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-shell

of when flakes are enabled:

$ nix develop

To build Hydra, you should then do:

[nix-shell]$ autoreconfPhase
[nix-shell]$ configurePhase
[nix-shell]$ make -j$(nproc)

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:

[nix-shell]$ make check
[nix-shell]$ # to run as many tests as you have cores:
[nix-shell]$ make check YATH_JOB_COUNT=$NIX_BUILD_CORES
[nix-shell]$ # or run yath directly:
[nix-shell]$ yath test
[nix-shell]$ # to run as many tests as you have cores:
[nix-shell]$ yath test -j $NIX_BUILD_CORES

When using yath instead of make check, ensure you have run make in the root of the repository at least once.

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 release.nix -A build.x86_64-linux

Development Tasks

Connecting to the database

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

$ psql --host localhost --port 64444 hydra

Runinng the builder locally

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

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