closing idle gun connections

config/config.exs

@@ -608,6 +608,8 @@ config :pleroma, Pleroma.Repo,
 config :pleroma, :connections_pool,
   checkin_timeout: 250,
   max_connections: 250,
+  max_idle_time: 10,
+  closing_idle_conns_interval: 10,
   retry: 1,
   retry_timeout: 1000,
   await_up_timeout: 5_000

docs/configuration/cheatsheet.md

@@ -394,15 +394,20 @@ For each pool, the options are:
 
 Advanced settings for connections pool. Pool with opened connections. These connections can be reused in worker pools.
 
-For big instances it's recommended to increase `config :pleroma, :connections_pool, max_connections: 500` up to 500-1000.
-It will increase memory usage, but federation would work faster.
+For big instances it's recommended to increase `max_connections` up to 500-1000. It will increase memory usage, but federation would work faster.
 
 * `:checkin_timeout` - timeout to checkin connection from pool. Default: 250ms.
 * `:max_connections` - maximum number of connections in the pool. Default: 250 connections.
+* `:max_idle_time` - maximum of time, while connection can be idle. Default: 10 minutes.
+* `:closing_idle_conns_interval` - interval between cleaning pool from idle connections. Default: 10 minutes.
 * `:retry` - number of retries, while `gun` will try to reconnect if connection goes down. Default: 1.
 * `:retry_timeout` - time between retries when `gun` will try to reconnect in milliseconds. Default: 1000ms.
 * `:await_up_timeout` - timeout while `gun` will wait until connection is up. Default: 5000ms.
 
+*If you are increasing `max_connections` setting, dont't forget to increase limit for file descriptors:*
+* `installation/pleroma.service` - `LimitNOFILE`
+* `installation/pleroma.supervisord` - `minfds`
+
 ### :pools
 
 *For `gun` adapter*

lib/pleroma/pool/connections.ex

@@ -12,6 +12,7 @@ defmodule Pleroma.Pool.Connections do
 
   @type domain :: String.t()
   @type conn :: Pleroma.Gun.Conn.t()
+  @type seconds :: pos_integer()
 
   @type t :: %__MODULE__{
           conns: %{domain() => conn()},
@@ -26,7 +27,10 @@ defmodule Pleroma.Pool.Connections do
   end
 
   @impl true
-  def init(opts), do: {:ok, %__MODULE__{conns: %{}, opts: opts}}
+  def init(opts) do
+    schedule_close_idle_conns()
+    {:ok, %__MODULE__{conns: %{}, opts: opts}}
+  end
 
   @spec checkin(String.t() | URI.t(), atom()) :: pid() | nil
   def checkin(url, name)
@@ -154,16 +158,16 @@ defmodule Pleroma.Pool.Connections do
   def handle_call(:unused_conns, _from, state) do
     unused_conns =
       state.conns
-      |> Enum.filter(&filter_conns/1)
-      |> Enum.sort(&sort_conns/2)
+      |> Enum.filter(&idle_conn?/1)
+      |> Enum.sort(&least_used/2)
 
     {:reply, unused_conns, state}
   end
 
-  defp filter_conns({_, %{conn_state: :idle, used_by: []}}), do: true
-  defp filter_conns(_), do: false
+  defp idle_conn?({_, %{conn_state: :idle}}), do: true
+  defp idle_conn?(_), do: false
 
-  defp sort_conns({_, c1}, {_, c2}) do
+  defp least_used({_, c1}, {_, c2}) do
     c1.crf <= c2.crf and c1.last_reference <= c2.last_reference
   end
 
@@ -265,6 +269,38 @@ defmodule Pleroma.Pool.Connections do
     {:noreply, state}
   end
 
+  @impl true
+  def handle_info({:close_idle_conns, max_idle_time}, state) do
+    closing_time = :os.system_time(:second) - max_idle_time
+
+    idle_conns_keys =
+      state.conns
+      |> Enum.filter(&idle_more_than?(&1, closing_time))
+      |> Enum.map(fn {key, %{conn: conn}} ->
+        Gun.close(conn)
+        key
+      end)
+
+    schedule_close_idle_conns()
+    {:noreply, put_in(state.conns, Map.drop(state.conns, idle_conns_keys))}
+  end
+
+  defp schedule_close_idle_conns do
+    max_idle_time = Config.get([:connections_pool, :max_idle_time], 10) * 60
+    interval = Config.get([:connections_pool, :closing_idle_conns_interval], 10) * 60 * 1000
+    Process.send_after(self(), {:close_idle_conns, max_idle_time}, interval)
+  end
+
+  defp idle_more_than?(
+         {_, %{conn_state: :idle, last_reference: idle_since}},
+         closing_time
+       )
+       when closing_time >= idle_since do
+    true
+  end
+
+  defp idle_more_than?(_, _), do: false
+
   defp find_conn(conns, conn_pid) do
     Enum.find(conns, fn {_key, conn} ->
       conn.conn == conn_pid

test/pool/connections_test.exs

@@ -757,4 +757,38 @@ defmodule Pleroma.Pool.ConnectionsTest do
     Connections.remove_conn(name, "1")
     assert Connections.count(name) == 0
   end
+
+  test "close_idle_conns/2", %{name: name} do
+    GunMock
+    |> expect(:close, fn _ -> :ok end)
+    |> allow(self(), name)
+
+    Connections.add_conn(name, "1", %Conn{
+      conn_state: :idle,
+      last_reference: now() - 30,
+      conn: self()
+    })
+
+    Connections.add_conn(name, "2", %Conn{
+      conn_state: :idle,
+      last_reference: now() - 10,
+      conn: self()
+    })
+
+    Connections.add_conn(name, "3", %Conn{
+      conn_state: :active,
+      conn: self()
+    })
+
+    name
+    |> Process.whereis()
+    |> send({:close_idle_conns, 15})
+
+    assert %Connections{
+             conns: %{
+               "3" => %Conn{},
+               "2" => %Conn{}
+             }
+           } = Connections.get_state(name)
+  end
 end