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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 Developers of the Original Code are LShift Ltd,
%% Cohesive Financial Technologies LLC, and Rabbit Technologies Ltd.
%%
%% Portions created before 22-Nov-2008 00:00:00 GMT by LShift Ltd,
%% Cohesive Financial Technologies LLC, or Rabbit Technologies Ltd
%% are Copyright (C) 2007-2008 LShift Ltd, Cohesive Financial
%% Technologies LLC, and Rabbit Technologies Ltd.
%%
%% Portions created by LShift Ltd are Copyright (C) 2007-2009 LShift
%% Ltd. Portions created by Cohesive Financial Technologies LLC are
%% Copyright (C) 2007-2009 Cohesive Financial Technologies
%% LLC. Portions created by Rabbit Technologies Ltd are Copyright
%% (C) 2007-2009 Rabbit Technologies Ltd.
%%
%% All Rights Reserved.
%%
%% Contributor(s): ______________________________________.
%%
-module(rabbit_alarm).
-behaviour(gen_event).
-export([start/1, stop/0, register/2]).
-export([init/1, handle_call/2, handle_event/2, handle_info/2,
terminate/2, code_change/3]).
-define(MEMSUP_CHECK_INTERVAL, 1000).
%% OSes on which we know memory alarms to be trustworthy
-define(SUPPORTED_OS, [{unix, linux}, {unix, darwin}]).
-record(alarms, {alertees, system_memory_high_watermark = false}).
%%----------------------------------------------------------------------------
-ifdef(use_specs).
-type(mfa_tuple() :: {atom(), atom(), list()}).
-spec(start/1 :: (bool() | 'auto') -> 'ok').
-spec(stop/0 :: () -> 'ok').
-spec(register/2 :: (pid(), mfa_tuple()) -> 'ok').
-endif.
%%----------------------------------------------------------------------------
start(MemoryAlarms) ->
EnableAlarms = case MemoryAlarms of
true -> true;
false -> false;
auto -> lists:member(os:type(), ?SUPPORTED_OS)
end,
ok = alarm_handler:add_alarm_handler(?MODULE, [EnableAlarms]),
case whereis(memsup) of
undefined -> if EnableAlarms -> ok = start_memsup(),
ok = adjust_memsup_interval();
true -> ok
end;
_ -> ok = adjust_memsup_interval()
end.
stop() ->
ok = alarm_handler:delete_alarm_handler(?MODULE).
register(Pid, HighMemMFA) ->
ok = gen_event:call(alarm_handler, ?MODULE,
{register, Pid, HighMemMFA},
infinity).
%%----------------------------------------------------------------------------
init([MemoryAlarms]) ->
{ok, #alarms{alertees = case MemoryAlarms of
true -> dict:new();
false -> undefined
end}}.
handle_call({register, _Pid, _HighMemMFA},
State = #alarms{alertees = undefined}) ->
{ok, ok, State};
handle_call({register, Pid, HighMemMFA},
State = #alarms{alertees = Alertess}) ->
_MRef = erlang:monitor(process, Pid),
case State#alarms.system_memory_high_watermark of
true -> {M, F, A} = HighMemMFA,
ok = erlang:apply(M, F, A ++ [Pid, true]);
false -> ok
end,
NewAlertees = dict:store(Pid, HighMemMFA, Alertess),
{ok, ok, State#alarms{alertees = NewAlertees}};
handle_call(_Request, State) ->
{ok, not_understood, State}.
handle_event({set_alarm, {system_memory_high_watermark, []}}, State) ->
ok = alert(true, State#alarms.alertees),
{ok, State#alarms{system_memory_high_watermark = true}};
handle_event({clear_alarm, system_memory_high_watermark}, State) ->
ok = alert(false, State#alarms.alertees),
{ok, State#alarms{system_memory_high_watermark = false}};
handle_event(_Event, State) ->
{ok, State}.
handle_info({'DOWN', _MRef, process, _Pid, _Reason},
State = #alarms{alertees = undefined}) ->
{ok, State};
handle_info({'DOWN', _MRef, process, Pid, _Reason},
State = #alarms{alertees = Alertess}) ->
{ok, State#alarms{alertees = dict:erase(Pid, Alertess)}};
handle_info(_Info, State) ->
{ok, State}.
terminate(_Arg, _State) ->
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
%%----------------------------------------------------------------------------
start_memsup() ->
{Mod, Args} =
case os:type() of
%% memsup doesn't take account of buffers or cache when
%% considering "free" memory - therefore on Linux we can
%% get memory alarms very easily without any pressure
%% existing on memory at all. Therefore we need to use
%% our own simple memory monitor.
%%
{unix, linux} -> {rabbit_memsup, [rabbit_memsup_linux]};
{unix, darwin} -> {rabbit_memsup, [rabbit_memsup_darwin]};
%% Start memsup programmatically rather than via the
%% rabbitmq-server script. This is not quite the right
%% thing to do as os_mon checks to see if memsup is
%% available before starting it, but as memsup is
%% available everywhere (even on VXWorks) it should be
%% ok.
%%
%% One benefit of the programmatic startup is that we
%% can add our alarm_handler before memsup is running,
%% thus ensuring that we notice memory alarms that go
%% off on startup.
%%
_ -> {memsup, []}
end,
%% This is based on os_mon:childspec(memsup, true)
{ok, _} = supervisor:start_child(
os_mon_sup,
{memsup, {Mod, start_link, Args},
permanent, 2000, worker, [Mod]}),
ok.
adjust_memsup_interval() ->
%% The default memsup check interval is 1 minute, which is way too
%% long - rabbit can gobble up all memory in a matter of seconds.
%% Unfortunately the memory_check_interval configuration parameter
%% and memsup:set_check_interval/1 function only provide a
%% granularity of minutes. So we have to peel off one layer of the
%% API to get to the underlying layer which operates at the
%% granularity of milliseconds.
%%
%% Note that the new setting will only take effect after the first
%% check has completed, i.e. after one minute. So if rabbit eats
%% all the memory within the first minute after startup then we
%% are out of luck.
ok = os_mon:call(memsup,
{set_check_interval, ?MEMSUP_CHECK_INTERVAL},
infinity).
alert(_Alert, undefined) ->
ok;
alert(Alert, Alertees) ->
dict:fold(fun (Pid, {M, F, A}, Acc) ->
ok = erlang:apply(M, F, A ++ [Pid, Alert]),
Acc
end, ok, Alertees).
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