defmodule Pleroma.Gun.ConnectionPool.Worker do alias Pleroma.Gun use GenServer, restart: :temporary @registry Pleroma.Gun.ConnectionPool def start_link([key | _] = opts) do GenServer.start_link(__MODULE__, opts, name: {:via, Registry, {@registry, key}}) end @impl true def init([_key, _uri, _opts, _client_pid] = opts) do {:ok, nil, {:continue, {:connect, opts}}} end @impl true def handle_continue({:connect, [key, uri, opts, client_pid]}, _) do with {:ok, conn_pid} <- Gun.Conn.open(uri, opts), Process.link(conn_pid) do time = :erlang.monotonic_time(:millisecond) {_, _} = Registry.update_value(@registry, key, fn _ -> {conn_pid, [client_pid], 1, time} end) send(client_pid, {:conn_pid, conn_pid}) {:noreply, %{key: key, timer: nil, client_monitors: %{client_pid => Process.monitor(client_pid)}}, :hibernate} else err -> {:stop, err, nil} end end @impl true def handle_cast({:add_client, client_pid, send_pid_back}, %{key: key} = state) do time = :erlang.monotonic_time(:millisecond) {{conn_pid, _, _, _}, _} = Registry.update_value(@registry, key, fn {conn_pid, used_by, crf, last_reference} -> {conn_pid, [client_pid | used_by], crf(time - last_reference, crf), time} end) if send_pid_back, do: send(client_pid, {:conn_pid, conn_pid}) state = if state.timer != nil do Process.cancel_timer(state[:timer]) %{state | timer: nil} else state end ref = Process.monitor(client_pid) state = put_in(state.client_monitors[client_pid], ref) {:noreply, state, :hibernate} end @impl true def handle_cast({:remove_client, client_pid}, %{key: key} = state) do {{_conn_pid, used_by, _crf, _last_reference}, _} = Registry.update_value(@registry, key, fn {conn_pid, used_by, crf, last_reference} -> {conn_pid, List.delete(used_by, client_pid), crf, last_reference} end) {ref, state} = pop_in(state.client_monitors[client_pid]) Process.demonitor(ref) timer = if used_by == [] do max_idle = Pleroma.Config.get([:connections_pool, :max_idle_time], 30_000) Process.send_after(self(), :idle_close, max_idle) else nil end {:noreply, %{state | timer: timer}, :hibernate} end @impl true def handle_info(:idle_close, state) do # Gun monitors the owner process, and will close the connection automatically # when it's terminated {:stop, :normal, state} end # Gracefully shutdown if the connection got closed without any streams left @impl true def handle_info({:gun_down, _pid, _protocol, _reason, []}, state) do {:stop, :normal, state} end # Otherwise, shutdown with an error @impl true def handle_info({:gun_down, _pid, _protocol, _reason, _killed_streams} = down_message, state) do {:stop, {:error, down_message}, state} end @impl true def handle_info({:DOWN, _ref, :process, pid, reason}, state) do # Sometimes the client is dead before we demonitor it in :remove_client, so the message # arrives anyway case state.client_monitors[pid] do nil -> {:noreply, state, :hibernate} _ref -> :telemetry.execute( [:pleroma, :connection_pool, :client_death], %{client_pid: pid, reason: reason}, %{key: state.key} ) handle_cast({:remove_client, pid}, state) end end # LRFU policy: https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.55.1478 defp crf(time_delta, prev_crf) do 1 + :math.pow(0.5, 0.0001 * time_delta) * prev_crf end end