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

1 files changed, 4 insertions, 4 deletions

diff --git a/lib/pleroma/application.ex b/lib/pleroma/application.ex
index 3282c6882..be14c1f9f 100644
--- a/lib/pleroma/application.ex
+++ b/lib/pleroma/application.ex
@@ -223,9 +223,7 @@ defmodule Pleroma.Application do
 
   # start hackney and gun pools in tests
   defp http_children(_, :test) do
-    hackney_options = Config.get([:hackney_pools, :federation])
-    hackney_pool = :hackney_pool.child_spec(:federation, hackney_options)
-    [hackney_pool, Pleroma.Pool.Supervisor]
+    http_children(Tesla.Adapter.Hackney, nil) ++ http_children(Tesla.Adapter.Gun, nil)
   end
 
   defp http_children(Tesla.Adapter.Hackney, _) do
@@ -244,7 +242,9 @@ defmodule Pleroma.Application 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