Add autocluster lock

src/emqttd_app.erl

@@ -149,23 +149,41 @@ register_acl_mod() ->
 %%--------------------------------------------------------------------
 
 start_autocluster() ->
+    case application:get_env(?APP, autocluster_lock) of
+        undefined ->
+            application:set_env(?APP, autocluster_lock, true),
             ekka:callback(prepare, fun emqttd:shutdown/1),
             ekka:callback(reboot,  fun emqttd:reboot/0),
-    Fun = fun() -> ekka_autocluster:start(fun after_autocluster/0) end,
+            run_outside_application({ekka_autocluster, start, [fun after_autocluster/0]});
-    run_outside_application(5000, Fun).
+        {ok, _Lock} ->
+            ignore
+    end.
 
 after_autocluster() ->
     emqttd_plugins:init(),
     emqttd_plugins:load(),
     start_listeners().
 
-run_outside_application(Delay, Callback) ->
+run_outside_application({M, F, Args}) ->
     spawn(fun() ->
             group_leader(whereis(init), self()),
-            timer:sleep(Delay),
+            wait_app_ready(5),
-            Callback()
+            try erlang:apply(M, F, Args)
+            catch
+                _:Error -> lager:error("Autocluster exception: ~p", [Error])
+            end,
+            application:unset_env(?APP, autocluster_lock)
           end).
 
+wait_app_ready(0) ->
+    timeout;
+wait_app_ready(Retries) ->
+    case lists:keymember(?APP, 1, application:which_applications()) of
+        true  -> ok;
+        false -> timer:sleep(1000),
+                 wait_app_ready(Retries - 1)
+    end.
+
 %%--------------------------------------------------------------------
 %% Start Listeners
 %%--------------------------------------------------------------------