1%% This Source Code Form is subject to the terms of the Mozilla Public
2%% License, v. 2.0. If a copy of the MPL was not distributed with this
3%% file, You can obtain one at https://mozilla.org/MPL/2.0/.
4%%
5%% Copyright (c) 2007-2021 VMware, Inc. or its affiliates.  All rights reserved.
6%%
7
8-module(background_gc).
9
10-behaviour(gen_server2).
11
12-export([start_link/0, run/0]).
13-export([gc/0]). %% For run_interval only
14
15-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
16         terminate/2, code_change/3]).
17
18-define(MAX_RATIO, 0.01).
19-define(MAX_INTERVAL, 240000).
20
21-record(state, {last_interval}).
22
23%%----------------------------------------------------------------------------
24
25-spec start_link() -> {'ok', pid()} | {'error', any()}.
26
27start_link() -> gen_server2:start_link({local, ?MODULE}, ?MODULE, [],
28                                       [{timeout, infinity}]).
29
30-spec run() -> 'ok'.
31
32run() -> gen_server2:cast(?MODULE, run).
33
34%%----------------------------------------------------------------------------
35
36init([]) ->
37    {ok, IdealInterval} = application:get_env(rabbit, background_gc_target_interval),
38    {ok, interval_gc(#state{last_interval = IdealInterval})}.
39
40handle_call(Msg, _From, State) ->
41    {stop, {unexpected_call, Msg}, {unexpected_call, Msg}, State}.
42
43handle_cast(run, State) -> gc(), {noreply, State};
44
45handle_cast(Msg, State) -> {stop, {unexpected_cast, Msg}, State}.
46
47handle_info(run, State) -> {noreply, interval_gc(State)};
48
49handle_info(Msg, State) -> {stop, {unexpected_info, Msg}, State}.
50
51code_change(_OldVsn, State, _Extra) -> {ok, State}.
52
53terminate(_Reason, State) -> State.
54
55%%----------------------------------------------------------------------------
56
57interval_gc(State = #state{last_interval = LastInterval}) ->
58    {ok, IdealInterval} = application:get_env(rabbit, background_gc_target_interval),
59    {ok, Interval} = rabbit_misc:interval_operation(
60                       {?MODULE, gc, []},
61                       ?MAX_RATIO, ?MAX_INTERVAL, IdealInterval, LastInterval),
62    erlang:send_after(Interval, self(), run),
63    State#state{last_interval = Interval}.
64
65-spec gc() -> 'ok'.
66
67gc() ->
68    Enabled = rabbit_misc:get_env(rabbit, background_gc_enabled, false),
69    case Enabled of
70        true ->
71            [garbage_collect(P) || P <- processes(),
72                                   {status, waiting} == process_info(P, status)],
73            %% since we will never be waiting...
74            garbage_collect();
75         false ->
76            ok
77    end,
78    ok.
79