Transiter

Transiter is a backend web service that makes it easy to use realtime transit data. Transiter can be used to build things like web apps (realtimerail.nyc, closingdoors.nyc) and arrival time boards, and query transit data from other applications.

Transiter subscribes to GTFS transit data feeds from different transit agencies and provides integrated views of the data through a HTTP REST API. The endpoint for each station, for example, provides:

• the station's static data (such as its name and GPS coordinates),

• the station's realtime data (the list of vehicles that will arrive next, and the times they will arrive),

• and derived data that Transiter computes automatically, such as which routes usually call at the station.

You can get a sense for the data that's available by navigating through the live demo site, or by interacting with it programmatically:

# Python snippet that finds the next train at the Rockefeller Center NYC subway station
import requests, time
data = requests.get("https://demo.transiter.dev/systems/us-ny-subway/stops/D15").json()
firstStopTime = data["stopTimes"][0]
secondsToLeave = int(firstStopTime["departure"]["time"]) - time.time()
print(f'The next train leaves in {int(secondsToLeave)} seconds and goes to {firstStopTime["trip"]["destination"]["name"]}.')

The beginner's guide contains many more examples of data that's available from the API.

Note that the demo site is best effort! In general if you want to use Transiter for an application you will run and own your own Transiter deployment.

Quickstart guide

This is a whirlwind version of the beginner's guide on the documentation website.

Transiter uses Postgres for persisting data, and requires Postgres to have the PostGIS Postgres extension By default Transiter assumes the database/user/password is transiter/transiter/transiter, but all these values can be configured. If you have Docker installed, you can easily spin up the right kind of Postgres instance by running the following command:

docker run \
    -e POSTGRES_USER=transiter -e POSTGRES_PASSWORD=transiter -e POSTGRES_DB=transiter \
    -p 0.0.0.0:5432:5432 \
    postgis/postgis:14-3.4

Next you need to install Transiter, which is distributed both as a single standalone binary or a Docker image. There are few options for installing Transiter:

• Prebuilt binaries are available on the GitHub releases page.
• If you have Go installed, you can simply run go install . in the root of the Transiter repo.
• Run Transiter using Docker - replace transiter with docker run --network=host jamespfennell/transiter:latest in the examples below.

After installation, the Transiter server is launched using:

transiter server --log-level debug

Transiter's HTTP API will now be available on localhost:8080. In addition to the HTTP API, you can interact with the server using Transiter client commands. For example to list all installed transit system run:

transiter list

This will show that there are no transit systems installed. The next step is install one!

San Francisco area BART:

transiter install us-ca-bart

New York City subway:

transiter install us-ny-subway

In either case, the server logs will show GTFS feed updates happening every few seconds, and the HTTP API will be populated with data. If you installed the BART, you can get data about the Embarcadero station by visiting:

localhost:8080/systems/us-ca-bart/stops/place_EMBR

Development guide

This is a guide for developing Transiter itself. PRs are very welcome!

Dev requirements

The basic requirements are the same as for running Transiter, Postgres 14+ with PostGIS and Go 1.18+. Additionally, the project uses the command runner tool Just. Installing Just is optional: as an alternative, you can always manually run the commands in the justfile. However we think Just is great, and the rest of this guide assumes you've installed it. Finally, having Docker available makes it really easy to run some other things locally but is totally optional.

Changing the code

If you just change the Go code, you can build the code using go build . and run all the unit tests using go test ./... or just test. Note that the unit tests assume Postgres is up and use Postgres for a bunch of DB tests.

If you have Docker installed you can also run all the Python E2E tests by running just test-e2e. (The command just test-all runs both the unit and E2E tests). The E2E tests are in the tests/endtoend directory. Without Docker it's still possible to run the E2E tests following the instructions in that directory. However the E2E tests also run on the GitHub actions CI and it's perhaps easiest to rely on that. The E2E tests generally don't break unless you've introduced a regression. For new major features it's great to add new E2E tests.

Like many Go projects Transiter relies on some code generation:

• Transiter uses sqlc for generating all of the DB interaction code. The DB schema and queries are stored in the db directory.

• Transiter uses gRPC for developing the API. The HTTP REST API is generated automatically using annotations in the proto files. Buf is used for compiling the proto files to the Go code.

If you make any changes to the API (.proto files) or DB SQL statements (.sql files), you'll need to run the code generation tools.

First install the tools:

just install-tools

Then run the code generation:

just generate

Creating a release

Releases are created in the GitHub UI. The release number vX.Y.Z must match the contents of the file internal/version/BASE_VERSION. In the releases UI:

• Use a new tag with name vX.Y.Z.
• Set the release name to vX.Y.Z.
• Mark the release as a pre-release. The goreleaser infrastructure will automatically promote it to a full release when the assets are pushed.

After the release is created, bump the version number in internal/version/BASE_VERSION and commit to mainline.

License

MIT