# `FlamePeer`
[🔗](https://github.com/probably-not/flame-peer/blob/v1.0.2/lib/flame_peer.ex#L1)

`FlamePeer` provides a FLAME backend for Erlang `:peer` nodes.

## How Does It Work?

`FlamePeer` uses Erlang's `:peer` module in order to create `:peer` nodes.
This backend can be used to mimic a realistic FLAME cluster with real, isolated nodes that run on the local machine.
It should generally be reserved for running in test and development environments to fully mimic the FLAME experience while staying fully local.

## Usage

To use, you must tell FLAME to use the `FlamePeer` backend by default.
This can be set via application configuration in your `config/dev.exs` and `config/test.exs`:

```elixir
config :flame, :backend, FlamePeer
```

### Required Configurations

* `:app` - The name of your application. Defaults to `System.get_env("RELEASE_NAME")` in a release. However, since this backend is typically
used in development and testing environments, it must be set on the configuration.

### Optional Configurations

* `:boot_timeout` - A timeout for booting a new node. Defaults to 30_000 (30 seconds).

* `:peer_applications` - A list of peer applications to enforce starting on the peer node.
Erlang `:peer` nodes don't automatically start any applications on startup, so this configuration defines which applications
should be initialized on startup. Defaults to the `:app` value. If your application needs other applications to start up automatically,
they must be specified in this option. The `:flame` and `:flame_peer` applications are automatically enforced to be in this list, to ensure
that the necessary processes for FLAME and FlamePeer are properly started at all times.

## Environment Variables

`:peer` nodes *do not* inherit the environment variables of the parent.
You must explicit provide the environment that you would like to forward to the
machine. For example, if your FLAME's are starting your Ecto repos, you can copy
the env from the parent:

```elixir
config :flame, FlamePeer,
  env: %{
    "DATABASE_URL" => System.fetch_env!("DATABASE_URL"),
    "POOL_SIZE" => "1"
  }
```

Or pass the env to each pool:

```elixir
{FLAME.Pool,
  name: MyRunner,
  backend: {FlamePeer, env: %{"DATABASE_URL" => System.fetch_env!("DATABASE_URL")}}
}
```