# Confex
[](https://beta.hexfaktor.org/github/Nebo15/confex) [](https://hex.pm/packages/confex) [](https://hex.pm/packages/confex) [](https://hex.pm/packages/confex) [](https://travis-ci.org/Nebo15/confex) [](https://coveralls.io/github/Nebo15/confex?branch=master) [](https://ebertapp.io/github/Nebo15/confex)
This is helper module that provides a nice way to read environment configuration at runtime. It's inspired by Phoenix `{:system, value}` definition for HTTP port.
## Installation
It's available on [hex.pm](https://hex.pm/packages/confex) and can be installed as project dependency:
1. Add `confex` to your list of dependencies in `mix.exs`:
def deps do
[{:confex, "~> 2.0.0"}]
end
2. Ensure `confex` is started before your application:
def application do
[applications: [:confex]]
end
# Usage
1. Defining configurations
Define your configuration in config.ex of your application.
config :ap_cfpredictor, AssetProcessor.AMQP.Producer,
queue: [
name: {:system, "OUT_QUEUE_NAME", "MyQueueOut"},
error_name: {:system, "OUT_ERROR_QUEUE_NAME", "MyQueueOut.Errors"},
routing_key: {:system, "OUT_ROUTING_KEY", ""},
durable: {:system, "OUT_DURABLE", false},
port: {:system, :integer, "OUT_PORT", 1234},
],
List of supported formats:
* `var` - any bare values will be left as-is.
* `{:system, "ENV_NAME", default}` - read string from system ENV, return `default` if it's nil.
* `{:system, "ENV_NAME"}` - read string from system ENV, returns `nil` if environment variables doesn't exist.
* `{:system, :string, "ENV_NAME", default}` - same as `{:system, "ENV_NAME", default}`.
* `{:system, :string, "ENV_NAME"}` - same as `{:system, "ENV_NAME"}`.
* `{:system, :integer, "ENV_NAME", default}` - same as `{:system, "ENV_NAME", default}`, but will convert value to integer if it's not `nil`. Default value type **will not** be changed.
* `{:system, :integer, "ENV_NAME"}` - same as `{:system, :integer, "ENV_NAME", nil}`.
* `{:system, :boolean, "ENV_NAME", default}` - same as `{:system, "ENV_NAME", default}`, but will convert value to boolean if it's not `nil`. Default value type **will not** be changed.
* `{:system, :boolean, "ENV_NAME"}` - same as `{:system, :boolean, "ENV_NAME", nil}`.
* `{:system, :atom, "ENV_NAME"}`
* `{:system, :atom, "ENV_NAME", :default}`
* `{:system, :module, "ENV_NAME"}`
* `{:system, :module, "ENV_NAME", Default}`
* `{:system, :list, "ENV_NAME"}` - same as `{:system, :list, "ENV_NAME", nil}`.
* `{:system, :list, "ENV_NAME", Default}` - same as `{:system, "ENV_NAME", default}`, but will convert value to list if it's not `nil`, splitting at commas. Default value type **will not** be changed.
2. Reading configuration
Read string values:
iex> Confex.get(:myapp, MyKey)
"abc"
Read integer values:
Confex.get(:myapp, MyIntKey)
123
Read map values:
Confex.get_map(:myapp, MyIntKey)
[a: 123, b: "abc"]
3. Using macros
Confex is supplied with helper macros that allow to attach configuration to specific modules of your application.
defmodule Connection do
use Confex, otp_app: :myapp
end
`Connection` in this case will read configuration from app `:myapp` with key `Connection`. Also it will provide helper function `config/0` that will return values at run-time.
4. Configuration validation
Sometimes you want to validate configuration, for this you can define `def validate_config(config)` method, that will be called on each `config/0` usage.
Confex doesn't give opinions on a validator to be used in overrided methods.
## Integrating with Ecto
Ecto has a `init/2` callback, you can use it with Confex to read environment variables. We used to have all our repos to look like this:
```elixir
defmodule MyApp do
use Ecto.Repo, otp_app: :my_app
@doc """
Dynamically loads the repository configuration from the environment variables.
"""
def init(_, config) do
url = System.get_env("DATABASE_URL")
config = if url, do: Ecto.Repo.Supervisor.parse_url(url), else: Confex.process_env(config)
unless config[:database] do
raise "Set DB_NAME environment variable!"
end
unless config[:username] do
raise "Set DB_USER environment variable!"
end
unless config[:password] do
raise "Set DB_PASSWORD environment variable!"
end
unless config[:hostname] do
raise "Set DB_HOST environment variable!"
end
unless config[:port] do
raise "Set DB_PORT environment variable!"
end
{:ok, config}
end
end
```
## Integrating with Phoenix
1. Set `on_init` callback in your `prod.exs`:
```elixir
config :my_app, MyApp.Web.Endpoint,
on_init: {MyApp.Web.Endpoint, :load_from_system_env, []}
```
2. Add `load_from_system_env` function to your endpoint:
```elixir
defmodule Mithril.Web.Endpoint do
# Some code here
@doc """
Dynamically loads configuration from the system environment
on startup.
It receives the endpoint configuration from the config files
and must return the updated configuration.
"""
def load_from_system_env(config) do
config = Confex.process_env(config)
unless config[:secret_key_base] do
raise "Set SECRET_KEY environment variable!"
end
{:ok, config}
end
end
```
# Configuration priorities
By using Confex macro in your module, you allow to provide compile-time defaults for it.
1. Declare module
defmodule MyModule do
use Confex
end
2. Provide defaults when using it
use MyModule,
otp_all: :myapp,
host: {:system, "HOST"}
This configs will overwritten by any configuration that you have in your application env.
# Helpful links
* [Docs](https://hexdocs.pm/confex)
