A GenServer Poller

poller.ex

defmodule Poller do
  use GenServer

  def start_link do
    # this starts the genserver (for supervision)
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
  end

  def init(_) do
    set_timer
    {:ok, []}
  end

  def execute do
    GenServer.cast(__MODULE__, :do_the_task)
  end

  def set_timer do
    delay_in_ms = 3_000
    :timer.apply_after(delay_in_ms, __MODULE__, :execute, [])
  end

  def handle_cast(:do_the_task, state) do
    set_timer
    # this where you'd do the task
    do_the_task
    {:noreply, state}
  end

  def do_the_task do
    IO.puts("Task was done @ #{DateTime.utc_now |> to_string}")
  end
end