| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you 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. |
| |
| #include "kudu/rpc/periodic.h" |
| |
| #include <algorithm> |
| #include <memory> |
| #include <mutex> |
| |
| #include <boost/function.hpp> |
| #include <glog/logging.h> |
| |
| #include "kudu/rpc/messenger.h" |
| #include "kudu/util/monotime.h" |
| #include "kudu/util/random.h" |
| #include "kudu/util/random_util.h" |
| #include "kudu/util/status.h" |
| |
| using std::shared_ptr; |
| using std::weak_ptr; |
| |
| namespace kudu { |
| namespace rpc { |
| |
| PeriodicTimer::Options::Options() |
| : jitter_pct(0.25), |
| one_shot(false) { |
| } |
| |
| shared_ptr<PeriodicTimer> PeriodicTimer::Create( |
| shared_ptr<Messenger> messenger, |
| RunTaskFunctor functor, |
| MonoDelta period, |
| Options options) { |
| return PeriodicTimer::make_shared( |
| std::move(messenger), std::move(functor), period, options); |
| } |
| |
| PeriodicTimer::PeriodicTimer( |
| shared_ptr<Messenger> messenger, |
| RunTaskFunctor functor, |
| MonoDelta period, |
| Options options) |
| : messenger_(std::move(messenger)), |
| functor_(std::move(functor)), |
| period_(period), |
| options_(options), |
| rng_(GetRandomSeed32()), |
| current_callback_generation_(0), |
| num_callbacks_for_tests_(0), |
| started_(false) { |
| DCHECK_GE(options_.jitter_pct, 0); |
| DCHECK_LE(options_.jitter_pct, 1); |
| } |
| |
| PeriodicTimer::~PeriodicTimer() { |
| Stop(); |
| } |
| |
| void PeriodicTimer::Start(boost::optional<MonoDelta> next_task_delta) { |
| std::unique_lock<simple_spinlock> l(lock_); |
| if (!started_) { |
| started_ = true; |
| SnoozeUnlocked(std::move(next_task_delta)); |
| int new_callback_generation = ++current_callback_generation_; |
| |
| // Invoke Callback() with the lock released. |
| l.unlock(); |
| Callback(new_callback_generation); |
| } |
| } |
| |
| void PeriodicTimer::Stop() { |
| std::lock_guard<simple_spinlock> l(lock_); |
| StopUnlocked(); |
| } |
| |
| void PeriodicTimer::StopUnlocked() { |
| DCHECK(lock_.is_locked()); |
| started_ = false; |
| } |
| |
| void PeriodicTimer::Snooze(boost::optional<MonoDelta> next_task_delta) { |
| std::lock_guard<simple_spinlock> l(lock_); |
| SnoozeUnlocked(std::move(next_task_delta)); |
| } |
| |
| void PeriodicTimer::SnoozeUnlocked(boost::optional<MonoDelta> next_task_delta) { |
| DCHECK(lock_.is_locked()); |
| if (!started_) { |
| return; |
| } |
| |
| if (!next_task_delta) { |
| // Given jitter percentage J and period P, this yields a delay somewhere |
| // between (1-J)*P and (1+J)*P. |
| next_task_delta = MonoDelta::FromMilliseconds( |
| GetMinimumPeriod().ToMilliseconds() + |
| rng_.NextDoubleFraction() * |
| options_.jitter_pct * |
| (2 * period_.ToMilliseconds())); |
| } |
| next_task_time_ = MonoTime::Now() + *next_task_delta; |
| } |
| |
| bool PeriodicTimer::started() const { |
| std::lock_guard<simple_spinlock> l(lock_); |
| return started_; |
| } |
| |
| MonoDelta PeriodicTimer::GetMinimumPeriod() { |
| // Given jitter percentage J and period P, this returns (1-J)*P, which is |
| // the lowest possible jittered value. |
| return MonoDelta::FromMilliseconds((1.0 - options_.jitter_pct) * |
| period_.ToMilliseconds()); |
| } |
| |
| int64_t PeriodicTimer::NumCallbacksForTests() const { |
| std::lock_guard<simple_spinlock> l(lock_); |
| return num_callbacks_for_tests_; |
| } |
| |
| void PeriodicTimer::Callback(int64_t my_callback_generation) { |
| // To simplify the implementation, a timer may have only one outstanding |
| // callback scheduled at a time. This means that once the callback is |
| // scheduled, the timer's task cannot run any earlier than whenever the |
| // callback runs. Thus, the delay used when scheduling the callback dictates |
| // the lowest possible value of 'next_task_delta' that Snooze() can honor. |
| // |
| // If the callback's delay is very low, Snooze() can honor a low |
| // 'next_task_delta', but the callback will run often and burn more CPU |
| // cycles. If the delay is very high, the timer will be more efficient but |
| // the granularity for 'next_task_delta' will rise accordingly. |
| // |
| // As a "happy medium" we use GetMinimumPeriod() as the delay. This ensures |
| // that a no-arg Snooze() on a jittered timer will always be honored, and as |
| // long as the caller passes a value of at least GetMinimumPeriod() to |
| // Snooze(), that too will be honored. |
| MonoDelta delay = GetMinimumPeriod(); |
| bool run_task = false; |
| { |
| std::lock_guard<simple_spinlock> l(lock_); |
| num_callbacks_for_tests_++; |
| |
| // If the timer was stopped, exit. |
| if (!started_) { |
| return; |
| } |
| |
| // If there's a new callback loop in town, exit. |
| // |
| // We could check again just before calling Messenger::ScheduleOnReactor() |
| // (in case someone else restarted the timer while the functor ran, or in |
| // case the functor itself restarted the timer), but there's no real reason |
| // to do so: the very next iteration of this callback loop will wind up here |
| // and exit. |
| if (current_callback_generation_ > my_callback_generation) { |
| return; |
| } |
| |
| MonoTime now = MonoTime::Now(); |
| if (now < next_task_time_) { |
| // It's not yet time to run the task. Reduce the scheduled delay if |
| // enough time has elapsed, but don't increase it. |
| delay = std::min(delay, next_task_time_ - now); |
| } else { |
| // It's time to run the task. Although the next task time is reset now, |
| // it may be reset again by virtue of running the task itself. |
| run_task = true; |
| |
| if (options_.one_shot) { |
| // Stop the timer first, in case the task wants to restart it. |
| StopUnlocked(); |
| } |
| } |
| } |
| |
| if (run_task) { |
| functor_(); |
| |
| if (options_.one_shot) { |
| // The task was run; exit the loop. Even if the task restarted the timer, |
| // that will have started a new callback loop, so exiting here is always |
| // the correct thing to do. |
| return; |
| } |
| Snooze(); |
| } |
| |
| // Capture a weak_ptr reference into the submitted functor so that we can |
| // safely handle the functor outliving its timer. |
| weak_ptr<PeriodicTimer> w = shared_from_this(); |
| messenger_->ScheduleOnReactor([w, my_callback_generation](const Status& s) { |
| if (!s.ok()) { |
| // The reactor was shut down. |
| return; |
| } |
| if (auto timer = w.lock()) { |
| timer->Callback(my_callback_generation); |
| } |
| }, delay); |
| } |
| |
| } // namespace rpc |
| } // namespace kudu |