Consume GTFS-RT Vehicle Positions, introduce API

[leonardehrenfried]

Summary

This PR adds a graph updater that downloads GTFS-RT Vehicle Position feeds. It keeps an internal data model and accounting for them and adds the entities to the legacy graphql API.

This is a port of what IBI added to their 1.5 fork last year: ibi-group#63

The main difference is that the positions are not added directly to the TripPattern instances but they are stored in a separate service just as the realtime alerts are.

Configuration

To use it add the following to router-config.json

{
  "updaters": [
    {
      "type": "vehicle-positions",
      "sourceType": "gtfs-http",
      "url": "https://s3.amazonaws.com/kcm-alerts-realtime-prod/vehiclepositions.pb",
      "feedId": "1",
      "frequencySec": 59
    }
  ]
}

You can query them in the legacy GraphQL API like this:

query {
	patterns {
		route {
			gtfsId
			shortName
		}
		code
		vehiclePositions {
			vehicleId
			lat
			lon
			vehicleId
			stopRelationship {
				status
				stop {
					name
				}
			}
			lastUpdated
			trip {
				gtfsId
				tripHeadsign
			}
		}
	}
}

Future work

This solution provides an easy to consume API for drawing a couple of dozen vehicles on a map, but is not really suitable for fetching a large number of quickly updating positions. For such a system a streaming approach (MQTT, websockets, ...) would superior. Once IBI has streaming data sources and the need to draw a large number of updates on a screen, they might contribute a solution for this.

Unit tests

Both the parser and the matcher/service have tests.

Code style

Yes.

Documentation

Yes.

/cc @miles-grant-ibigroup @demory

[optionsome]

This is undoing @t2gran work on the data fetchers. I guess it's better to use the version that is automatically generated instead of always rerunning the intellij refactor thingy?

[leonardehrenfried]

This is undoing @t2gran work on the data fetchers. I guess it's better to use the version that is automatically generated instead of always rerunning the intellij refactor thingy?

Yes, after you left we decided the following: we will keep the public but Hannes will look into modifying the generator so that this is no longer emitted.