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Version: 1.3

In Hydra 1.0, when a config file is loaded, if a config with a matching name and group is present in the ConfigStore, it is used as the schema for the newly loaded config.

There are several problems with this approach:

  • Inflexible: This approach can only be used when a schema should validate a single config file. It does not work if you want to use the same schema to validate multiple config files.
  • Unexpected: This behavior can be unexpected. There is no way to tell this is going to happen when looking at a given config file.

Hydra 1.1 deprecates this behavior in favor of an explicit config extension via the Defaults List.
This upgrade page aims to provide a summary of the required changes. It is highly recommended that you read the following pages:

Migration​

Before the upgrade, you have two different configs with the same name (a config file, and a Structured Config in the ConfigStore). You need to rename one of them. Depending on the circumstances and your preference you may rename one or the other.

  • If you control both configs, you can rename either of them.
  • If you only control the config file, rename it.

Option 1: rename the Structured Config​

This option is less disruptive. Use it if you control the Structured Config.

  1. Use a different name when storing the schema into the Config Store. Common choices:
    • base_ prefix, e.g. base_mysql.
    • _schema suffix, e.g. mysql_schema.
  2. Add the schema to the Defaults List of the extending config file.
Click to show an example

Hydra 1.0​

db/mysql.yaml
# @package _group_
host: localhost
port: 3306






db/mysql schema in the ConfigStore
@dataclass
class MySQLConfig:
    host: str
    port: int

cs = ConfigStore.instance()
cs.store(group="db",
         name="mysql", 
         node=MySQLConfig)

Hydra 1.1​

db/mysql.yaml
defaults:
  - base_mysql

host: localhost
port: 3306




db/mysql schema in the ConfigStore
@dataclass
class MySQLConfig:
    host: str
    port: int

cs = ConfigStore.instance()
cs.store(group="db",
         name="base_mysql", 
         node=MySQLConfig)

Option 2: rename the config file​

This option is a bit more disruptive. Use it if you only control the config file.

  1. Rename the config file. Common choices are custom_ or my_ prefix, e.g. custom_mysql.yaml. You can also use a domain specific name like prod_mysql.yaml.
  2. Add the schema to the Defaults List of the extending config file.
  3. Update references to the config name accordingly, e.g. on the command-line db=mysql would become db=custom_mysql, and in a defaults list db: mysql would become db: custom_mysql.
Click to show an example

Hydra 1.0​

db/mysql.yaml
# @package _group_
host: localhost
port: 3306
config.yaml
defaults:
  - db: mysql
db/mysql schema in the ConfigStore
@dataclass
class MySQLConfig:
    host: str
    port: int

cs = ConfigStore.instance()
cs.store(group="db",
         name="mysql", 
         node=MySQLConfig)

Hydra 1.1​

Rename db/mysql.yaml to db/custom_mysql.yaml and explicitly add the schema to the Defaults List.

db/custom_mysql.yaml
defaults:
  - mysql

host: localhost
port: 3306
config.yaml
defaults:
  - db: custom_mysql
db/mysql schema in the ConfigStore





                   NO CHANGES






Don't forget to also update your command line overrides from db=mysql to db=custom_mysql.