let `rabbit_alarm' handle everything in place of `alarm_handler'

No logging on set/clear alarm yet, me and Simon agree that we should do
logging only on the events that rabbit knows it should be receiving
(right now the resource limits ones)

5 files changed, 34 insertions, 21 deletions

diff --git a/Makefile b/Makefile
index 0e3960dcfa..3681a7878d 100644
--- a/Makefile
+++ b/Makefile
@@ -217,11 +217,11 @@ stop-rabbit-on-node: all
 	echo "rabbit:stop()." | $(ERL_CALL)
 
 set-resource-alarm: all
-	echo "alarm_handler:set_alarm({{resource_limit, $(SOURCE), node()}, []})." | \
+	echo "rabbit_alarm:set_alarm({{resource_limit, $(SOURCE), node()}, []})." | \
 	$(ERL_CALL)
 
 clear-resource-alarm: all
-	echo "alarm_handler:clear_alarm({resource_limit, $(SOURCE), node()})." | \
+	echo "rabbit_alarm:clear_alarm({resource_limit, $(SOURCE), node()})." | \
 	$(ERL_CALL)
 
 stop-node:
diff --git a/src/file_handle_cache.erl b/src/file_handle_cache.erl
index f3b4dbafa2..2546d5c5d6 100644
--- a/src/file_handle_cache.erl
+++ b/src/file_handle_cache.erl
@@ -1028,8 +1028,8 @@ obtain_limit_reached(#fhc_state { obtain_limit = Limit,
 
 adjust_alarm(OldState, NewState) ->
     case {obtain_limit_reached(OldState), obtain_limit_reached(NewState)} of
-        {false, true} -> alarm_handler:set_alarm({file_descriptor_limit, []});
-        {true, false} -> alarm_handler:clear_alarm(file_descriptor_limit);
+        {false, true} -> rabbit_alarm:set_alarm({file_descriptor_limit, []});
+        {true, false} -> rabbit_alarm:clear_alarm(file_descriptor_limit);
         _             -> ok
     end,
     NewState.
diff --git a/src/rabbit_alarm.erl b/src/rabbit_alarm.erl
index d16d90a45d..1fb2056e74 100644
--- a/src/rabbit_alarm.erl
+++ b/src/rabbit_alarm.erl
@@ -18,19 +18,23 @@
 
 -behaviour(gen_event).
 
--export([start/0, stop/0, register/2, on_node_up/1, on_node_down/1]).
+-export([start_link/0, start/0, stop/0, register/2, set_alarm/1,
+         clear_alarm/1, on_node_up/1, on_node_down/1]).
 
 -export([init/1, handle_call/2, handle_event/2, handle_info/2,
          terminate/2, code_change/3]).
 
 -export([remote_conserve_resources/3]). %% Internal use only
 
+-define(SERVER, ?MODULE).
+
 -record(alarms, {alertees, alarmed_nodes}).
 
 %%----------------------------------------------------------------------------
 
 -ifdef(use_specs).
 
+-spec(start_link/0 :: () -> rabbit_types:ok_pid_or_error()).
 -spec(start/0 :: () -> 'ok').
 -spec(stop/0 :: () -> 'ok').
 -spec(register/2 :: (pid(), rabbit_types:mfargs()) -> boolean()).
@@ -41,36 +45,43 @@
 
 %%----------------------------------------------------------------------------
 
+start_link() ->
+    gen_event:start_link({local, ?SERVER}).
+
 start() ->
-    ok = alarm_handler:add_alarm_handler(?MODULE, []),
+    ok = rabbit_sup:start_restartable_child(?MODULE),
+    ok = gen_event:add_handler(?SERVER, ?MODULE, []),
     {ok, MemoryWatermark} = application:get_env(vm_memory_high_watermark),
     rabbit_sup:start_restartable_child(vm_memory_monitor, [MemoryWatermark]),
-
     {ok, DiskLimit} = application:get_env(disk_free_limit),
     rabbit_sup:start_restartable_child(rabbit_disk_monitor, [DiskLimit]),
     ok.
 
 stop() ->
-    ok = alarm_handler:delete_alarm_handler(?MODULE).
+    ok.
 
 register(Pid, HighMemMFA) ->
-    gen_event:call(alarm_handler, ?MODULE,
-                   {register, Pid, HighMemMFA},
+    gen_event:call(?SERVER, ?MODULE, {register, Pid, HighMemMFA},
                    infinity).
 
-on_node_up(Node) -> gen_event:notify(alarm_handler, {node_up, Node}).
+set_alarm(Alarm) ->
+    gen_event:notify(?SERVER, {set_alarm, Alarm}).
 
-on_node_down(Node) -> gen_event:notify(alarm_handler, {node_down, Node}).
+clear_alarm(Alarm) ->
+    gen_event:notify(?SERVER, {clear_alarm, Alarm}).
+
+on_node_up(Node) -> gen_event:notify(?SERVER, {node_up, Node}).
+
+on_node_down(Node) -> gen_event:notify(?SERVER, {node_down, Node}).
 
-%% Can't use alarm_handler:{set,clear}_alarm because that doesn't
-%% permit notifying a remote node.
 remote_conserve_resources(Pid, Source, true) ->
-    gen_event:notify({alarm_handler, node(Pid)},
+    gen_event:notify({?SERVER, node(Pid)},
                      {set_alarm, {{resource_limit, Source, node()}, []}});
 remote_conserve_resources(Pid, Source, false) ->
-    gen_event:notify({alarm_handler, node(Pid)},
+    gen_event:notify({?SERVER, node(Pid)},
                      {clear_alarm, {resource_limit, Source, node()}}).
 
+
 %%----------------------------------------------------------------------------
 
 init([]) ->
@@ -85,15 +96,17 @@ handle_call(_Request, State) ->
     {ok, not_understood, State}.
 
 handle_event({set_alarm, {{resource_limit, Source, Node}, []}}, State) ->
+    %% TODO: Do some logging
     {ok, maybe_alert(fun dict:append/3, Node, Source, State)};
 
 handle_event({clear_alarm, {resource_limit, Source, Node}}, State) ->
+    %% TODO: Do some logging
     {ok, maybe_alert(fun dict_unappend/3, Node, Source, State)};
 
 handle_event({node_up, Node}, State) ->
     %% Must do this via notify and not call to avoid possible deadlock.
     ok = gen_event:notify(
-           {alarm_handler, Node},
+           {?SERVER, Node},
            {register, self(), {?MODULE, remote_conserve_resources, []}}),
     {ok, State};
 
diff --git a/src/rabbit_disk_monitor.erl b/src/rabbit_disk_monitor.erl
index 58375abb45..e72181c061 100644
--- a/src/rabbit_disk_monitor.erl
+++ b/src/rabbit_disk_monitor.erl
@@ -149,10 +149,10 @@ internal_update(State = #state { limit   = Limit,
     case {Alarmed, NewAlarmed} of
         {false, true} ->
             emit_update_info("exceeded", CurrentFreeBytes, LimitBytes),
-            alarm_handler:set_alarm({{resource_limit, disk, node()}, []});
+            rabbit_alarm:set_alarm({{resource_limit, disk, node()}, []});
         {true, false} ->
             emit_update_info("below limit", CurrentFreeBytes, LimitBytes),
-            alarm_handler:clear_alarm({resource_limit, disk, node()});
+            rabbit_alarm:clear_alarm({resource_limit, disk, node()});
         _ ->
             ok
     end,
diff --git a/src/vm_memory_monitor.erl b/src/vm_memory_monitor.erl
index fb184d1ab2..3f34c2e9e0 100644
--- a/src/vm_memory_monitor.erl
+++ b/src/vm_memory_monitor.erl
@@ -181,10 +181,10 @@ internal_update(State = #state { memory_limit = MemLimit,
     case {Alarmed, NewAlarmed} of
         {false, true} ->
             emit_update_info(set, MemUsed, MemLimit),
-            alarm_handler:set_alarm({{resource_limit, memory, node()}, []});
+            rabbit_alarm:set_alarm({{resource_limit, memory, node()}, []});
         {true, false} ->
             emit_update_info(clear, MemUsed, MemLimit),
-            alarm_handler:clear_alarm({resource_limit, memory, node()});
+            rabbit_alarm:clear_alarm({resource_limit, memory, node()});
         _ ->
             ok
     end,