ConfigTuples provides a distillery's config provider that replace config tuples (e.g {:system, value}) to their expected runtime value.

Documentation can be found at https://hexdocs.pm/config_tuples.

Add the package by adding config_tuples to your list of dependencies in mix.exs:

def deps do
  [
    {:config_tuples, "~> 0.2.0"}
  ]
end

Then, add it to the config providers of distillery in rel/config.exs

release :myapp do
  # ...snip...
  set config_providers: [
    ConfigTuples.Provider
  ]
end

This will result in ConfigTuples.Provider being invoked during boot, at which point it will evaluate the current configuration for all the apps and replace the config tuples when needed, persisting it in the configuration.

The config tuple always start with :system, and can have some options as keyword, the syntax are like this:

• {:system, env_name}
• {:system, env_name, opts}

The available options are:

• type: Type to cast the value, one of :string, :integer, :atom, :boolean. Default to :string
• default: Default value if the environment variable is not setted. Default no nil
• transform: Function to transform the final value, the syntax is {Module, :function}

If you need to store the literal values {:system, term()}, {:system, term(), Keyword.t()}, you can use {:system, :literal, term()} to disable ConfigTuples config interpolation. For example:

# This will store the value {:system, :foo}
config :my_app,
  value: {:system, :literal, {:system, :foo}}

This could be an example for Ecto repository and logger:

config :my_app,
  uri: {:system, "HOST", transform: {MyApp.UriParser, :parse}}

config :my_app, MyApp.Repo,
  adapter: Ecto.Adapters.MySQL,
  username: {:system, "DATABASE_USERNAME", default: "root"},
  password: {:system, "DATABASE_PASSWORD", default: "toor"},
  database: {:system, "DATABASE_DB", default: "myapp"},
  hostname: {:system, "DATABASE_HOST", default: "localhost"},
  port: {:system, "DATABASE_PORT", type: :integer, default: 3306},
  pool_size: {:system, "DATABASE_POOL_SIZE", type: :integer, default: 10}

config :logger,
  level: {:system, "LOG_LEVEL", type: :atom, default: :info}