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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.Gun.ConnectionPool.Reclaimer do
   6   use GenServer, restart: :temporary
   7
   8   @registry Pleroma.Gun.ConnectionPool
   9
  10   def start_monitor do
  11     pid =
  12       case :gen_server.start(__MODULE__, [], name: {:via, Registry, {@registry, "reclaimer"}}) do
  13         {:ok, pid} ->
  14           pid
  15
  16         {:error, {:already_registered, pid}} ->
  17           pid
  18       end
  19
  20     {pid, Process.monitor(pid)}
  21   end
  22
  23   @impl true
  24   def init(_) do
  25     {:ok, nil, {:continue, :reclaim}}
  26   end
  27
  28   @impl true
  29   def handle_continue(:reclaim, _) do
  30     max_connections = Pleroma.Config.get([:connections_pool, :max_connections])
  31
  32     reclaim_max =
  33       [:connections_pool, :reclaim_multiplier]
  34       |> Pleroma.Config.get()
  35       |> Kernel.*(max_connections)
  36       |> round
  37       |> max(1)
  38
  39     :telemetry.execute([:pleroma, :connection_pool, :reclaim, :start], %{}, %{
  40       max_connections: max_connections,
  41       reclaim_max: reclaim_max
  42     })
  43
  44     # :ets.fun2ms(
  45     # fn {_, {worker_pid, {_, used_by, crf, last_reference}}} when used_by == [] ->
  46     #   {worker_pid, crf, last_reference} end)
  47     unused_conns =
  48       Registry.select(
  49         @registry,
  50         [
  51           {{:_, :"$1", {:_, :"$2", :"$3", :"$4"}}, [{:==, :"$2", []}], [{{:"$1", :"$3", :"$4"}}]}
  52         ]
  53       )
  54
  55     case unused_conns do
  56       [] ->
  57         :telemetry.execute(
  58           [:pleroma, :connection_pool, :reclaim, :stop],
  59           %{reclaimed_count: 0},
  60           %{
  61             max_connections: max_connections
  62           }
  63         )
  64
  65         {:stop, :no_unused_conns, nil}
  66
  67       unused_conns ->
  68         reclaimed =
  69           unused_conns
  70           |> Enum.sort(fn {_pid1, crf1, last_reference1}, {_pid2, crf2, last_reference2} ->
  71             crf1 <= crf2 and last_reference1 <= last_reference2
  72           end)
  73           |> Enum.take(reclaim_max)
  74
  75         reclaimed
  76         |> Enum.each(fn {pid, _, _} ->
  77           DynamicSupervisor.terminate_child(Pleroma.Gun.ConnectionPool.WorkerSupervisor, pid)
  78         end)
  79
  80         :telemetry.execute(
  81           [:pleroma, :connection_pool, :reclaim, :stop],
  82           %{reclaimed_count: Enum.count(reclaimed)},
  83           %{max_connections: max_connections}
  84         )
  85
  86         {:stop, :normal, nil}
  87     end
  88   end
  89 end