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/**
* Copyright (C) 2018 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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.
*/
#pragma once
#include <boost/optional.hpp>
#include <memory>
#include <mutex>
#include <queue>
#include <vector>
#include "mongo/db/free_mon/free_mon_message.h"
#include "mongo/util/clock_source.h"
#include "mongo/util/time_support.h"
namespace mongo {
/**
* Comparator for FreeMonMessage that will sort smallest deadlines at the beginning of a priority
* queue. The std::priority_queue is a max-heap.
*/
struct FreeMonMessageGreater {
bool operator()(const std::shared_ptr<FreeMonMessage>& left,
const std::shared_ptr<FreeMonMessage>& right) const {
return (left->getDeadline() > right->getDeadline());
}
};
/**
* A multi-producer, single-consumer queue with deadlines.
*
* The smallest deadline sorts first. Messages with deadlines can be use as a timer mechanism.
*/
class FreeMonMessageQueue {
public:
FreeMonMessageQueue(bool useCrankForTest = false) : _useCrank(useCrankForTest) {}
/**
* Enqueue a message and wake consumer if needed.
*
* Messages are dropped if the queue has been stopped.
*/
void enqueue(std::shared_ptr<FreeMonMessage> msg);
/**
* Deque a message from the queue.
*
* Waits for a message to arrive. Returns boost::none if the queue has been stopped.
*/
boost::optional<std::shared_ptr<FreeMonMessage>> dequeue(ClockSource* clockSource);
/**
* Stop the queue.
*/
void stop();
/**
* Turn the crank of the message queue by ignoring deadlines for N messages.
*/
void turnCrankForTest(size_t countMessagesToIgnore);
private:
// Condition variable to signal consumer
stdx::condition_variable _condvar;
// Lock for condition variable and to protect state
stdx::mutex _mutex;
// Indicates whether queue has been stopped.
bool _stop{false};
// Priority queue of messages with shortest deadline first
// Using shared_ptr because priority_queue does not support move-only types
std::priority_queue<std::shared_ptr<FreeMonMessage>,
std::vector<std::shared_ptr<FreeMonMessage>>,
FreeMonMessageGreater>
_queue;
// Use manual crank to process messages in-order instead of based on deadlines.
bool _useCrank{false};
// Number of messages to ignore
size_t _countMessagesToIgnore{0};
// Number of messages that have been ignored
size_t _countMessagesIgnored{0};
// Waitable result for testing
std::unique_ptr<WaitableResult> _waitable;
};
} // namespace mongo
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