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% Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
% License for the specific language governing permissions and limitations under
% the License.
-module(couch_expiring_cache_server).
-behaviour(gen_server).
-callback start_link() -> {ok, pid()} | ignore | {error, term()}.
-export([
start_link/2
]).
-export([
init/1,
terminate/2,
handle_call/3,
handle_cast/2,
handle_info/2,
code_change/3
]).
-define(DEFAULT_BATCH_SIZE, 1000).
-define(DEFAULT_PERIOD_MSEC, 5000).
-define(DEFAULT_MAX_JITTER_MSEC, 1000).
-include_lib("couch_expiring_cache/include/couch_expiring_cache.hrl").
start_link(Name, Opts) when is_atom(Name) ->
gen_server:start_link({local, Name}, ?MODULE, Opts#{name => Name}, []).
init(Opts) ->
DefaultCacheName = atom_to_binary(maps:get(name, Opts), utf8),
Period = maps:get(period, Opts, ?DEFAULT_PERIOD_MSEC),
MaxJitter = maps:get(max_jitter, Opts, ?DEFAULT_MAX_JITTER_MSEC),
{ok, #{
cache_name => maps:get(cache_name, Opts, DefaultCacheName),
batch_size => maps:get(batch_size, Opts, ?DEFAULT_BATCH_SIZE),
period => Period,
max_jitter => MaxJitter,
timer_ref => schedule_remove_expired(Period, MaxJitter),
oldest_ts => 0,
elapsed => 0,
largest_elapsed => 0,
lag => 0}}.
terminate(_, _) ->
ok.
handle_call(Msg, _From, St) ->
{stop, {bad_call, Msg}, {bad_call, Msg}, St}.
handle_cast(Msg, St) ->
{stop, {bad_cast, Msg}, St}.
handle_info(remove_expired, St) ->
#{
cache_name := Name,
batch_size := BatchSize,
period := Period,
max_jitter := MaxJitter,
oldest_ts := OldestTS0,
largest_elapsed := LargestElapsed
} = St,
NowTS = erlang:system_time(?TIME_UNIT),
OldestTS = max(OldestTS0,
couch_expiring_cache_fdb:clear_range_to(Name, NowTS, BatchSize)),
Elapsed = erlang:system_time(?TIME_UNIT) - NowTS,
{noreply, St#{
timer_ref := schedule_remove_expired(Period, MaxJitter),
oldest_ts := OldestTS,
elapsed := Elapsed,
largest_elapsed := max(Elapsed, LargestElapsed),
lag := NowTS - OldestTS}};
handle_info({Ref, ready}, St) when is_reference(Ref) ->
% Prevent crashing server and application
LogMsg = "~p : spurious erlfdb future ready message ~p",
couch_log:error(LogMsg, [?MODULE, Ref]),
{noreply, St};
handle_info(Msg, St) ->
{stop, {bad_info, Msg}, St}.
code_change(_OldVsn, St, _Extra) ->
{ok, St}.
%% Private
schedule_remove_expired(Timeout, MaxJitter) ->
Jitter = max(Timeout div 2, MaxJitter),
Wait = Timeout + rand:uniform(max(1, Jitter)),
erlang:send_after(Wait, self(), remove_expired).
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