Dotenvy

Dotenvy is an Elixir implementation of the original dotenv Reby gem, compatible with mix and releases. It is designed to help the development of applications following the principles of the 12-factor app and its recommendation to store configuration in the environment.

Installation

Add dotenvy to your list of dependencies in mix.exs:

def deps do
  [
    {:dotenvy, "~> 0.1.0"}
  ]
end

It has no dependencies.

Usage

Dotenvy is designed to help configure your application at runtime, and one of the most effective places to do that is inside config/runtime.exs (available since Elixir v1.11).

The Dotenvy.source/2 function can accept a list of paths of where to look for dotenv files -- when combined with Config.config_env/0 it is easy to load up environment-specifc config, e.g.

source([".env", ".env.\#{config_env()}", ".env.\#{config_env()}.local"])

By default, the listed files do not need to exist -- if no file exists at the specified path, the next path is tried. This makes it easy to commit basic files for default values and basic funcitonality, and still leave the door open to developers so they can override them with their own configurations.

For a simple exmample, we can load a single file:

# config/runtime.exs
import Config
import Dotenvy

source!(".env")

config :myapp, MyApp.Repo,
    database: env!("DATABASE", :string!),
    username: env!("USERNAME", :string),
    password: env!("PASSWORD", :string),
    hostname: env!("HOSTNAME", :string!),
    pool_size: env!("POOL_SIZE", :integer),
    adapter: env("ADAPTER", :module, Ecto.Adapters.Postgres),
    pool: env!("POOL", :module?)

And then define your variables in the file(s) to be sourced. Dotenvy has no opinions about what you name your files; .env is merely a convention.

# .env
DATABASE=myapp_dev
USERNAME=myuser
PASSWORD=mypassword
HOSTNAME=localhost
POOL_SIZE=10
POOL=

When you set up your application configuration in this way, you are creating a contract with the environment (errors will be raised if certain system variables are not set), and this is an approach that works equally well for your day-to-day development and testing, as well as for mix releases.

Read the configuration strategies for other more detailed examples of how to configure your app.

Refer to the "dotenv" (.env) file format for more examples and features of the supported syntax.

See the Dotenvy module documentation on its functions.

Note for Mix Tasks

If you have authored your own Mix tasks, you must ensure that they load the application configuration in a way that is compatible with the runtime config. A good way to do this is to include Mix.Task.run("app.config") inside the run/1 implementation, e.g.

def run(_args) do
  Mix.Task.run("app.config")
  # ...
end

Image Attribution: "dot" by Stepan Voevodin from the Noun Project