Reload apps on config update.

Configuration update requires applications to be unloaded.
Some of the rabbit dependencies are loaded on VM boot, so they
should be unloaded before config update.
Applications which are already running during config update cannot be
unloaded (e.g. kernel) and warning should be reported that config
cannot be applied to these applications

1 files changed, 31 insertions, 7 deletions

diff --git a/src/rabbit_config.erl b/src/rabbit_config.erl
index 67e7523ec0..9e70898c82 100644
--- a/src/rabbit_config.erl
+++ b/src/rabbit_config.erl
@@ -33,10 +33,10 @@ prepare_and_use_config() ->
 legacy_erlang_term_config_used() ->
     case init:get_argument(config) of
         error        -> false;
-        {ok, [Config | _]} -> 
+        {ok, [Config | _]} ->
             ConfigFile = Config ++ ".config",
-            rabbit_file:is_file(ConfigFile) 
-            andalso 
+            rabbit_file:is_file(ConfigFile)
+            andalso
             get_advanced_config() == none
     end.
 
@@ -66,10 +66,34 @@ prepare_config(Configs) ->
     end.
 
 update_app_config(ConfigFile) ->
-    ok = application_controller:change_application_data([], [ConfigFile]).
+    RunningApps = [ App || {App, _, _} <- application:which_applications() ],
+    LoadedApps = [ App || {App, _, _} <- application:loaded_applications() ],
+    {ok, [Config]} = file:consult(ConfigFile),
+    %% For application config to be updated, applications should
+    %% be unloaded first.
+    %% If an application is already running, print an error.
+    lists:foreach(fun({App, _Config}) ->
+        case lists:member(App, RunningApps) of
+            true ->
+                io:format(standard_error,
+                          "~nUnable to update config for app ~p from *.conf file."
+                          " App is already running. Use advanced.config instead.~n",
+                          [App]);
+            false ->
+                case lists:member(App, LoadedApps) of
+                    true  -> application:unload(App);
+                    false -> ok
+                end
+        end
+    end,
+    Config),
+    ok = application_controller:change_application_data([], [ConfigFile]),
+    %% Make sure to load all the applications we're unloaded
+    lists:foreach(fun(App) -> application:load(App) end, LoadedApps),
+    ok.
 
 generate_config_file(ConfFiles, ConfDir, ScriptDir) ->
-    generate_config_file(ConfFiles, ConfDir, ScriptDir, 
+    generate_config_file(ConfFiles, ConfDir, ScriptDir,
                          schema_dir(), get_advanced_config()).
 
 
@@ -145,8 +169,8 @@ config_files() ->
                 {ok, Files} -> [Abs(File, ".config") || [File] <- Files];
                 error       -> case config_setting() of
                                    none -> [];
-                                   File -> [Abs(File, ".config") 
-                                            ++ 
+                                   File -> [Abs(File, ".config")
+                                            ++
                                             " (not found)"]
                                end
             end;