Hush

Hush makes it easy to configure your application at runtime and in release mode, it can retrieve configuration from multiple sources and is easily extensible.

You'd use Hush as a configuration tuple, which gets replaced at runtime, this is useful to inject configuration that is not known at compile time.

# config/prod.exs
alias Hush.Provider.{GcpSecretManager,SystemEnvironment}

config :your_app_name, Web.Endpoint,
  http: [port: {:hush, SystemEnvironment, "PORT", [cast: :integer]}]
  secret_key_base: {:hush, GcpSecretManager, "secret_key_base"}

Hush ships with a SystemEnvironment provider which reads environmental variables, but multiple providers exist to make your life easy in reading from other sources:

Provider	Description
`SystemEnvironment`	Read environmental variables
`GcpSecretManager`	Load secrets from Google Cloud Platform's Secret Manager.

Installation

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

def deps do
  [
    {:hush, "~> 0.0.4"}
  ]
end

Run mix deps.get to install it.

Configuration

Some providers may need to initialize applications to function correctly. SystemEnvironment does not require any initialization and does not need to be in the list below.

# config/config.exs

config :hush,
  providers: [
    GcpSecretsManager
  ]

Resolving Runtime Configuration

Hush can be loaded by calling it directly, or by using its release Config.Provider.

Loading via direct call

# application.ex

def start(_type, _args) do
  Hush.resolve!()
end

Loading via Config Provider

# mix.exs
def project do
  [
    # ...
    releases: [
      your_app_name: [
        config_providers: [{Hush.ConfigProvider, nil}]
      ]
    ]
  ]
  end

If you are using Hush in both release and non-release mode, you still want to load it directly:

# application.ex

def start(_, _) do
  unless Hush.release_mode?(), do: Hush.resolve!()
end

Usage

The configuration tuple is defined by a :hush atom, a provider module, a key for the provider and an optional list of options.

{
  :hush,
  provider :: module(),
  key :: String.t(),
  options :: [
    default: any(),
    cast: :string | :integer | :float | :charlist | :atom
  ]
}

Defaults

By default if a given key is not found by the provider, Hush will raise an error. To prevent this, provide a default in the options component of the tuple:

# config/prod.exs
alias Hush.Provider.SystemEnvironment

config :your_app_name, Web.Endpoint,
  url: [host: {:hush, SystemEnvironment, "HOST", [default: "my-app.example"]}]

Casting

# config/prod.exs
alias Hush.Provider.SystemEnvironment

config :your_app_name, Web.Endpoint,
  http: [port: {:hush, SystemEnvironment, "PORT", [cast: :integer, default: 4000]}]

License

Hush is released under the Apache License 2.0 - see the LICENSE file.

v0.0.4