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%% The contents of this file are subject to the Mozilla Public License
%% Version 1.1 (the "License"); you may not use this file except in
%% compliance with the License. You may obtain a copy of the License
%% at http://www.mozilla.org/MPL/
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and
%% limitations under the License.
%%
%% The Original Code is RabbitMQ.
%%
%% The Initial Developer of the Original Code is VMware, Inc.
%% Copyright (c) 2007-2012 VMware, Inc. All rights reserved.
%%
-module(rabbit_alarm).
-behaviour(gen_event).
-export([start_link/0, start/0, stop/0, register/2, set_alarm/1,
clear_alarm/1, get_alarms/0, 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, alarms}).
%%----------------------------------------------------------------------------
-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()).
-spec(set_alarm/1 :: (any()) -> 'ok').
-spec(clear_alarm/1 :: (any()) -> 'ok').
-spec(on_node_up/1 :: (node()) -> 'ok').
-spec(on_node_down/1 :: (node()) -> 'ok').
-endif.
%%----------------------------------------------------------------------------
start_link() ->
gen_event:start_link({local, ?SERVER}).
start() ->
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, fun rabbit_alarm:set_alarm/1,
fun rabbit_alarm:clear_alarm/1]),
{ok, DiskLimit} = application:get_env(disk_free_limit),
rabbit_sup:start_restartable_child(rabbit_disk_monitor, [DiskLimit]),
ok.
stop() -> ok.
register(Pid, HighMemMFA) ->
gen_event:call(?SERVER, ?MODULE, {register, Pid, HighMemMFA},
infinity).
set_alarm(Alarm) -> gen_event:notify(?SERVER, {set_alarm, Alarm}).
clear_alarm(Alarm) -> gen_event:notify(?SERVER, {clear_alarm, Alarm}).
get_alarms() -> gen_event:call(?SERVER, ?MODULE, get_alarms, infinity).
on_node_up(Node) -> gen_event:notify(?SERVER, {node_up, Node}).
on_node_down(Node) -> gen_event:notify(?SERVER, {node_down, Node}).
remote_conserve_resources(Pid, Source, true) ->
gen_event:notify({?SERVER, node(Pid)},
{set_alarm, {{resource_limit, Source, node()}, []}});
remote_conserve_resources(Pid, Source, false) ->
gen_event:notify({?SERVER, node(Pid)},
{clear_alarm, {resource_limit, Source, node()}}).
%%----------------------------------------------------------------------------
init([]) ->
{ok, #alarms{alertees = dict:new(),
alarmed_nodes = dict:new(),
alarms = []}}.
handle_call({register, Pid, HighMemMFA}, State) ->
{ok, 0 < dict:size(State#alarms.alarmed_nodes),
internal_register(Pid, HighMemMFA, State)};
handle_call(get_alarms, State = #alarms{alarms = Alarms}) ->
{ok, Alarms, State};
handle_call(_Request, State) ->
{ok, not_understood, State}.
handle_event({set_alarm, Alarm}, State = #alarms{alarms = Alarms}) ->
handle_set_alarm(Alarm, State#alarms{alarms = [Alarm|Alarms]});
handle_event({clear_alarm, Alarm}, State = #alarms{alarms = Alarms}) ->
handle_clear_alarm(Alarm, State#alarms{alarms = lists:keydelete(Alarm, 1,
Alarms)});
handle_event({node_up, Node}, State) ->
%% Must do this via notify and not call to avoid possible deadlock.
ok = gen_event:notify(
{?SERVER, Node},
{register, self(), {?MODULE, remote_conserve_resources, []}}),
{ok, State};
handle_event({node_down, Node}, State) ->
{ok, maybe_alert(fun dict_unappend_all/3, Node, [], State)};
handle_event({register, Pid, HighMemMFA}, State) ->
{ok, internal_register(Pid, HighMemMFA, State)};
handle_event(_Event, State) ->
{ok, State}.
handle_info({'DOWN', _MRef, process, Pid, _Reason},
State = #alarms{alertees = Alertees}) ->
{ok, State#alarms{alertees = dict:erase(Pid, Alertees)}};
handle_info(_Info, State) ->
{ok, State}.
terminate(_Arg, _State) ->
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
%%----------------------------------------------------------------------------
dict_unappend_all(Key, _Val, Dict) ->
dict:erase(Key, Dict).
dict_unappend(Key, Val, Dict) ->
case lists:delete(Val, dict:fetch(Key, Dict)) of
[] -> dict:erase(Key, Dict);
X -> dict:store(Key, X, Dict)
end.
count_dict_values(Val, Dict) ->
dict:fold(fun (_Node, List, Count) ->
Count + case lists:member(Val, List) of
true -> 1;
false -> 0
end
end, 0, Dict).
maybe_alert(UpdateFun, Node, Source,
State = #alarms{alarmed_nodes = AN,
alertees = Alertees}) ->
AN1 = UpdateFun(Node, Source, AN),
BeforeSz = count_dict_values(Source, AN),
AfterSz = count_dict_values(Source, AN1),
%% If we have changed our alarm state, inform the remotes.
IsLocal = Node =:= node(),
if IsLocal andalso BeforeSz < AfterSz ->
ok = alert_remote(true, Alertees, Source);
IsLocal andalso BeforeSz > AfterSz ->
ok = alert_remote(false, Alertees, Source);
true ->
ok
end,
%% If the overall alarm state has changed, inform the locals.
case {dict:size(AN), dict:size(AN1)} of
{0, 1} -> ok = alert_local(true, Alertees, Source);
{1, 0} -> ok = alert_local(false, Alertees, Source);
{_, _} -> ok
end,
State#alarms{alarmed_nodes = AN1}.
alert_local(Alert, Alertees, Source) ->
alert(Alertees, Source, Alert, fun erlang:'=:='/2).
alert_remote(Alert, Alertees, Source) ->
alert(Alertees, Source, Alert, fun erlang:'=/='/2).
alert(Alertees, Source, Alert, NodeComparator) ->
Node = node(),
dict:fold(fun (Pid, {M, F, A}, ok) ->
case NodeComparator(Node, node(Pid)) of
true -> apply(M, F, A ++ [Pid, Source, Alert]);
false -> ok
end
end, ok, Alertees).
internal_register(Pid, {M, F, A} = HighMemMFA,
State = #alarms{alertees = Alertees}) ->
_MRef = erlang:monitor(process, Pid),
case dict:find(node(), State#alarms.alarmed_nodes) of
{ok, Sources} -> [apply(M, F, A ++ [Pid, R, true]) || R <- Sources];
error -> ok
end,
NewAlertees = dict:store(Pid, HighMemMFA, Alertees),
State#alarms{alertees = NewAlertees}.
handle_set_alarm({{resource_limit, Source, Node}, []}, State) ->
rabbit_log:warning("~s resource limit alarm set on node ~p~n",
[Source, Node]),
{ok, maybe_alert(fun dict:append/3, Node, Source, State)};
handle_set_alarm({file_descriptor_limit, []}, State) ->
rabbit_log:warning("file descriptor limit alarm set~n"),
{ok, State};
handle_set_alarm(Alarm, State) ->
rabbit_log:warning("alarm '~p' set~n", [Alarm]),
{ok, State}.
handle_clear_alarm({resource_limit, Source, Node}, State) ->
rabbit_log:warning("~s resource limit alarm cleared on node ~p~n",
[Source, Node]),
{ok, maybe_alert(fun dict_unappend/3, Node, Source, State)};
handle_clear_alarm(file_descriptor_limit, State) ->
rabbit_log:warning("file descriptor limit alarm cleared~n"),
{ok, State};
handle_clear_alarm(Alarm, State) ->
rabbit_log:warning("alarm '~p' cleared~n", [Alarm]),
{ok, State}.
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