messaging_service.ex

# web/services/messaging_service.ex
defmodule Publit.MessagingService do
  @moduledoc """
  Service to send notifications to the user
  """
  @message_api Application.get_env(:publit, :message_api)

  def status_code(resp) do
    {_s, msg} = resp
    {:error, msg}
  end

  def send_messages(tokens, data, cb_ok, cb_error, cb_net_error \\ fn(v) -> end) do
    Task.Supervisor.start_child(Publit.Messaging.Supervisor, fn() ->
        resp = @message_api.send_messages(tokens, data)
        case resp.status do
          :ok -> cb_ok.(resp)
          :error -> cb_error.(resp)
          :network_error -> cb_net_error.(resp)
        end
    end)
  end

  def send_direct_messages(tokens, data) do
    @message_api.send_messages(tokens, data)
  end
end

publit.ex

# lib/publit.ex
defmodule Publit do
  use Application

  # See http://elixir-lang.org/docs/stable/elixir/Application.html
  # for more information on OTP Applications
  def start(_type, _args) do
    import Supervisor.Spec

    # Define workers and child supervisors to be supervised
    children = [
      # Start the Ecto repository
      supervisor(Publit.Repo, []),
      # Start the endpoint when the application starts
      supervisor(Publit.Endpoint, []),
      supervisor(Task.Supervisor, [[name: Publit.Messaging.Supervisor]]),
      # Start your own worker by calling: Publit.Worker.start_link(arg1, arg2, arg3)
      # worker(Publit.Worker, [arg1, arg2, arg3])
      worker(Publit.CartService, [])
    ]

    # See http://elixir-lang.org/docs/stable/elixir/Supervisor.html
    # for other strategies and supported options
    opts = [strategy: :one_for_one, name: Publit.Supervisor]
    Supervisor.start_link(children, opts)
  end

  # Tell Phoenix to update the endpoint configuration
  # whenever the application is updated.
  def config_change(changed, _new, removed) do
    Publit.Endpoint.config_change(changed, removed)
    :ok
  end
end