# Weave
**Note:** The canonical repository is hosted [here](https://gitlab.com/gt8/open-source/elixir/weave), on GitLab.com.
[](https://hex.pm/packages/weave)
[](https://hex.pm/packages/weave)
[](https://hex.pm/packages/weave)
[](https://gitlab.com/gt8/open-source/elixir/weave/commits/master)
[](https://gitlab.com/gt8/open-source/elixir/weave/commits/master)
## 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.
#### Icon
“To Weave” icon by Amrit Mazumder from the Noun Project.
### Installation
```elixir
def deps do
[{:weave, "~> 4.0.0"}]
end
```
### Weave Module
In order to transform environment variables, or file contents, to runtime configuration, you must tell Weave how to handle those values.
You do this by creating a Weave module, such as:
```elixir
defmodule MyApp.Weave do
use Weave
weave "some_environment_var_without_the_prefix",
required: false, # required: can be omitted and defaults to false
handler: {:myapp, :some_key}, # handler: can be a function, list or tuple
handler: [{:myapp, :some_key}, {:myapp, :another_key}],
handler: fn(value) -> Logger.configure(value) end)
end
```
#### 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 MyApp.Weave do
use Weave
weave "name", handler: {:app, :name}
weave "db_password", required: true, handler: {:app, :password}
# Sometimes you need to use the same value twice, so return a list.
weave "kafka_host", handler: [
{:kaffe, :consumer},
{:kaffe, :producer}
]
end
```
#### Auto Handler Example
##### Warning: We intially thought this would help you reduce all the boilerplate associated with writing handlers. We're now not sure this is really worth it. Use with caution.
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}
```
### Loading Configuration
You'll need to add the following to your `configure` function, before you prepare your supervisor:
```elixir
MyApp.Weave.configure([
only: ["database_password", "database_username", "database_host"],
loaders: [
{Weave.Loaders.Environment, [prefix: "MYAPP_"]},
{Weave.Loaders.File, [directories: [
"/run/secrets",
"/etc/config/my_app"
]]}
]
])
```
### Logging
Weave **may** log sensitive information at the `debug` level, stick to `info` in production.
#### Running Tests with Docker
```shell
$ make clean deps test
```
