# 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)
Confex simplifies reading configuration at run-time with adapter-based system for fetch values from any source.
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, "~> 3.2.3"}]
end
2. Ensure `confex` is started before your application:
def application do
[applications: [:confex]]
end
# Usage
1. Replace values with configuration tuples
Define configuration in your `config.exs`:
config :my_app, MyApp.MyQueue,
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},
]
Configuration tuples examples:
* `var` - any bare values will be left as-is.
* `{:system, "ENV_NAME", "default"}` - read string from system environment or fallback to `"default"` if it is not set.
* `{:system, "ENV_NAME"}` - same as above, but raise error if `ENV_NAME` is not set.
Additionally you can cast string values to common types:
* `{:system, :string, "ENV_NAME", "default"}` (string is a default type).
* `{:system, :string, "ENV_NAME"}`.
* `{:system, :integer, "ENV_NAME", 123}`.
* `{:system, :integer, "ENV_NAME"}`.
* `{:system, :float, "ENV_NAME", 123.5}`.
* `{:system, :float, "ENV_NAME"}`.
* `{:system, :boolean, "ENV_NAME", true}`.
* `{:system, :boolean, "ENV_NAME"}`.
* `{:system, :atom, "ENV_NAME"}`.
* `{:system, :atom, "ENV_NAME", :default}`.
* `{:system, :module, "ENV_NAME"}`.
* `{:system, :module, "ENV_NAME", MyDefault}`.
* `{:system, :list, "ENV_NAME"}`.
* `{:system, :list, "ENV_NAME", [1, 2, 3]}`.
`:system` can be replaced with a `{:via, adapter}` tuple, where adapter is a module that implements `Confex.Adapter` behaviour.
2. Read configuration by replacing `Application.fetch_env/2`, `Application.fetch_env!/2` and `Application.get_env/3` calls with `Confex` functions
Fetch string values:
iex> Confex.fetch_env(:myapp, MyKey)
{:ok, "abc"}
Fetch integer values:
iex> Confex.fetch_env(:myapp, MyIntKey)
{:ok, 123}
Fetch configuration from maps or keywords:
iex> Confex.fetch_env(:myapp, MyIntKey)
{:ok, [a: 123, b: "abc"]}
## 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
Keyword.merge(config, Ecto.Repo.Supervisor.parse_url(url))
else
{:ok, config} = Confex.Resolver.resolve(config)
config
end
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
{:ok, config} = Confex.Resolver.resolve(config)
unless config[:secret_key_base] do
raise "Set SECRET_KEY environment variable!"
end
{:ok, config}
end
end
```
## Using Confex 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
It will add `config/0` function to `Connection` module that reads configuration at run-time for `:myapp` OTP application with key `Connection`.
You can add defaults by extending macro options:
defmodule Connection do
use Confex,
otp_app: :myapp,
some_value: {:system, "ENV_NAME", "this_will_be_default value"}
end
If application environment contains values in `Keyword` or `Map` structs, default values will be recursively merged with application configuration.
We recommend to avoid using tuples without default values in this case, since `config/0` calls will raise exceptions if they are not resolved.
You can validate configuration by overriding `validate_config!/1` function, which will receive configuration and must return it back to caller function. It will be evaluated each time `config/1` is called.
defmodule Connection do
use Confex, otp_app: :myapp
def validate_config!(config) do
unless config[:password] do
raise "Password is not set!"
end
config
end
end
# Adapters
Currently Confex supports two embedded adapters:
* `:system` - read configuration from system environment;
* `:system_file` - read file path from system environment and read configuration from this file. Useful when you want to resolve Docker, Swarm or Kubernetes secrets that are stored in files.
You can create adapter by implementing `Confex.Adapter` behaviour with your own logic.
# Helpful links
* [Docs](https://hexdocs.pm/confex)
* [REPLACE_OS_VARS in Distillery](https://hexdocs.pm/distillery/runtime-configuration.html#vm-args)
* [How to config environment variables with Elixir and Exrm](http://blog.plataformatec.com.br/2016/05/how-to-config-environment-variables-with-elixir-and-exrm/) by Platformatech.
