implement deletion of guarded handlers

src/riak_core.erl

@@ -23,7 +23,7 @@
 -export([stop/0, stop/1]).
 -export([register_vnode_module/1, vnode_modules/0]).
 -export([add_guarded_event_handler/3, add_guarded_event_handler/4]).
-
+-export([delete_guarded_event_handler/3]).
 
 %% @spec stop() -> ok
 %% @doc Stop the riak application and the calling process.
@@ -76,6 +76,25 @@ add_guarded_event_handler(HandlerMod, Handler, Args) ->
 add_guarded_event_handler(HandlerMod, Handler, Args, ExitFun) ->
     riak_core_eventhandler_sup:start_guarded_handler(HandlerMod, Handler, Args, ExitFun).
 
+%% @spec delete_guarded_event_handler(HandlerMod, Handler, Args) -> Result
+%%       HandlerMod = module()
+%%       Handler = module() | {module(), term()}
+%%       Args = term()
+%%       Result = term() | {error, module_not_found} | {'EXIT', Reason}
+%%       Reason = term()
+%%
+%% @doc Delete a guarded event handler from a gen_event instance.
+%% 
+%%      Args is an arbitrary term which is passed as one of the arguments to 
+%%      Module:terminate/2.
+%%
+%%      The return value is the return value of Module:terminate/2. If the 
+%%      specified event handler is not installed, the function returns 
+%%      {error,module_not_found}. If the callback function fails with Reason, 
+%%      the function returns {'EXIT',Reason}.
+delete_guarded_event_handler(HandlerMod, Handler, Args) ->
+    riak_core_eventhandler_sup:stop_guarded_handler(HandlerMod, Handler, Args).
+
 app_for_module(Mod) ->
     app_for_module(application:which_applications(), Mod).
 

src/riak_core_eventhandler_guard.erl

@@ -42,14 +42,14 @@ handle_cast(_Msg, State) -> {noreply, State}.
 
 
 handle_info({gen_event_EXIT, _Handler, shutdown}, State) ->
-    {stop, shutdown, State};
-handle_info({gen_event_EXIT, _Handler, normal}, State) ->
     {stop, normal, State};
-handle_info({gen_event_EXIT, _Handler, _Reason}, State=#state{exitfun=undefined}) ->
+handle_info({gen_event_EXIT, _Handler, normal}, State) ->
     {stop, normal, State};
+handle_info({gen_event_EXIT, Handler, _Reason}, State=#state{exitfun=undefined}) ->
+    {stop, {gen_event_EXIT, Handler}, State};
 handle_info({gen_event_EXIT, Handler, Reason}, State=#state{exitfun=ExitFun}) ->
     ExitFun(Handler, Reason),
-    {stop, normal, State};
+    {stop, {gen_event_EXIT, Handler}, State};
 handle_info(_Info, State) ->
     {noreply, State}.
 
@@ -58,7 +58,3 @@ terminate(_Reason, #state{}) ->
 
 code_change(_OldVsn, State, _Extra) -> {ok, State}.
 
-%default_exitfun(Handler, _Reason) ->
-%    error_logger:error_msg(" ~s: handler ~w exited",
-%                           [?MODULE, Handler]).
-

src/riak_core_eventhandler_sup.erl

@@ -24,7 +24,7 @@
 -module(riak_core_eventhandler_sup).
 -behaviour(supervisor).
 -export([start_link/0, init/1]).
--export([start_guarded_handler/3, start_guarded_handler/4]).
+-export([start_guarded_handler/3, start_guarded_handler/4, stop_guarded_handler/3]).
 
 start_guarded_handler(HandlerMod, Handler, Args) ->
     start_guarded_handler(HandlerMod, Handler, Args, undefined).
@@ -35,10 +35,26 @@ start_guarded_handler(HandlerMod, Handler, Args, ExitFun) ->
         Other -> Other
     end.
 
+stop_guarded_handler(HandlerMod, Handler, Args) ->
+    case lists:member(Handler, gen_event:which_handlers(HandlerMod)) of
+        true ->
+            case gen_event:delete_handler(HandlerMod, Handler, Args) of
+                {error, module_not_found} ->
+                    {error, module_not_found};
+                O ->
+                    Id = {HandlerMod, Handler},
+                    ok = supervisor:terminate_child(?MODULE, Id),
+                    ok = supervisor:delete_child(?MODULE, Id),
+                    O
+            end;
+        false ->
+            {error, module_not_found}
+    end.
+
 handler_spec(HandlerMod, Handler, Args, ExitFun) ->
     {{HandlerMod, Handler},
      {riak_core_eventhandler_guard, start_link, [HandlerMod, Handler, Args, ExitFun]},
-     permanent, 5000, worker, [riak_core_eventhandler_guard]}.
+     transient, 5000, worker, [riak_core_eventhandler_guard]}.
 
 start_link() ->
     supervisor:start_link({local, ?MODULE}, ?MODULE, []).

test/test_guarded_event_handler.erl

@@ -50,8 +50,8 @@ handle_call(get_events, State) ->
 handle_info(_Info, State) ->
     {ok, State}.
 
-terminate(_Reason, _State) ->
-    ok.
+terminate(Reason, _State) ->
+    Reason.
 
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
@@ -76,6 +76,14 @@ cleanup(_Pid) ->
     process_flag(trap_exit, true),
     gen_event:stop(?MODULE).
 
+wait_for_exitfun() ->
+    receive 
+        {?MODULE, {'EXIT', crash}} ->
+            ok
+    after 5000 ->
+            fail
+    end.
+
 guarded_handler_test_case() ->
     Self = self(),
     F = fun(Handler, Reason) ->
@@ -85,17 +93,13 @@ guarded_handler_test_case() ->
     gen_event:notify(?MODULE, {event, foo}),
     ?assertEqual(?MODULE:get_events(), [foo]),
     gen_event:notify(?MODULE, crash),
-    Res = receive 
-              {?MODULE, {'EXIT', crash}} ->
-                  ok
-              after 5000 ->
-                  fail
-              end,
-    ?assertEqual(Res, ok),
+    ?assertEqual(wait_for_exitfun(), ok),
     wait_for_handler(?MODULE, 1000, 100),
     gen_event:notify(?MODULE, {event, baz}),
-    Events2 = ?MODULE:get_events(),
-    ?assertEqual(Events2, [baz]).
+    ?assertEqual(?MODULE:get_events(), [baz]),
+    ?assertEqual(riak_core:delete_guarded_event_handler(?MODULE,?MODULE,quux), quux),
+    ?assertNot(lists:member(?MODULE, gen_event:which_handlers(?MODULE))),
+    ?assertEqual([], supervisor:which_children(riak_core_eventhandler_sup)).
 
 wait_for_handler(_, 0, _) ->
     fail;