elli_handler.ex

defmodule Web do
  require Logger

  @behaviour :elli_handler

  def handle(r, _args) do
    Router.handle(:elli_request.method(r), :elli_request.path(r), r)
  rescue
    exception ->
      Logger.error(inspect(exception))
      {500, [], "Internal server error"}
  end

  def handle_event(:request_complete, data, _args), do: log_request(data)
  def handle_event(_event, _data, _args), do: :ok

  defp log_request(data) do
    [req, code, _headers, _body, {timings, _sizes}] = data

    start = :erlang.convert_time_unit(timings[:request_start], :native, :microsecond)
    finish = :erlang.convert_time_unit(timings[:request_end], :native, :microsecond)
    request_microseconds = finish - start

    msg = [
      to_string(:elli_request.method(req)),
      ?\s,
      :elli_request.raw_path(req),
      ?\s,
      to_string(code),
      ?\s,
      to_string(request_microseconds),
      "μs"
    ]

    Logger.info(msg, request_microseconds: request_microseconds)
  end
end

router.ex

defmodule Router do
  def handle(:GET, ["ping"], req) do
    {200, [], "pong"}
  end

  def handle(_method, _path, _req) do
    {404, [], "Not found"}
  end
end

@crowdhailed Anything you want, you pass it in the child spec