defmodule Pleroma.Gun.ConnectionPool.Worker do alias Pleroma.Gun use GenServer, restart: :temporary @registry Pleroma.Gun.ConnectionPool def start_link(opts) do GenServer.start_link(__MODULE__, opts) end @impl true def init([uri, key, opts, client_pid]) do time = :os.system_time(:second) # Register before opening connection to prevent race conditions with {:ok, _owner} <- Registry.register(@registry, key, {nil, [client_pid], 1, time}), {:ok, conn_pid} <- Gun.Conn.open(uri, opts), Process.link(conn_pid) do {_, _} = Registry.update_value(@registry, key, fn {_, used_by, crf, last_reference} -> {conn_pid, used_by, crf, last_reference} end) send(client_pid, {:conn_pid, conn_pid}) {:ok, %{key: key, timer: nil}, :hibernate} else err -> {:stop, err} end end @impl true def handle_cast({:add_client, client_pid, send_pid_back}, %{key: key} = state) do time = :os.system_time(:second) {{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 {: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) 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 # 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, time_delta / 100) * prev_crf end end