gen_event.exs

{:ok, manager} = GenEvent.start_link
stream = GenEvent.stream(manager, [mode: :async])

pid1 = spawn_link fn ->
  for x <- stream do
    IO.puts "pid1 -> sleeping for 1 second then inspecting"
    :timer.sleep(1000)
    IO.inspect(x)
  end
end

pid2 = spawn_link fn ->
  for x <- stream do
    IO.puts "pid2 -> sleeping for 2 seconds then inspecting"
    :timer.sleep(2000)
    IO.inspect(x)
  end
end

iex> for x <- [1,2,3,4,5], do: GenEvent.notify(manager, x)
[:ok, :ok, :ok, :ok, :ok]
pid2 -> sleeping for 2 seconds then inspecting
1
pid1 -> sleeping for 1 second then inspecting
1
pid2 -> sleeping for 2 seconds then inspecting
2
pid1 -> sleeping for 1 second then inspecting
2
pid2 -> sleeping for 2 seconds then inspecting
3
pid1 -> sleeping for 1 second then inspecting
3
pid2 -> sleeping for 2 seconds then inspecting
4
pid1 -> sleeping for 1 second then inspecting
4
pid2 -> sleeping for 2 seconds then inspecting
5
pid1 -> sleeping for 1 second then inspecting
5