elixir periodically

periodic_worker.ex

defmodule PeriodicWorker do
  use GenServer

  @impl true
  def init(period_in_millis) do
    # The `{:continue, :init}` tuple here instructs OTP to run `handle_continue`
    # which in this case will fire the first `:do_stuff` message so the worker
    # does its job once and then schedules itself to run again in the future.
    # Without this you'd have to manually fire the message to the worker
    # when your app starts.
    {:ok, period_in_millis, {:continue, :init}}
  end

  def handle_continue(:init, period_in_millis) do
    GenServer.call(self(), {:do_stuff, period_in_millis})
  end

  @impl true
  def handle_call(:do_stuff, _caller_pid, period_in_millis) do
    do_the_thing_you_need_done_periodically_here()

    schedule_next_do_stuff(period_in_millis)

    # or change `:ok` to the return value of the function that does the real work.
    {:reply, :ok}
  end

  def schedule_next_do_stuff(period_in_millis) do
    Process.send_after(self(), :do_stuff, period_in_millis)
  end
end

your_app.ex

defmodule YourApp do
  use Application

  def start(_type, _args) d
    children = [
      {PeriodicWorker, 4 * 60 * 60 * 1000}, # 4 hours
      # ... other children ....
    ]

    options = [strategy: :one_for_one, name: YourApp.Supervisor]
    Supervisor.start_link(children, options)
  end
end