Config Store API

Throughout the rest of tutorials, we will be using ConfigStore to register dataclasses as input configs in Hydra. ConfigStore is a singleton storing configs in memory. The primary API for interacting with the ConfigStore is the store method described below.

API

class ConfigStore(metaclass=Singleton):
    def store(
        self,
        name: str,
        node: Any,
        group: Optional[str] = None,
        package: Optional[str] = "_group_",
        provider: Optional[str] = None,
    ) -> None:
        """
        Stores a config node into the repository
        :param name: config name
        :param node: config node, can be DictConfig, ListConfig,
            Structured configs and even dict and list
        :param group: config group, subgroup separator is '/',
            for example hydra/launcher
        :param package: Config node parent hierarchy.
            Child separator is '.', for example foo.bar.baz
        :param provider: the name of the module/app providing this config.
            Helps debugging.
        """
    ...

ConfigStore and YAML input configs

ConfigStore has feature parity with YAML input configs. On top of that, it also provides typing validation. ConfigStore can be used alone or together with YAML. We will see more examples later in this series of tutorials. For now, let's see how the ConfigStore API translates into the YAML input configs, which we've become more familiar with after the basic tutorials.

Say we have a simple application and a db config group with a mysql option:

my_app.py

@hydra.main(version_base=None, config_path="conf")
def my_app(cfg: DictConfig) -> None:
    print(OmegaConf.to_yaml(cfg))


if __name__ == "__main__":
    my_app()

Directory layout

├─ conf
│  └─ db
│      └─ mysql.yaml
└── my_app.py

db/mysql.yaml

driver: mysql
user: omry
password: secret

What if we want to add an postgresql option now? Yes, we can easily add a db/postgresql.yaml config group option. But that is not the only way! We can also use ConfigStore to make another config group option for db available to Hydra.

To achieve this, we add a few lines (highlighted) in the above my_app.py file:

my_app.py

@dataclass
class PostgresSQLConfig:
    driver: str = "postgresql"
    user: str = "jieru"
    password: str = "secret"

cs = ConfigStore.instance()
# Registering the Config class with the name `postgresql` with the config group `db`
cs.store(name="postgresql", group="db", node=PostgresSQLConfig)

@hydra.main(version_base=None, config_path="conf")
def my_app(cfg: DictConfig) -> None:
    print(OmegaConf.to_yaml(cfg))


if __name__ == "__main__":
    my_app()

Now that our application has access to both db config group options, let's run the application to verify:

python my_app.py +db=mysql

db:
  driver: mysql
  user: omry
  password: secret

python my_app.py +db=postgresql

db:
  driver: postgresql
  user: jieru
  password: secret

Example node values

A few examples of supported node values parameters:

from dataclasses import dataclass

from hydra.core.config_store import ConfigStore

@dataclass
class MySQLConfig:
    host: str = "localhost"
    port: int = 3306

cs = ConfigStore.instance()

# Using the type
cs.store(name="config1", node=MySQLConfig)
# Using an instance, overriding some default values
cs.store(name="config2", node=MySQLConfig(host="test.db", port=3307))
# Using a dictionary, forfeiting runtime type safety
cs.store(name="config3", node={"host": "localhost", "port": 3308})