defer starting gun to handle_continue so init is fast

Author: rnewson

src/nouveau/src/nouveau_gun.erl

@@ -29,6 +29,7 @@
 -export([handle_call/3]).
 -export([handle_cast/2]).
 -export([handle_info/2]).
+-export([handle_continue/2]).
 
 % config_listener callbacks
 -export([handle_config_change/5]).
@@ -44,27 +45,26 @@ host_header() ->
 
 init(_) ->
     URL = nouveau_util:nouveau_url(),
-    case start_gun(URL) of
-        {ok, _PoolPid} ->
-            ok = config:listen_for_changes(?MODULE, URL),
-            {ok, nil};
-        {error, Reason} ->
-            {error, Reason}
-    end.
+    ok = config:listen_for_changes(?MODULE, URL),
+    {ok, URL, {continue, start_gun}}.
 
 handle_call(_Msg, _From, State) ->
     {reply, unexpected_msg, State}.
 
 handle_cast(_Msg, State) ->
     {noreply, State}.
 
-handle_info(restart_config_listener, State) ->
-    ok = config:listen_for_changes(?MODULE, nil),
-    {noreply, State};
-handle_info(Msg, State) ->
-    couch_log:warning("~p received unexpected message: ~p", [?MODULE, Msg]),
+handle_info(_Msg, State) ->
     {noreply, State}.
 
+handle_continue(start_gun, URL) ->
+    case start_gun(URL) of
+        {ok, _ManagerPid} ->
+            {noreply, URL};
+        {error, Reason} ->
+            {stop, Reason}
+    end.
+
 handle_config_change("nouveau", "url", URL, _Persist, OldURL) ->
     case start_gun(URL) of
         {ok, _PoolPid} ->