# UmbrellaStage
Subscribes GenStage consumers to producers across Elixir Umbrella apps.
## Installation
Add `umbrella_stage` to your list of dependencies in `mix.exs`:
Elixir >= 1.4 required
```elixir
def deps do
[
{:umbrella_stage, "~> 0.1.1"}
]
end
```
## Usage
1. Configuration
`use` the `UmbrellaStage` in the GenStages servers. It required 2 arguments:
- `:type` - is the GenStage type: `:producer`, `:producer_consumer` or `:consumer`
- `:producers` - required only for **consumers** and **producer_consumers**. It's the list of producers, the consumer (or producer_consumer) will subscribe to, in the following format: `{ProducerName, [subscription_options]}`
2. Call `umbrella_sync_subscribe()` in the GenStage `init`
This version of umbrella_stage implements just the [`GenStage.sync_subscribe/3`](https://hexdocs.pm/gen_stage/GenStage.html#sync_subscribe/3) subscription.
Please check [this blog post](https://medium.com/@iacobson/subscribe-genstages-under-umbrella-1fceec366633) for more details.
## Examples
A demo app is available [on GitHub](https://github.com/iacobson/blog_stockr).
### Consumer
```elixir
defmodule App1.MyConsumer do
use UmbrellaStage,
type: :consumer,
producers: [
{MyProducerConsumer, [max_demand: 10]}
]
def init() do
umbrella_sync_subscribe()
.....
end
end
```
### ProducerConsumer
```
defmodule App2.MyProducerConsumer do
use UmbrellaStage,
type: :producer_consumer,
producers: [
{MyProducer, [max_demand: 10]}
]
def init() do
umbrella_sync_subscribe()
.....
end
end
```
### Producer
```
defmodule App3.MyProducer do
use UmbrellaStage,
type: :producer
def init() do
umbrella_sync_subscribe()
.....
end
end
```