haproxy: properly close socket after query

lib/ha_handler/control.ex

@@ -70,7 +70,7 @@ defmodule HAHandler.Control do
 				{:secondary, "MAINT"} ->
 					:noop
 				unknown ->
-					Logger.warning("Unhandled PGSQL/HAProxy state: #{unknown}")
+					Logger.warning("Unhandled PGSQL/HAProxy state: #{inspect(unknown)}")
 			end
 		end
 

lib/ha_handler/ha_proxy.ex

@@ -26,9 +26,13 @@ defmodule HAHandler.HAProxy do
   """
   def execute(command) when is_binary(command) do
     case open_socket(haproxy_socket()) do
-      {:ok, socket} ->
-        send(socket, {self(), {:command, command <> "\n"}})
-        read_from_socket(socket)
+      {:ok, fd, port} ->
+        send(port, {self(), {:command, command <> "\n"}})
+        data = read_from_socket(port)
+        # We need to be careful and always close file descriptors, as they can
+        # run out - which will block all operations.
+        close_socket(fd)
+        data
       {:error, err} ->
         {:error, err}
     end
@@ -158,13 +162,16 @@ defmodule HAHandler.HAProxy do
         {fdin, fdout} = {socket, socket}
         port = Port.open({:fd, fdin, fdout}, [{:line, 10_000}, :binary])
 
-        {:ok, port}
+        {:ok, socket, port}
 
       {:error, err} ->
         {:error, err}
     end
   end
 
+  # Close UNIX fd opened with `open_socket/1`.
+  defp close_socket(fd), do: Socket.close(fd)
+
   # Messages may be split due to the `{:line, L}` option specific in
   # `open_socket/1`.
   defp read_from_socket(socket, acc \\ "") do