Herald

Herald is a library to exchange async messages between systems through a message broker.

These library support AMQP based message brokers

Installation

Add in your mix.exs and run mix deps.get:

def deps do
  [
    {:herald, "~> 0.1.0"}
  ]
end

Getting start

Subscriptions

1. Create you message schema:

defmodule MyApp.Message do
  use Herald.Message

  payload do
    field :age,  :integer
    field :name, :string, required: true
  end
end

2. Create your processor function

Processor function will work as a callback function when a message is received.

defmodule MyApp.Message do
  use Herald.Message

  payload do
    field :age,  :integer
    field :name, :string, required: true
  end

  def my_processor(%MyApp.Message{} = message) do
    if do_some_stuff_with(message) do
      {:ok, message}
    else
      {:error, :my_bad_error}
    end
  end
end

3. Create your Router

Router will say for library what schema and processor use for each queue.

In example bellow, any message received in queue my_queue will be validated by schema MyApp.Message, and processed by function &MyApp.Message.my_processor/1.

defmodule MyApp.Router do
  use Herald.Router

  route "my_queue",
    schema: MyApp.Message,
    processor: &MyApp.Message.my_processor/1
end

4. Configure this

Finaly, need inform Herald what is the module where router is configured:

config :herald,
  router: Develop.Router

Publishing

Publications can be performed as bellow:

alias Herald.AMQP.Publisher

MyApp.Message.new("queue", %{
  "age"  => 70,
  "name" => "Dennis Ritchie"
})
|> Publisher.perform()

Documentation

Docs for this library can be found at https://hexdocs.pm/herald.