weave

# Weave

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## A JIT configuration loader for Elixir

### About

This library makes it possible to load configuration, especially secrets, from disk (Ala Docker Swarm / Kubernetes) on start-up.

### Installation

```elixir
def deps do
  [{:weave, "~> 2.0.0"}]
end
```

### Configuration

```elixir
config :weave,
  file_directory: "path/to/secrets" # Only needed when using the File loader
  environment_prefix: "MYAPP_"      # Only needed when using the Environment loader
  handler: Your.Handler             # Always needed :smile:
```

### Manual Handler

Your handler is responsible for taking these environment variables, and/or files, and injecting their values into configuration.

`handle_configuration/2` should return a tuple with the `:app` to set the key value pair on.

Weave will handle merging, so try not to worry about that :smile:

#### Example

Lets assume:

* We are using the environment and file loaders
* We have the `environment_prefix` configured as `MY_APP_`
* We have an environment variable called `MY_APP_NAME`
* We have a file in configured secrets directory called `db_password`

Before being passed to your handler:

* All file-names and environment variables are lower-cased
* Environment variables have the prefix stripped

```elixir
defmodule Your.Handler do
  def handle_configuration("name", value) do
    {:app, :name, value}
  end

  def handle_configuration("db_password", value) do
    {:app, :password, value}
  end
end
```

#### Auto Handler Example

In-order to cut down on the boilerplate, you can use the "handler-free" approach and ensure that the values of your environment variables, or contents of files, contain:

```elixir
{:auto, :app, :name, value}
```

NB: For now, `config :weave, handler: BLAH` is still required, even if no `handle_configuration/2` functions.

### Loading Configuration

You'll need to add the following to your `start` function, before you prepare your supervisor:

```elixir
Weave.Loaders.File.load_configuration()
Weave.Loaders.Environment.load_configuration()
```

### Logging

Weave **may** log sensitive information at the `debug` level, stick to `info` in production.

### Contributing

#### Running Tests with Docker

```shell
$ docker-compose run --rm elixir
```