Fix case where acceptors shut down forever after max_connections is hit

lib/thousand_island/acceptor.ex

@@ -28,6 +28,7 @@ defmodule ThousandIsland.Acceptor do
     else
       {:error, :too_many_connections} ->
         ThousandIsland.Telemetry.span_event(span, :spawn_error)
+        accept(listener_socket, connection_sup_pid, server_config, span, count + 1)
 
       {:error, reason} when reason in [:closed, :einval, :econnaborted] ->
         ThousandIsland.Telemetry.stop_span(span, %{connections: count})

test/thousand_island/server_test.exs

@@ -134,6 +134,20 @@ defmodule ThousandIsland.ServerTest do
       assert :gen_tcp.recv(client, 0) == {:ok, ~c"HELLO"}
       assert :gen_tcp.recv(other_client, 0) == {:error, :closed}
       :gen_tcp.close(other_client)
+
+      # Close the first connection and ensure new connections are now accepted
+      :gen_tcp.close(client)
+
+      # Give things enough time for the first connection to time out
+      Process.sleep(500)
+
+      {:ok, third_client} = :gen_tcp.connect(:localhost, port, active: false)
+      :ok = :gen_tcp.send(third_client, "BUONGIORNO")
+
+      # Give things enough time to send if they were going to
+      Process.sleep(100)
+
+      assert :gen_tcp.recv(third_client, 0) == {:ok, ~c"BUONGIORNO"}
     end
 
     test "should emit telemetry events as expected" do