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Modules shared by rabbitmq-server and rabbitmq-erlang-client
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Files
src/rabbit_event.erl
%% 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 https://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 GoPivotal, Inc.
%% Copyright (c) 2007-2017 Pivotal Software, Inc. All rights reserved.
%%
-module(rabbit_event).
-include("rabbit.hrl").
-export([start_link/0]).
-export([init_stats_timer/2, init_disabled_stats_timer/2,
ensure_stats_timer/3, stop_stats_timer/2, reset_stats_timer/2]).
-export([stats_level/2, if_enabled/3]).
-export([notify/2, notify/3, notify_if/3]).
-export([sync_notify/2, sync_notify/3]).
-ignore_xref([{gen_event, start_link, 2}]).
-dialyzer([{no_missing_calls, start_link/0}]).
%%----------------------------------------------------------------------------
-record(state, {level, interval, timer}).
%%----------------------------------------------------------------------------
-export_type([event_type/0, event_props/0, event_timestamp/0, event/0]).
-type event_type() :: atom().
-type event_props() :: term().
-type event_timestamp() :: non_neg_integer().
-type event() :: #event { type :: event_type(),
props :: event_props(),
reference :: 'none' | reference(),
timestamp :: event_timestamp() }.
-type level() :: 'none' | 'coarse' | 'fine'.
-type timer_fun() :: fun (() -> 'ok').
-type container() :: tuple().
-type pos() :: non_neg_integer().
-spec start_link() -> rabbit_types:ok_pid_or_error().
-spec init_stats_timer(container(), pos()) -> container().
-spec init_disabled_stats_timer(container(), pos()) -> container().
-spec ensure_stats_timer(container(), pos(), term()) -> container().
-spec stop_stats_timer(container(), pos()) -> container().
-spec reset_stats_timer(container(), pos()) -> container().
-spec stats_level(container(), pos()) -> level().
-spec if_enabled(container(), pos(), timer_fun()) -> 'ok'.
-spec notify(event_type(), event_props()) -> 'ok'.
-spec notify(event_type(), event_props(), reference() | 'none') -> 'ok'.
-spec notify_if(boolean(), event_type(), event_props()) -> 'ok'.
-spec sync_notify(event_type(), event_props()) -> 'ok'.
-spec sync_notify(event_type(), event_props(), reference() | 'none') -> 'ok'.
%%----------------------------------------------------------------------------
start_link() ->
%% gen_event:start_link/2 is not available before OTP 20
%% RabbitMQ 3.7 supports OTP >= 19.3
case erlang:function_exported(gen_event, start_link, 2) of
true ->
gen_event:start_link(
{local, ?MODULE},
[{spawn_opt, [{fullsweep_after, 0}]}]
);
false ->
gen_event:start_link({local, ?MODULE})
end.
%% The idea is, for each stat-emitting object:
%%
%% On startup:
%% init_stats_timer(State)
%% notify(created event)
%% if_enabled(internal_emit_stats) - so we immediately send something
%%
%% On wakeup:
%% ensure_stats_timer(State, emit_stats)
%% (Note we can't emit stats immediately, the timer may have fired 1ms ago.)
%%
%% emit_stats:
%% if_enabled(internal_emit_stats)
%% reset_stats_timer(State) - just bookkeeping
%%
%% Pre-hibernation:
%% if_enabled(internal_emit_stats)
%% stop_stats_timer(State)
%%
%% internal_emit_stats:
%% notify(stats)
init_stats_timer(C, P) ->
%% If the rabbit app is not loaded - use default none:5000
StatsLevel = application:get_env(rabbit, collect_statistics, none),
Interval = application:get_env(rabbit, collect_statistics_interval, 5000),
setelement(P, C, #state{level = StatsLevel, interval = Interval,
timer = undefined}).
init_disabled_stats_timer(C, P) ->
setelement(P, C, #state{level = none, interval = 0, timer = undefined}).
ensure_stats_timer(C, P, Msg) ->
case element(P, C) of
#state{level = Level, interval = Interval, timer = undefined} = State
when Level =/= none ->
TRef = erlang:send_after(Interval, self(), Msg),
setelement(P, C, State#state{timer = TRef});
#state{} ->
C
end.
stop_stats_timer(C, P) ->
case element(P, C) of
#state{timer = TRef} = State when TRef =/= undefined ->
case erlang:cancel_timer(TRef) of
false -> C;
_ -> setelement(P, C, State#state{timer = undefined})
end;
#state{} ->
C
end.
reset_stats_timer(C, P) ->
case element(P, C) of
#state{timer = TRef} = State when TRef =/= undefined ->
setelement(P, C, State#state{timer = undefined});
#state{} ->
C
end.
stats_level(C, P) ->
#state{level = Level} = element(P, C),
Level.
if_enabled(C, P, Fun) ->
case element(P, C) of
#state{level = none} -> ok;
#state{} -> Fun(), ok
end.
notify_if(true, Type, Props) -> notify(Type, Props);
notify_if(false, _Type, _Props) -> ok.
notify(Type, Props) -> notify(Type, Props, none).
notify(Type, Props, Ref) ->
%% Using {Name, node()} here to not fail if the event handler is not started
gen_event:notify({?MODULE, node()}, event_cons(Type, Props, Ref)).
sync_notify(Type, Props) -> sync_notify(Type, Props, none).
sync_notify(Type, Props, Ref) ->
gen_event:sync_notify(?MODULE, event_cons(Type, Props, Ref)).
event_cons(Type, Props, Ref) ->
#event{type = Type,
props = Props,
reference = Ref,
timestamp = os:system_time(milli_seconds)}.