Hacking

This section provides some notes on how to hack on Hydra. To get the latest version of Hydra from GitHub:

$ git clone git://github.com/NixOS/hydra.git
$ cd hydra

To enter a shell in which all environment variables (such as PERL5LIB) and dependencies can be found:

$ nix develop

To build Hydra, you should then do:

$ mesonConfigurePhase
$ ninja

You start a local database, the webserver, and other components with foreman:

$ foreman start

The Hydra interface will be available on port 63333, with an admin user named “alice” with password “foobar”

You can run just the Hydra web server in your source tree as follows:

$ ./src/script/hydra-server

You can run Hydra’s test suite with the following:

$ meson test
# to run as many tests as you have cores:
$ YATH_JOB_COUNT=$NIX_BUILD_CORES meson test

To run individual tests:

# Run a specific test file
$ PERL5LIB=t/lib:$PERL5LIB perl t/test.pl t/Hydra/Controller/API/checks.t

# Run all tests in a directory
$ PERL5LIB=t/lib:$PERL5LIB perl t/test.pl t/Hydra/Controller/API/

Warning: Currently, the tests can fail if run with high parallelism due to an issue in Test::PostgreSQL causing database ports to collide.

Working on the Manual

By default, foreman start runs mdbook in “watch” mode. mdbook listens at http://localhost:63332/, and will reload the page every time you save.

Building

To build Hydra and its dependencies:

$ nix build .#packages.x86_64-linux.default

Development Tasks

Connecting to the database

Assuming you’re running the default configuration with foreman start, open an interactive session with Postgres via:

$ psql -h localhost -p 64444 hydra

Running the builder locally

To build and test the queue-runner:

$ cargo build -p hydra-queue-runner
$ cargo test -p hydra-queue-runner

foreman start launches the queue-runner automatically with the right config and environment. If a previous instance crashed, you may need to remove the stale lock file:

$ rm .hydra-data/queue-runner/lock

For hydra-queue-runner to successfully build locally, your development user will need to be “trusted” by your Nix store.

Add yourself to the trusted_users option of /etc/nix/nix.conf.

On NixOS:

{
  nix.settings.trusted-users = [ "YOURUSER" ];
}

Off NixOS, change /etc/nix/nix.conf:

trusted-users = root YOURUSERNAME