Refactor gun pooling and simplify adapter option insertion

This patch refactors gun pooling to use Elixir process registry and
simplifies adapter option insertion.

Having the pool use process registry instead of a GenServer has a number of advantages:
- Simpler code: the initial implementation adds about half the lines of code it deletes
- Concurrency: unlike a GenServer, ETS-based registry can handle multiple checkout/checkin
requests at the same time
- Precise and easy idle connection clousure: current proposal for closing idle connections in
the GenServer-based pool needs to filter through all connections once a minute and compare their
last active time with closing time. With Elixir process registry this can be done
by just using `Process.send_after`/`Process.cancel_timer` in the worker process.
- Lower memory footprint: In my tests `gun-memory-leak` branch uses about 290mb on peak load (250 connections)
and 235mb on idle (5-10 connections). Registry-based pool uses 210mb on idle and 240mb on peak load

config/config.exs

@@ -647,8 +647,10 @@
   prepare: :unnamed
 
 config :pleroma, :connections_pool,
+  reclaim_multiplier: 0.1,
   checkin_timeout: 250,
   max_connections: 250,
+  max_idle_time: 30_000,
   retry: 1,
   retry_timeout: 1000,
   await_up_timeout: 5_000

lib/pleroma/application.ex

@@ -223,9 +223,7 @@ defp task_children(_) do
 
   # start hackney and gun pools in tests
   defp http_children(_, :test) do
-    hackney_options = Config.get([:hackney_pools, :federation])
+    http_children(Tesla.Adapter.Hackney, nil) ++ http_children(Tesla.Adapter.Gun, nil)
-    hackney_pool = :hackney_pool.child_spec(:federation, hackney_options)
-    [hackney_pool, Pleroma.Pool.Supervisor]
   end
 
   defp http_children(Tesla.Adapter.Hackney, _) do
@@ -244,7 +242,9 @@ defp http_children(Tesla.Adapter.Hackney, _) do
     end
   end
 
-  defp http_children(Tesla.Adapter.Gun, _), do: [Pleroma.Pool.Supervisor]
+  defp http_children(Tesla.Adapter.Gun, _) do
+    [{Registry, keys: :unique, name: Pleroma.Gun.ConnectionPool}]
+  end
 
   defp http_children(_, _), do: []
 end

lib/pleroma/gun/conn.ex

@@ -3,40 +3,11 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Gun.Conn do
-  @moduledoc """
-  Struct for gun connection data
-  """
   alias Pleroma.Gun
-  alias Pleroma.Pool.Connections
 
   require Logger
 
-  @type gun_state :: :up | :down
+  def open(%URI{} = uri, opts) do
-  @type conn_state :: :active | :idle
-
-  @type t :: %__MODULE__{
-          conn: pid(),
-          gun_state: gun_state(),
-          conn_state: conn_state(),
-          used_by: [pid()],
-          last_reference: pos_integer(),
-          crf: float(),
-          retries: pos_integer()
-        }
-
-  defstruct conn: nil,
-            gun_state: :open,
-            conn_state: :init,
-            used_by: [],
-            last_reference: 0,
-            crf: 1,
-            retries: 0
-
-  @spec open(String.t() | URI.t(), atom(), keyword()) :: :ok | nil
-  def open(url, name, opts \\ [])
-  def open(url, name, opts) when is_binary(url), do: open(URI.parse(url), name, opts)
-
-  def open(%URI{} = uri, name, opts) do
     pool_opts = Pleroma.Config.get([:connections_pool], [])
 
     opts =
@@ -45,30 +16,10 @@ def open(%URI{} = uri, name, opts) do
       |> Map.put_new(:retry, pool_opts[:retry] || 1)
       |> Map.put_new(:retry_timeout, pool_opts[:retry_timeout] || 1000)
       |> Map.put_new(:await_up_timeout, pool_opts[:await_up_timeout] || 5_000)
+      |> Map.put_new(:supervise, false)
       |> maybe_add_tls_opts(uri)
 
-    key = "#{uri.scheme}:#{uri.host}:#{uri.port}"
+    do_open(uri, opts)
-
-    max_connections = pool_opts[:max_connections] || 250
-
-    conn_pid =
-      if Connections.count(name) < max_connections do
-        do_open(uri, opts)
-      else
-        close_least_used_and_do_open(name, uri, opts)
-      end
-
-    if is_pid(conn_pid) do
-      conn = %Pleroma.Gun.Conn{
-        conn: conn_pid,
-        gun_state: :up,
-        conn_state: :active,
-        last_reference: :os.system_time(:second)
-      }
-
-      :ok = Gun.set_owner(conn_pid, Process.whereis(name))
-      Connections.add_conn(name, key, conn)
-    end
   end
 
   defp maybe_add_tls_opts(opts, %URI{scheme: "http"}), do: opts
@@ -81,7 +32,7 @@ defp maybe_add_tls_opts(opts, %URI{scheme: "https", host: host}) do
       reuse_sessions: false,
       verify_fun:
         {&:ssl_verify_hostname.verify_fun/3,
-         [check_hostname: Pleroma.HTTP.Connection.format_host(host)]}
+         [check_hostname: Pleroma.HTTP.AdapterHelper.format_host(host)]}
     ]
 
     tls_opts =
@@ -105,7 +56,7 @@ defp do_open(uri, %{proxy: {proxy_host, proxy_port}} = opts) do
          {:ok, _} <- Gun.await_up(conn, opts[:await_up_timeout]),
          stream <- Gun.connect(conn, connect_opts),
          {:response, :fin, 200, _} <- Gun.await(conn, stream) do
-      conn
+      {:ok, conn}
     else
       error ->
         Logger.warn(
@@ -141,7 +92,7 @@ defp do_open(uri, %{proxy: {proxy_type, proxy_host, proxy_port}} = opts) do
 
     with {:ok, conn} <- Gun.open(proxy_host, proxy_port, opts),
          {:ok, _} <- Gun.await_up(conn, opts[:await_up_timeout]) do
-      conn
+      {:ok, conn}
     else
       error ->
         Logger.warn(
@@ -155,11 +106,11 @@ defp do_open(uri, %{proxy: {proxy_type, proxy_host, proxy_port}} = opts) do
   end
 
   defp do_open(%URI{host: host, port: port} = uri, opts) do
-    host = Pleroma.HTTP.Connection.parse_host(host)
+    host = Pleroma.HTTP.AdapterHelper.parse_host(host)
 
     with {:ok, conn} <- Gun.open(host, port, opts),
          {:ok, _} <- Gun.await_up(conn, opts[:await_up_timeout]) do
-      conn
+      {:ok, conn}
     else
       error ->
         Logger.warn(
@@ -171,7 +122,7 @@ defp do_open(%URI{host: host, port: port} = uri, opts) do
   end
 
   defp destination_opts(%URI{host: host, port: port}) do
-    host = Pleroma.HTTP.Connection.parse_host(host)
+    host = Pleroma.HTTP.AdapterHelper.parse_host(host)
     %{host: host, port: port}
   end
 
@@ -181,17 +132,6 @@ defp add_http2_opts(opts, "https", tls_opts) do
 
   defp add_http2_opts(opts, _, _), do: opts
 
-  defp close_least_used_and_do_open(name, uri, opts) do
-    with [{key, conn} | _conns] <- Connections.get_unused_conns(name),
-         :ok <- Gun.close(conn.conn) do
-      Connections.remove_conn(name, key)
-
-      do_open(uri, opts)
-    else
-      [] -> {:error, :pool_overflowed}
-    end
-  end
-
   def compose_uri_log(%URI{scheme: scheme, host: host, path: path}) do
     "#{scheme}://#{host}#{path}"
   end

lib/pleroma/gun/connection_pool.ex

@@ -0,0 +1,129 @@
+defmodule Pleroma.Gun.ConnectionPool do
+  @registry __MODULE__
+
+  def get_conn(uri, opts) do
+    case enforce_pool_limits() do
+      :ok ->
+        key = "#{uri.scheme}:#{uri.host}:#{uri.port}"
+
+        case Registry.lookup(@registry, key) do
+          # The key has already been registered, but connection is not up yet
+          [{worker_pid, {nil, _used_by, _crf, _last_reference}}] ->
+            get_gun_pid_from_worker(worker_pid)
+
+          [{worker_pid, {gun_pid, _used_by, _crf, _last_reference}}] ->
+            GenServer.cast(worker_pid, {:add_client, self(), false})
+            {:ok, gun_pid}
+
+          [] ->
+            # :gun.set_owner fails in :connected state for whatevever reason,
+            # so we open the connection in the process directly and send it's pid back
+            # We trust gun to handle timeouts by itself
+            case GenServer.start(Pleroma.Gun.ConnectionPool.Worker, [uri, key, opts, self()],
+                   timeout: :infinity
+                 ) do
+              {:ok, _worker_pid} ->
+                receive do
+                  {:conn_pid, pid} -> {:ok, pid}
+                end
+
+              {:error, {:error, {:already_registered, worker_pid}}} ->
+                get_gun_pid_from_worker(worker_pid)
+
+              err ->
+                err
+            end
+        end
+
+      :error ->
+        {:error, :pool_full}
+    end
+  end
+
+  @enforcer_key "enforcer"
+  defp enforce_pool_limits() do
+    max_connections = Pleroma.Config.get([:connections_pool, :max_connections])
+
+    if Registry.count(@registry) >= max_connections do
+      case Registry.lookup(@registry, @enforcer_key) do
+        [] ->
+          pid =
+            spawn(fn ->
+              {:ok, _pid} = Registry.register(@registry, @enforcer_key, nil)
+
+              reclaim_max =
+                [:connections_pool, :reclaim_multiplier]
+                |> Pleroma.Config.get()
+                |> Kernel.*(max_connections)
+                |> round
+                |> max(1)
+
+              unused_conns =
+                Registry.select(
+                  @registry,
+                  [
+                    {{:_, :"$1", {:_, :"$2", :"$3", :"$4"}}, [{:==, :"$2", []}],
+                     [{{:"$1", :"$3", :"$4"}}]}
+                  ]
+                )
+
+              case unused_conns do
+                [] ->
+                  exit(:pool_full)
+
+                unused_conns ->
+                  unused_conns
+                  |> Enum.sort(fn {_pid1, crf1, last_reference1},
+                                  {_pid2, crf2, last_reference2} ->
+                    crf1 <= crf2 and last_reference1 <= last_reference2
+                  end)
+                  |> Enum.take(reclaim_max)
+                  |> Enum.each(fn {pid, _, _} -> GenServer.call(pid, :idle_close) end)
+              end
+            end)
+
+          wait_for_enforcer_finish(pid)
+
+        [{pid, _}] ->
+          wait_for_enforcer_finish(pid)
+      end
+    else
+      :ok
+    end
+  end
+
+  defp wait_for_enforcer_finish(pid) do
+    ref = Process.monitor(pid)
+
+    receive do
+      {:DOWN, ^ref, :process, ^pid, :pool_full} ->
+        :error
+
+      {:DOWN, ^ref, :process, ^pid, :normal} ->
+        :ok
+    end
+  end
+
+  defp get_gun_pid_from_worker(worker_pid) do
+    # GenServer.call will block the process for timeout length if
+    # the server crashes on startup (which will happen if gun fails to connect)
+    # so instead we use cast + monitor
+
+    ref = Process.monitor(worker_pid)
+    GenServer.cast(worker_pid, {:add_client, self(), true})
+
+    receive do
+      {:conn_pid, pid} -> {:ok, pid}
+      {:DOWN, ^ref, :process, ^worker_pid, reason} -> reason
+    end
+  end
+
+  def release_conn(conn_pid) do
+    [worker_pid] =
+      Registry.select(@registry, [
+        {{:_, :"$1", {:"$2", :_, :_, :_}}, [{:==, :"$2", conn_pid}], [:"$1"]}
+      ])
+
+    GenServer.cast(worker_pid, {:remove_client, self()})
+  end
+end

lib/pleroma/gun/connection_pool/worker.ex

@@ -0,0 +1,95 @@
+defmodule Pleroma.Gun.ConnectionPool.Worker do
+  alias Pleroma.Gun
+  use GenServer
+
+  @registry Pleroma.Gun.ConnectionPool
+
+  @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
+
+  @impl true
+  def handle_call(:idle_close, _, %{key: key} = state) do
+    Registry.unregister(@registry, key)
+    {:stop, :normal, 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

lib/pleroma/http/adapter_helper.ex

@@ -3,7 +3,21 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.HTTP.AdapterHelper do
-  alias Pleroma.HTTP.Connection
+  @moduledoc """
+  Configure Tesla.Client with default and customized adapter options.
+  """
+  @defaults [pool: :federation]
+
+  @type ip_address :: ipv4_address() | ipv6_address()
+  @type ipv4_address :: {0..255, 0..255, 0..255, 0..255}
+  @type ipv6_address ::
+          {0..65_535, 0..65_535, 0..65_535, 0..65_535, 0..65_535, 0..65_535, 0..65_535, 0..65_535}
+  @type proxy_type() :: :socks4 | :socks5
+  @type host() :: charlist() | ip_address()
+
+  alias Pleroma.Config
+  alias Pleroma.HTTP.AdapterHelper
+  require Logger
 
   @type proxy ::
           {Connection.host(), pos_integer()}
@@ -11,24 +25,13 @@ defmodule Pleroma.HTTP.AdapterHelper do
 
   @callback options(keyword(), URI.t()) :: keyword()
   @callback after_request(keyword()) :: :ok
-
+  @callback get_conn(URI.t(), keyword()) :: {:ok, term()} | {:error, term()}
-  @spec options(keyword(), URI.t()) :: keyword()
-  def options(opts, _uri) do
-    proxy = Pleroma.Config.get([:http, :proxy_url], nil)
-    maybe_add_proxy(opts, format_proxy(proxy))
-  end
-
-  @spec maybe_get_conn(URI.t(), keyword()) :: keyword()
-  def maybe_get_conn(_uri, opts), do: opts
-
-  @spec after_request(keyword()) :: :ok
-  def after_request(_opts), do: :ok
 
   @spec format_proxy(String.t() | tuple() | nil) :: proxy() | nil
   def format_proxy(nil), do: nil
 
   def format_proxy(proxy_url) do
-    case Connection.parse_proxy(proxy_url) do
+    case parse_proxy(proxy_url) do
       {:ok, host, port} -> {host, port}
       {:ok, type, host, port} -> {type, host, port}
       _ -> nil
@@ -38,4 +41,106 @@ def format_proxy(proxy_url) do
   @spec maybe_add_proxy(keyword(), proxy() | nil) :: keyword()
   def maybe_add_proxy(opts, nil), do: opts
   def maybe_add_proxy(opts, proxy), do: Keyword.put_new(opts, :proxy, proxy)
+
+  @doc """
+  Merge default connection & adapter options with received ones.
+  """
+
+  @spec options(URI.t(), keyword()) :: keyword()
+  def options(%URI{} = uri, opts \\ []) do
+    @defaults
+    |> pool_timeout()
+    |> Keyword.merge(opts)
+    |> adapter_helper().options(uri)
+  end
+
+  defp pool_timeout(opts) do
+    {config_key, default} =
+      if adapter() == Tesla.Adapter.Gun do
+        {:pools, Config.get([:pools, :default, :timeout])}
+      else
+        {:hackney_pools, 10_000}
+      end
+
+    timeout = Config.get([config_key, opts[:pool], :timeout], default)
+
+    Keyword.merge(opts, timeout: timeout)
+  end
+
+  @spec after_request(keyword()) :: :ok
+  def after_request(opts), do: adapter_helper().after_request(opts)
+
+  def get_conn(uri, opts), do: adapter_helper().get_conn(uri, opts)
+  defp adapter, do: Application.get_env(:tesla, :adapter)
+
+  defp adapter_helper do
+    case adapter() do
+      Tesla.Adapter.Gun -> AdapterHelper.Gun
+      Tesla.Adapter.Hackney -> AdapterHelper.Hackney
+      _ -> AdapterHelper.Default
+    end
+  end
+
+  @spec parse_proxy(String.t() | tuple() | nil) ::
+          {:ok, host(), pos_integer()}
+          | {:ok, proxy_type(), host(), pos_integer()}
+          | {:error, atom()}
+          | nil
+
+  def parse_proxy(nil), do: nil
+
+  def parse_proxy(proxy) when is_binary(proxy) do
+    with [host, port] <- String.split(proxy, ":"),
+         {port, ""} <- Integer.parse(port) do
+      {:ok, parse_host(host), port}
+    else
+      {_, _} ->
+        Logger.warn("Parsing port failed #{inspect(proxy)}")
+        {:error, :invalid_proxy_port}
+
+      :error ->
+        Logger.warn("Parsing port failed #{inspect(proxy)}")
+        {:error, :invalid_proxy_port}
+
+      _ ->
+        Logger.warn("Parsing proxy failed #{inspect(proxy)}")
+        {:error, :invalid_proxy}
+    end
+  end
+
+  def parse_proxy(proxy) when is_tuple(proxy) do
+    with {type, host, port} <- proxy do
+      {:ok, type, parse_host(host), port}
+    else
+      _ ->
+        Logger.warn("Parsing proxy failed #{inspect(proxy)}")
+        {:error, :invalid_proxy}
+    end
+  end
+
+  @spec parse_host(String.t() | atom() | charlist()) :: charlist() | ip_address()
+  def parse_host(host) when is_list(host), do: host
+  def parse_host(host) when is_atom(host), do: to_charlist(host)
+
+  def parse_host(host) when is_binary(host) do
+    host = to_charlist(host)
+
+    case :inet.parse_address(host) do
+      {:error, :einval} -> host
+      {:ok, ip} -> ip
+    end
+  end
+
+  @spec format_host(String.t()) :: charlist()
+  def format_host(host) do
+    host_charlist = to_charlist(host)
+
+    case :inet.parse_address(host_charlist) do
+      {:error, :einval} ->
+        :idna.encode(host_charlist)
+
+      {:ok, _ip} ->
+        host_charlist
+    end
+  end
 end

lib/pleroma/http/adapter_helper/default.ex

@@ -0,0 +1,17 @@
+defmodule Pleroma.HTTP.AdapterHelper.Default do
+  alias Pleroma.HTTP.AdapterHelper
+
+  @behaviour Pleroma.HTTP.AdapterHelper
+
+  @spec options(keyword(), URI.t()) :: keyword()
+  def options(opts, _uri) do
+    proxy = Pleroma.Config.get([:http, :proxy_url], nil)
+    AdapterHelper.maybe_add_proxy(opts, AdapterHelper.format_proxy(proxy))
+  end
+
+  @spec after_request(keyword()) :: :ok
+  def after_request(_opts), do: :ok
+
+  @spec get_conn(URI.t(), keyword()) :: {:ok, keyword()}
+  def get_conn(_uri, opts), do: {:ok, opts}
+end

lib/pleroma/http/adapter_helper/gun.ex

@@ -5,8 +5,8 @@
 defmodule Pleroma.HTTP.AdapterHelper.Gun do
   @behaviour Pleroma.HTTP.AdapterHelper
 
+  alias Pleroma.Gun.ConnectionPool
   alias Pleroma.HTTP.AdapterHelper
-  alias Pleroma.Pool.Connections
 
   require Logger
 
@@ -31,13 +31,13 @@ def options(incoming_opts \\ [], %URI{} = uri) do
     |> Keyword.merge(config_opts)
     |> add_scheme_opts(uri)
     |> AdapterHelper.maybe_add_proxy(proxy)
-    |> maybe_get_conn(uri, incoming_opts)
+    |> Keyword.merge(incoming_opts)
   end
 
   @spec after_request(keyword()) :: :ok
   def after_request(opts) do
     if opts[:conn] && opts[:body_as] != :chunks do
-      Connections.checkout(opts[:conn], self(), :gun_connections)
+      ConnectionPool.release_conn(opts[:conn])
     end
 
     :ok
@@ -51,27 +51,11 @@ defp add_scheme_opts(opts, %{scheme: "https"}) do
     |> Keyword.put(:tls_opts, log_level: :warning)
   end
 
-  defp maybe_get_conn(adapter_opts, uri, incoming_opts) do
+  @spec get_conn(URI.t(), keyword()) :: {:ok, keyword()} | {:error, atom()}
-    {receive_conn?, opts} =
+  def get_conn(uri, opts) do
-      adapter_opts
+    case ConnectionPool.get_conn(uri, opts) do
-      |> Keyword.merge(incoming_opts)
+      {:ok, conn_pid} -> {:ok, Keyword.merge(opts, conn: conn_pid, close_conn: false)}
-      |> Keyword.pop(:receive_conn, true)
+      err -> err
-
-    if Connections.alive?(:gun_connections) and receive_conn? do
-      checkin_conn(uri, opts)
-    else
-      opts
-    end
-  end
-
-  defp checkin_conn(uri, opts) do
-    case Connections.checkin(uri, :gun_connections) do
-      nil ->
-        Task.start(Pleroma.Gun.Conn, :open, [uri, :gun_connections, opts])
-        opts
-
-      conn when is_pid(conn) ->
-        Keyword.merge(opts, conn: conn, close_conn: false)
     end
   end
 end

lib/pleroma/http/adapter_helper/hackney.ex

@@ -25,4 +25,7 @@ def options(connection_opts \\ [], %URI{} = uri) do
   defp add_scheme_opts(opts, _), do: opts
 
   def after_request(_), do: :ok
+
+  @spec get_conn(URI.t(), keyword()) :: {:ok, keyword()}
+  def get_conn(_uri, opts), do: {:ok, opts}
 end

lib/pleroma/http/connection.ex

@@ -1,124 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.HTTP.Connection do
-  @moduledoc """
-  Configure Tesla.Client with default and customized adapter options.
-  """
-
-  alias Pleroma.Config
-  alias Pleroma.HTTP.AdapterHelper
-
-  require Logger
-
-  @defaults [pool: :federation]
-
-  @type ip_address :: ipv4_address() | ipv6_address()
-  @type ipv4_address :: {0..255, 0..255, 0..255, 0..255}
-  @type ipv6_address ::
-          {0..65_535, 0..65_535, 0..65_535, 0..65_535, 0..65_535, 0..65_535, 0..65_535, 0..65_535}
-  @type proxy_type() :: :socks4 | :socks5
-  @type host() :: charlist() | ip_address()
-
-  @doc """
-  Merge default connection & adapter options with received ones.
-  """
-
-  @spec options(URI.t(), keyword()) :: keyword()
-  def options(%URI{} = uri, opts \\ []) do
-    @defaults
-    |> pool_timeout()
-    |> Keyword.merge(opts)
-    |> adapter_helper().options(uri)
-  end
-
-  defp pool_timeout(opts) do
-    {config_key, default} =
-      if adapter() == Tesla.Adapter.Gun do
-        {:pools, Config.get([:pools, :default, :timeout])}
-      else
-        {:hackney_pools, 10_000}
-      end
-
-    timeout = Config.get([config_key, opts[:pool], :timeout], default)
-
-    Keyword.merge(opts, timeout: timeout)
-  end
-
-  @spec after_request(keyword()) :: :ok
-  def after_request(opts), do: adapter_helper().after_request(opts)
-
-  defp adapter, do: Application.get_env(:tesla, :adapter)
-
-  defp adapter_helper do
-    case adapter() do
-      Tesla.Adapter.Gun -> AdapterHelper.Gun
-      Tesla.Adapter.Hackney -> AdapterHelper.Hackney
-      _ -> AdapterHelper
-    end
-  end
-
-  @spec parse_proxy(String.t() | tuple() | nil) ::
-          {:ok, host(), pos_integer()}
-          | {:ok, proxy_type(), host(), pos_integer()}
-          | {:error, atom()}
-          | nil
-
-  def parse_proxy(nil), do: nil
-
-  def parse_proxy(proxy) when is_binary(proxy) do
-    with [host, port] <- String.split(proxy, ":"),
-         {port, ""} <- Integer.parse(port) do
-      {:ok, parse_host(host), port}
-    else
-      {_, _} ->
-        Logger.warn("Parsing port failed #{inspect(proxy)}")
-        {:error, :invalid_proxy_port}
-
-      :error ->
-        Logger.warn("Parsing port failed #{inspect(proxy)}")
-        {:error, :invalid_proxy_port}
-
-      _ ->
-        Logger.warn("Parsing proxy failed #{inspect(proxy)}")
-        {:error, :invalid_proxy}
-    end
-  end
-
-  def parse_proxy(proxy) when is_tuple(proxy) do
-    with {type, host, port} <- proxy do
-      {:ok, type, parse_host(host), port}
-    else
-      _ ->
-        Logger.warn("Parsing proxy failed #{inspect(proxy)}")
-        {:error, :invalid_proxy}
-    end
-  end
-
-  @spec parse_host(String.t() | atom() | charlist()) :: charlist() | ip_address()
-  def parse_host(host) when is_list(host), do: host
-  def parse_host(host) when is_atom(host), do: to_charlist(host)
-
-  def parse_host(host) when is_binary(host) do
-    host = to_charlist(host)
-
-    case :inet.parse_address(host) do
-      {:error, :einval} -> host
-      {:ok, ip} -> ip
-    end
-  end
-
-  @spec format_host(String.t()) :: charlist()
-  def format_host(host) do
-    host_charlist = to_charlist(host)
-
-    case :inet.parse_address(host_charlist) do
-      {:error, :einval} ->
-        :idna.encode(host_charlist)
-
-      {:ok, _ip} ->
-        host_charlist
-    end
-  end
-end

lib/pleroma/http/http.ex

@@ -7,7 +7,7 @@ defmodule Pleroma.HTTP do
     Wrapper for `Tesla.request/2`.
   """
 
-  alias Pleroma.HTTP.Connection
+  alias Pleroma.HTTP.AdapterHelper
   alias Pleroma.HTTP.Request
   alias Pleroma.HTTP.RequestBuilder, as: Builder
   alias Tesla.Client
@@ -60,49 +60,26 @@ def post(url, body, headers \\ [], options \\ []),
           {:ok, Env.t()} | {:error, any()}
   def request(method, url, body, headers, options) when is_binary(url) do
     uri = URI.parse(url)
-    adapter_opts = Connection.options(uri, options[:adapter] || [])
+    adapter_opts = AdapterHelper.options(uri, options[:adapter] || [])
-    options = put_in(options[:adapter], adapter_opts)
-    params = options[:params] || []
-    request = build_request(method, headers, options, url, body, params)
 
-    adapter = Application.get_env(:tesla, :adapter)
+    case AdapterHelper.get_conn(uri, adapter_opts) do
-    client = Tesla.client([Tesla.Middleware.FollowRedirects], adapter)
+      {:ok, adapter_opts} ->
+        options = put_in(options[:adapter], adapter_opts)
+        params = options[:params] || []
+        request = build_request(method, headers, options, url, body, params)
 
-    pid = Process.whereis(adapter_opts[:pool])
+        adapter = Application.get_env(:tesla, :adapter)
+        client = Tesla.client([Tesla.Middleware.FollowRedirects], adapter)
 
-    pool_alive? =
+        response = request(client, request)
-      if adapter == Tesla.Adapter.Gun && pid do
-        Process.alive?(pid)
-      else
-        false
-      end
 
-    request_opts =
+        AdapterHelper.after_request(adapter_opts)
-      adapter_opts
-      |> Enum.into(%{})
-      |> Map.put(:env, Pleroma.Config.get([:env]))
-      |> Map.put(:pool_alive?, pool_alive?)
 
-    response = request(client, request, request_opts)
+        response
 
-    Connection.after_request(adapter_opts)
+      err ->
-
+        err
-    response
+    end
-  end
-
-  @spec request(Client.t(), keyword(), map()) :: {:ok, Env.t()} | {:error, any()}
-  def request(%Client{} = client, request, %{env: :test}), do: request(client, request)
-
-  def request(%Client{} = client, request, %{body_as: :chunks}), do: request(client, request)
-
-  def request(%Client{} = client, request, %{pool_alive?: false}), do: request(client, request)
-
-  def request(%Client{} = client, request, %{pool: pool, timeout: timeout}) do
-    :poolboy.transaction(
-      pool,
-      &Pleroma.Pool.Request.execute(&1, client, request, timeout),
-      timeout
-    )
   end
 
   @spec request(Client.t(), keyword()) :: {:ok, Env.t()} | {:error, any()}

lib/pleroma/pool/connections.ex

@@ -1,283 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Pool.Connections do
-  use GenServer
-
-  alias Pleroma.Config
-  alias Pleroma.Gun
-
-  require Logger
-
-  @type domain :: String.t()
-  @type conn :: Pleroma.Gun.Conn.t()
-
-  @type t :: %__MODULE__{
-          conns: %{domain() => conn()},
-          opts: keyword()
-        }
-
-  defstruct conns: %{}, opts: []
-
-  @spec start_link({atom(), keyword()}) :: {:ok, pid()}
-  def start_link({name, opts}) do
-    GenServer.start_link(__MODULE__, opts, name: name)
-  end
-
-  @impl true
-  def init(opts), do: {:ok, %__MODULE__{conns: %{}, opts: opts}}
-
-  @spec checkin(String.t() | URI.t(), atom()) :: pid() | nil
-  def checkin(url, name)
-  def checkin(url, name) when is_binary(url), do: checkin(URI.parse(url), name)
-
-  def checkin(%URI{} = uri, name) do
-    timeout = Config.get([:connections_pool, :checkin_timeout], 250)
-
-    GenServer.call(name, {:checkin, uri}, timeout)
-  end
-
-  @spec alive?(atom()) :: boolean()
-  def alive?(name) do
-    if pid = Process.whereis(name) do
-      Process.alive?(pid)
-    else
-      false
-    end
-  end
-
-  @spec get_state(atom()) :: t()
-  def get_state(name) do
-    GenServer.call(name, :state)
-  end
-
-  @spec count(atom()) :: pos_integer()
-  def count(name) do
-    GenServer.call(name, :count)
-  end
-
-  @spec get_unused_conns(atom()) :: [{domain(), conn()}]
-  def get_unused_conns(name) do
-    GenServer.call(name, :unused_conns)
-  end
-
-  @spec checkout(pid(), pid(), atom()) :: :ok
-  def checkout(conn, pid, name) do
-    GenServer.cast(name, {:checkout, conn, pid})
-  end
-
-  @spec add_conn(atom(), String.t(), Pleroma.Gun.Conn.t()) :: :ok
-  def add_conn(name, key, conn) do
-    GenServer.cast(name, {:add_conn, key, conn})
-  end
-
-  @spec remove_conn(atom(), String.t()) :: :ok
-  def remove_conn(name, key) do
-    GenServer.cast(name, {:remove_conn, key})
-  end
-
-  @impl true
-  def handle_cast({:add_conn, key, conn}, state) do
-    state = put_in(state.conns[key], conn)
-
-    Process.monitor(conn.conn)
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_cast({:checkout, conn_pid, pid}, state) do
-    state =
-      with true <- Process.alive?(conn_pid),
-           {key, conn} <- find_conn(state.conns, conn_pid),
-           used_by <- List.keydelete(conn.used_by, pid, 0) do
-        conn_state = if used_by == [], do: :idle, else: conn.conn_state
-
-        put_in(state.conns[key], %{conn | conn_state: conn_state, used_by: used_by})
-      else
-        false ->
-          Logger.debug("checkout for closed conn #{inspect(conn_pid)}")
-          state
-
-        nil ->
-          Logger.debug("checkout for alive conn #{inspect(conn_pid)}, but is not in state")
-          state
-      end
-
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_cast({:remove_conn, key}, state) do
-    state = put_in(state.conns, Map.delete(state.conns, key))
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_call({:checkin, uri}, from, state) do
-    key = "#{uri.scheme}:#{uri.host}:#{uri.port}"
-
-    case state.conns[key] do
-      %{conn: pid, gun_state: :up} = conn ->
-        time = :os.system_time(:second)
-        last_reference = time - conn.last_reference
-        crf = crf(last_reference, 100, conn.crf)
-
-        state =
-          put_in(state.conns[key], %{
-            conn
-            | last_reference: time,
-              crf: crf,
-              conn_state: :active,
-              used_by: [from | conn.used_by]
-          })
-
-        {:reply, pid, state}
-
-      %{gun_state: :down} ->
-        {:reply, nil, state}
-
-      nil ->
-        {:reply, nil, state}
-    end
-  end
-
-  @impl true
-  def handle_call(:state, _from, state), do: {:reply, state, state}
-
-  @impl true
-  def handle_call(:count, _from, state) do
-    {:reply, Enum.count(state.conns), state}
-  end
-
-  @impl true
-  def handle_call(:unused_conns, _from, state) do
-    unused_conns =
-      state.conns
-      |> Enum.filter(&filter_conns/1)
-      |> Enum.sort(&sort_conns/2)
-
-    {:reply, unused_conns, state}
-  end
-
-  defp filter_conns({_, %{conn_state: :idle, used_by: []}}), do: true
-  defp filter_conns(_), do: false
-
-  defp sort_conns({_, c1}, {_, c2}) do
-    c1.crf <= c2.crf and c1.last_reference <= c2.last_reference
-  end
-
-  @impl true
-  def handle_info({:gun_up, conn_pid, _protocol}, state) do
-    %{origin_host: host, origin_scheme: scheme, origin_port: port} = Gun.info(conn_pid)
-
-    host =
-      case :inet.ntoa(host) do
-        {:error, :einval} -> host
-        ip -> ip
-      end
-
-    key = "#{scheme}:#{host}:#{port}"
-
-    state =
-      with {key, conn} <- find_conn(state.conns, conn_pid, key),
-           {true, key} <- {Process.alive?(conn_pid), key} do
-        put_in(state.conns[key], %{
-          conn
-          | gun_state: :up,
-            conn_state: :active,
-            retries: 0
-        })
-      else
-        {false, key} ->
-          put_in(
-            state.conns,
-            Map.delete(state.conns, key)
-          )
-
-        nil ->
-          :ok = Gun.close(conn_pid)
-
-          state
-      end
-
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_info({:gun_down, conn_pid, _protocol, _reason, _killed}, state) do
-    retries = Config.get([:connections_pool, :retry], 1)
-    # we can't get info on this pid, because pid is dead
-    state =
-      with {key, conn} <- find_conn(state.conns, conn_pid),
-           {true, key} <- {Process.alive?(conn_pid), key} do
-        if conn.retries == retries do
-          :ok = Gun.close(conn.conn)
-
-          put_in(
-            state.conns,
-            Map.delete(state.conns, key)
-          )
-        else
-          put_in(state.conns[key], %{
-            conn
-            | gun_state: :down,
-              retries: conn.retries + 1
-          })
-        end
-      else
-        {false, key} ->
-          put_in(
-            state.conns,
-            Map.delete(state.conns, key)
-          )
-
-        nil ->
-          Logger.debug(":gun_down for conn which isn't found in state")
-
-          state
-      end
-
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_info({:DOWN, _ref, :process, conn_pid, reason}, state) do
-    Logger.debug("received DOWN message for #{inspect(conn_pid)} reason -> #{inspect(reason)}")
-
-    state =
-      with {key, conn} <- find_conn(state.conns, conn_pid) do
-        Enum.each(conn.used_by, fn {pid, _ref} ->
-          Process.exit(pid, reason)
-        end)
-
-        put_in(
-          state.conns,
-          Map.delete(state.conns, key)
-        )
-      else
-        nil ->
-          Logger.debug(":DOWN for conn which isn't found in state")
-
-          state
-      end
-
-    {:noreply, state}
-  end
-
-  defp find_conn(conns, conn_pid) do
-    Enum.find(conns, fn {_key, conn} ->
-      conn.conn == conn_pid
-    end)
-  end
-
-  defp find_conn(conns, conn_pid, conn_key) do
-    Enum.find(conns, fn {key, conn} ->
-      key == conn_key and conn.conn == conn_pid
-    end)
-  end
-
-  def crf(current, steps, crf) do
-    1 + :math.pow(0.5, current / steps) * crf
-  end
-end

lib/pleroma/pool/pool.ex

@@ -1,22 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Pool do
-  def child_spec(opts) do
-    poolboy_opts =
-      opts
-      |> Keyword.put(:worker_module, Pleroma.Pool.Request)
-      |> Keyword.put(:name, {:local, opts[:name]})
-      |> Keyword.put(:size, opts[:size])
-      |> Keyword.put(:max_overflow, opts[:max_overflow])
-
-    %{
-      id: opts[:id] || {__MODULE__, make_ref()},
-      start: {:poolboy, :start_link, [poolboy_opts, [name: opts[:name]]]},
-      restart: :permanent,
-      shutdown: 5000,
-      type: :worker
-    }
-  end
-end

lib/pleroma/pool/request.ex

@@ -1,65 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Pool.Request do
-  use GenServer
-
-  require Logger
-
-  def start_link(args) do
-    GenServer.start_link(__MODULE__, args)
-  end
-
-  @impl true
-  def init(_), do: {:ok, []}
-
-  @spec execute(pid() | atom(), Tesla.Client.t(), keyword(), pos_integer()) ::
-          {:ok, Tesla.Env.t()} | {:error, any()}
-  def execute(pid, client, request, timeout) do
-    GenServer.call(pid, {:execute, client, request}, timeout)
-  end
-
-  @impl true
-  def handle_call({:execute, client, request}, _from, state) do
-    response = Pleroma.HTTP.request(client, request)
-
-    {:reply, response, state}
-  end
-
-  @impl true
-  def handle_info({:gun_data, _conn, _stream, _, _}, state) do
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_info({:gun_up, _conn, _protocol}, state) do
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_info({:gun_down, _conn, _protocol, _reason, _killed}, state) do
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_info({:gun_error, _conn, _stream, _error}, state) do
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_info({:gun_push, _conn, _stream, _new_stream, _method, _uri, _headers}, state) do
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_info({:gun_response, _conn, _stream, _, _status, _headers}, state) do
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_info(msg, state) do
-    Logger.warn("Received unexpected message #{inspect(__MODULE__)} #{inspect(msg)}")
-    {:noreply, state}
-  end
-end

lib/pleroma/pool/supervisor.ex

@@ -1,42 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Pool.Supervisor do
-  use Supervisor
-
-  alias Pleroma.Config
-  alias Pleroma.Pool
-
-  def start_link(args) do
-    Supervisor.start_link(__MODULE__, args, name: __MODULE__)
-  end
-
-  def init(_) do
-    conns_child = %{
-      id: Pool.Connections,
-      start:
-        {Pool.Connections, :start_link, [{:gun_connections, Config.get([:connections_pool])}]}
-    }
-
-    Supervisor.init([conns_child | pools()], strategy: :one_for_one)
-  end
-
-  defp pools do
-    pools = Config.get(:pools)
-
-    pools =
-      if Config.get([Pleroma.Upload, :proxy_remote]) == false do
-        Keyword.delete(pools, :upload)
-      else
-        pools
-      end
-
-    for {pool_name, pool_opts} <- pools do
-      pool_opts
-      |> Keyword.put(:id, {Pool, pool_name})
-      |> Keyword.put(:name, pool_name)
-      |> Pool.child_spec()
-    end
-  end
-end

lib/pleroma/reverse_proxy/client/tesla.ex

@@ -48,7 +48,7 @@ def stream_body(%{pid: pid, opts: opts, fin: true}) do
     # if there were redirects we need to checkout old conn
     conn = opts[:old_conn] || opts[:conn]
 
-    if conn, do: :ok = Pleroma.Pool.Connections.checkout(conn, self(), :gun_connections)
+    if conn, do: :ok = Pleroma.Gun.ConnectionPool.release_conn(conn)
 
     :done
   end