# Galena

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Galena is a topic producer-consumer library built on top of [GenStage]( for [Elixir]( 

I highly recommend to initiate your producers/consumers under a [Supervisor](

## Installation

If [available in Hex](, the package can be installed as:

  * Add `galena` to your list of dependencies in `mix.exs`:

    def deps do
       [{:galena, "~> 0.1.2"}]
## Definition
  * Define your Producer(s). Your producer could be connected to external system like RabbitMQ, Kafka, DataBases, ...
   Code the function handle_produce(data), where data can be whatever, and
   has to return a tuple where the first value has to be a topic and the second one the message. 
   To guarantee a good performance, try to optimize as much as possible this function.
  defmodule MyProducer do
    use Galena.Producer

    def handle_produce({topic, data}) do
      {topic, data}
  * Define your Producer-Consumer(s). A Producer-Consumer will have the functionalities of 
  a consumer and a producer. It needs an implementation close to a producer (handle_produce(topic, data))
  and the initialization of a consumer.
  defmodule MyProducerConsumer do
    use Galena.ProducerConsumer
    def handle_produce(topic, data) do
      result_topic = topic <> Integer.to_string(:rand.uniform(2))
      {result_topic, "modified by producer-consumer: " <> data}
  * Define and run your Consumer. Code the function handle_consume(topic, message).
  A consumer could be subscribed to different topics of the
  same producer or even to different producers. We have to indicate it using a Keyword list as first
  parameter which has to contain the information about the producers.
  # Example
  args = [
    producers_info: [
      {["topic_1", "topic_2", "topic_3"], :producer1},
      {["topic_A"], :producer2},
      {["topic_a", "topic_b"], :producer3},
      {[], :producer4}
  defmodule MyConsumer do
    use Galena.Consumer
    def handle_consume(topic, message) do
      IO.puts(topic <> ": " <> message)

## Running

  * Run and begin to ingest data
  # One producer
  iex> MyProducer.start_link([], [name: :producer])
  # One producer-consumer
  iex> MyProducerConsumer.start_link([producers_info: [{["topic"], :producer}]], [name: :prod_cons])
  # Two consumers
  iex> MyConsumer.start_link([producers_info: [{["topic1"], :prod_cons}]], [name: :consumer1])
  iex> MyConsumer.start_link([producers_info: [{["topic2"], :prod_cons}]], [name: :consumer2])
  # Data ingestion
  iex> for i <- 1..100, do: MyProducer.ingest(:producer, {"topic", "Hola" <> Integer.to_string(:rand.uniform(100))})

## Test
  * Run the tests.
  mix test