a "topic" in MQTT
• AMQP uses . separators, MQTT uses slashes /
• thus transport.telemetry.* becomes transport/telemetry/*

[iamandrewluca]

Can we get state.station from MQTT ?

For station panels we can split frontend, and use webstomp.

[roata]

Hmm, at the moment it is not available over MQTT. I will make it happen and write about it tonight.

Note, however, that this feature request is for milestone 3.0, so - in the future. At the moment our top priorities are route-multi-subscription and the performance issues #76. It is getting unusable on my phone, and sometimes even on my computer.

[roata]

@iamandrewluca, I forgot about this, but stumbled upon it today. The ETAs are now exposed to the public via MQTT as well, here's how it works: mosquitto_sub -h opendata.dekart.com -p 1945 -t state/infopanel/+

Payload example:

{"route": 30, "station": "Aeroport - pornire", "time": "2"}

• the MQTT topic will contain the bus station ID (we'll have to make a dictionary of those, like in vehicles.csv and routes.csv)
• route - human-readable route name (not route_upstream_id! - this might have to be reconsidered), the ETA for which is sent
• station - human readable name of the station, might be removed in the future, once we have a dictionary of station IDs and names
• time - the time, in minutes, until the next vehicle of the given route will arrive to this station.

The format is a draft and will be changed, based on feedback. The payloads may contain other elements - don't count on those.

[roata]

This could be relevant, since the bus telemetry also uses MQTT: roataway/gtfs-data#5

[iamandrewluca]

Notes;

• https://github.com/roataway/examples/tree/master/javascript-websocket-leaflet