Great to hear you got this working!

As you’ve figured out, once you get a handle on the root Bandit process (which is actually just a Thousand Island server process), you can get the list of current connection processes for it via the ThousandIsland.connection_pids/1 function added in Thousand Island 0.5.17. That part is pretty straightforward.

This leaves the problem of how to get the Bandit/Thousand Island pid from an Endpoint process (accessible via id as the Endpoint’s module name). Pulling out specific children of a supervisor (by id or otherwise) is always as awkward as you’ve done here; there’s not really an easier way. There’s a million ways to golf this sort of thing down to something more elegant but I’ve never really seen an approach I like; curious if anyone else has a better approach. FWIW I use a pattern more or less like you do here within Thousand Island.

Cool, thanks!

For future reference, here’s the snippet using everything I learned today

 defp shutdown_when_inactive(every_ms) do
    Process.sleep(every_ms)

    {_, pid, _, _} =
      AppWeb.Endpoint
      |> Supervisor.which_children()
      |> Enum.find(&Kernel.match?({{AppWeb.Endpoint, :http}, _pid, _type, [Bandit]}, &1))

    {:ok, connections} = ThousandIsland.connection_pids(pid)

    if connections == [] do
      System.stop(0)
    else
      shutdown_when_inactive(every_ms)
    end
  end

Yeah, your approach is more elegant than mine, similar idea, cleaner execution, still wondering if someone has a different approach.

Thanks again

:worker or :supervisor at the place you indicate is a record of the type field from the child spec (see Supervisor — Elixir v1.14.3). The value of this field isn’t super material to you one way or the other; your match can safely ignore it.

(As background, Bandit’s behaviour in this regard had some minor chages with the 0.6.11 release that moved that field from :worker to :supervisor. It’s a purely internal change that you don’t really need to care about).