Add an API to await for node startup from a remote node.

rabbitmqctl wait will have more flexibility if the rabbitmqctl node
will do the waiting. For example when net_ticktime is lower than
startup time wait would not fail.

Author: Daniil Fedotov

src/rabbit.erl

@@ -19,7 +19,8 @@
 -behaviour(application).
 
 -export([start/0, boot/0, stop/0,
-         stop_and_halt/0, await_startup/0, status/0, is_running/0, alarms/0,
+         stop_and_halt/0, await_startup/0, await_startup/1,
+         status/0, is_running/0, alarms/0,
          is_running/1, environment/0, rotate_logs/0, force_event_refresh/1,
          start_fhc/0]).
 -export([start/2, stop/1, prep_stop/1]).
@@ -473,7 +474,7 @@ stop() ->
         undefined -> ok;
         _         ->
             rabbit_log:info("RabbitMQ hasn't finished starting yet. Waiting for startup to finish before stopping..."),
-            wait_for_boot_to_finish()
+            ok = wait_for_boot_to_finish(node())
     end,
     rabbit_log:info("RabbitMQ is asked to stop...~n", []),
     Apps = ?APPS ++ rabbit_plugins:active(),
@@ -647,32 +648,52 @@ handle_app_error(Term) ->
     end.
 
 await_startup() ->
-    case is_booting() of
-        true -> wait_for_boot_to_finish();
+    await_startup(node()).
+
+await_startup(Node) ->
+    case is_booting(Node) of
+        true -> wait_for_boot_to_finish(Node);
         false ->
-            case is_running() of
+            case is_running(Node) of
                 true -> ok;
-                false -> wait_for_boot_to_start(),
-                         wait_for_boot_to_finish()
+                false -> wait_for_boot_to_start(Node),
+                         wait_for_boot_to_finish(Node)
             end
     end.
 
-is_booting() ->
-    whereis(rabbit_boot) /= undefined.
+is_booting(Node) ->
+    case rpc:call(Node, erlang, whereis, [rabbit_boot]) of
+        {badrpc, _} = Err -> Err;
+        undefined         -> false;
+        P when is_pid(P)  -> true
+    end.
 
-wait_for_boot_to_start() ->
-    case whereis(rabbit_boot) of
-        undefined -> timer:sleep(100),
-                     wait_for_boot_to_start();
-        _         -> ok
+wait_for_boot_to_start(Node) ->
+    case is_booting(Node) of
+        false ->
+            timer:sleep(100),
+            wait_for_boot_to_start(Node);
+        {badrpc, _} = Err ->
+            Err;
+        true  ->
+            ok
     end.
 
-wait_for_boot_to_finish() ->
-    case whereis(rabbit_boot) of
-        undefined -> true = is_running(),
-                     ok;
-        _         -> timer:sleep(100),
-                     wait_for_boot_to_finish()
+wait_for_boot_to_finish(Node) ->
+    case is_booting(Node) of
+        false ->
+            %% We don't want badrpc error to be interpreted as false,
+            %% so we don't call rabbit:is_running(Node)
+            case rpc:call(Node, rabbit, is_running, []) of
+                true              -> ok;
+                false             -> {error, rabbit_is_not_running};
+                {badrpc, _} = Err -> Err
+            end;
+        {badrpc, _} = Err ->
+            Err;
+        true  ->
+            timer:sleep(100),
+            wait_for_boot_to_finish(Node)
     end.
 
 status() ->