We use PostgreSQL to store data served on

For additional information on our architecture, see the design document.

Local development database

  1. Install PostgreSQL (version 11 or higher) on your machine for local development. It should use the default Postgres port of 5432.

    If you use a Mac, the easiest way to do that is through installing

    Another option is to use docker. The following docker command will start a server locally, publish the server's default port to the corresponding local machine port, and set a password for the default database user (named postgres).

    ./devtools/docker/ up -d db

    (NOTE: If you have already installed postgres on a workstation using sudo apt-get install postgres, you may have a server already running, and the above docker command will fail because it can't bind the port. At that point you can set GO_DISCOVERY_DATABASE_XXX environment variables to use your installed server, or stop the server using pg_ctl stop and use docker. The following assumes docker.)

    You must also install a postgres client (for example psql).

    At this point you should have a Postgres server running on your local machine at port 5432.

  2. Set the following environment variables:

    • GO_DISCOVERY_DATABASE_USER (default: postgres)
    • GO_DISCOVERY_DATABASE_HOST (default: localhost)
    • GO_DISCOVERY_DATABASE_NAME (default: discovery-db)

    See internal/config/config.go for details regarding construction of the database connection string.

    If you set up using docker in step 1, you will also need to set GO_DISCOVERY_DATABASE_PASSWORD. See setting up for tests below.

  3. Once you have Postgres installed, you should create the discovery-db database by running devtools/

    Then apply migrations, as described in ‘Migrations’ below. You will need to do this each time a new migration is added, to keep your local schema up to date.

Setting up for tests

Tests require a Postgres instance. If you followed the docker setup in step 1 in local development database above, then you have one.

When running go test ./..., database tests will not run if you don't have postgres running. To run these tests, set GO_DISCOVERY_TESTDB=true. Alternatively, you can run ./all.bash, which will run the database tests.

Tests use the following environment variables:

  • GO_DISCOVERY_DATABASE_USER (default: postgres)
  • GO_DISCOVERY_DATABASE_HOST (default: localhost)
  • GO_DISCOVERY_DATABASE_PORT (default: 5432)

If you followed the instructions for setting up with docker in step 1 of local development database above, then you only need to set GO_DISCOVERY_DATABASE_PASSWORD.

You don't need to create a database for testing; the tests will automatically create a database for each package, with the name discovery_{pkg}_test. For example, for internal/worker, tests run on the discovery_worker_test database.

If you ever run into issues with your test databases and need to reset them, you can run devtools/

Run ./all.bash to verify your setup.


Migrations are managed using, with the CLI tool.

If this is your first time using golang-migrate, check out the Getting Started guide.

To install the golang-migrate CLI, follow the instructions in the migrate CLI README.

Creating a migration

To create a new migration:

devtools/ <title>

This creates two empty files in /migrations:


The two migration files are used to migrate “up” to the specified version from the previous version, and to migrate “down” to the previous version. See golang-migrate/migrate/ for details.

If your migration requires that data be transformed, or that all modules must be reprocessed, explain in the up.sql file how to carry out the data migration.

Applying migrations for local development

Use the migrate CLI:

devtools/ [up|down|force|version] {#}

If you are migrating for the first time, choose the “up” command.

For additional details, see golang-migrate/migrate/