Exenv

Exenv provides an adapter-based solution to loading environment variables from external sources.

It comes with the following adapter:

• Exenv.Adapters.Dotenv (load from .env files)

But has support from external adapters as well:

• Exenv.Adapters.Yaml (load from .yml files)

Installation

This package can be installed by adding exenv to your list of dependencies in mix.exs:

def deps do
  [
    {:exenv, "~> 0.3"}
  ]
end

Documentation

Please see HexDocs for additional documentation. This readme provides a brief overview, but it is recommended that the docs are used.

Getting Started

If all you want is to load a .env file on application start - then you're already done! Out of the box, Exenv is configured to start itself with the Exenv.Adapters.Dotenv adapter configured with sane defaults. This means autoloading on application start - with the .env file required to be within your projects root directory.

Configuration

If you need finer grained control of things, Exenv provides extensive config mechansims.

We can pass configuration options to Exenv from application config.

config :exenv, [
  adapters: [
    {Exenv.Adapters.Dotenv, [file: "path/to/.env"]}
  ]
]

You can also run Exenv via your own supervision tree. In this case, you must instruct Exenv not to start itself.

config :exenv, start_on_application: false

Which allows you to add Exenv to your own application.

defmodule MySupervisor do
  use Supervisor

  def start_link(opts) do
    Supervisor.start_link(__MODULE__, :ok, opts)
  end

  def init(:ok) do
    children = [
      {Exenv, [adapters: [{Exenv.Adapters.Dotenv, [file: "path/to/.env"]}]]}
    ]

    Supervisor.init(children, strategy: :one_for_one)
  end
end

Options passed to the child_spec/1 callback take precedence over any application config.

By default, all adapters will autoload their environment vars when Exenv starts up. You can override this behaviour on a per-adapter basis, by simply passing the autoload: false key within your adapter config.

[
  adapters: [
    {Exenv.Adapters.Dotenv, [autoload: false, file: "path/to/.env"]}
  ]
]

You must then manually load all env vars from your defined adapters:

Exenv.load()

Runtime path evaluation

Any location where you pass a file path you can choose to instead pass an mfa which will be run and should evaluate to a proper file path. This allows for easier runtime setup of files.

config :exenv, [
  adapters: [
    {Exenv.Adapters.Dotenv, [file: {MyApp, :get_dotenv, []}]}
  ]
]

Encryption

Exenv has secrets encryption out of the box. Support will depend on the whether the adapter provides it. Using secrets encryption allows you to keep an encrypted version of your secrets checked into your repository. As long as the master key is accessible, these secrets can then be decrypted.

To get started with secrets encryption, first generate a master key.

mix exenv.master_key /config/master.key

This will generate a new master key at /config/master.key. You can then encrypt your secrets file.

mix exenv.encrypt /config/master.key /config/.env

This will encrypt the contents of /config/.env using /config/master.key. A new file will then be generated at /config/.env.enc with your encrypted secrets.

You must then provide the proper options to your adapters to enable encryption.

{Exenv.Adapters.Dotenv, [file: "path/to/.env.enc", encryption: true]}

The above will attempt to decrypt "path/to/.env.enc" using the contents of the "MASTER_KEY" env var. Alternatively, you can also provide a direct path to the master key file.

{Exenv.Adapters.Dotenv, [file: "path/to/.env.enc", encryption: [master_key: "path/to/master.key"]]}

To edit your secrets, you just need to decrypt the original encrypted secrets, and rencrypt the edited file.

mix exenv.decrypt /config/master.key /config/.env.enc

## Add to file

mix exenv.encrypt /config/master.key /config/.env