Hydra can be extended via plugins. The example plugins here can help you get started with plugin development.
Hydra has several plugin types:
A sweeper is responsible for converting command line arguments list into multiple jobs. For example, the basic built-in sweeper takes arguments like:
batch_size=128 optimizer=nesterov,adam learning_rate=0.01,0.1
And creates 4 jobs with the following parameters:
batch_size=128 optimizer=nesterov learning_rate=0.01batch_size=128 optimizer=nesterov learning_rate=0.1batch_size=128 optimizer=adam learning_rate=0.01batch_size=128 optimizer=adam learning_rate=0.1
Launchers are responsible for launching a job to a specific environment. A Launcher takes a batch of argument lists like the one above and launches a job for each one. The job uses those arguments to compose its configuration. The basic launcher simply launches the job locally.
A config path plugin can manipulate the search path. This can be used to influence the default Hydra configuration to be more appropriate to a specific environment, or just add new entries to the search path to make more configurations available to the Hydra app.
SearchPathPlugin plugins are discovered automatically by Hydra and are being called to manipulate the search path before the configuration is composed.
Many other plugins also implement SearchPathPlugin to add their configuration to the config search path once they are installed.
ConfigSource plugins can be used to allow Hydra to access configuration in non-standard locations when composing the config. This can be used to enable access to an in-house private config store, or as a way to access configs from public sources like GitHub or S3.