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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/util/alarm_runner_background_thread.h"
namespace mongo {
void AlarmRunnerBackgroundThread::start() {
stdx::lock_guard<Latch> lk(_mutex);
_running = true;
_thread = stdx::thread(&AlarmRunnerBackgroundThread::_threadRoutine, this);
}
void AlarmRunnerBackgroundThread::shutdown() {
stdx::unique_lock<Latch> lk(_mutex);
_running = false;
lk.unlock();
_condVar.notify_one();
_thread.join();
for (const auto& scheduler : _schedulers) {
scheduler->clearAllAlarmsAndShutdown();
}
}
std::vector<AlarmRunnerBackgroundThread::AlarmSchedulerHandle>
AlarmRunnerBackgroundThread::_initializeSchedulers(std::vector<AlarmSchedulerHandle> schedulers) {
invariant(!schedulers.empty());
const auto registerHook = [this](Date_t next, const std::shared_ptr<AlarmScheduler>& which) {
stdx::unique_lock<Latch> lk(_mutex);
if (next >= _nextAlarm) {
return;
}
_nextAlarm = next;
_condVar.notify_one();
};
const auto clockSource = schedulers.front()->clockSource();
for (auto& scheduler : schedulers) {
scheduler->setAlarmRegisterHook(registerHook);
auto nextAlarm = scheduler->nextAlarm();
if (nextAlarm < _nextAlarm) {
_nextAlarm = nextAlarm;
}
// The thread routine uses the clock source of the first registered scheduler to wait
// on its condvar, so all registered schedulers must use the same clock source.
fassert(51046, scheduler->clockSource() == clockSource);
}
return schedulers;
}
void AlarmRunnerBackgroundThread::_threadRoutine() {
stdx::unique_lock<Latch> lk(_mutex);
while (_running) {
const auto clockSource = _schedulers.front()->clockSource();
const auto now = clockSource->now();
// Schedulers may try to alter our _nextAlarm/_newAlarm state as they process expired
// alarms that then reschedule themselves, so to eliminate any lock contention, just
// unlock the mutex while we process expired alarms.
lk.unlock();
for (const auto& scheduler : _schedulers) {
if (scheduler->nextAlarm() > now) {
continue;
}
scheduler->processExpiredAlarms();
}
// Lock the mutex while the sleep duration is computed. This will block schedulers from
// scheduling new alarms.
lk.lock();
auto sleepUntil = Date_t::max();
for (const auto& scheduler : _schedulers) {
sleepUntil = std::min(sleepUntil, scheduler->nextAlarm());
}
// Update _nextAlarm so that any schedulers that have pending new alarms see the actual
// time we're about to sleep for, and set _newAlarm to false before going to sleep.
_nextAlarm = sleepUntil;
clockSource->waitForConditionUntil(_condVar, lk, _nextAlarm, [&] {
return (_nextAlarm != sleepUntil || _running == false);
});
}
}
} // namespace mongo
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