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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.
*/
#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 {
if (left->getDeadline() > right->getDeadline()) {
return true;
}
if (left->getDeadline() == right->getDeadline()) {
return left->getId() > right->getId();
}
return false;
}
};
/**
* Priority Queue with ability to remove items by filter.
*/
class FreeMonPriorityQueue {
public:
bool empty() const {
return _vector.empty();
}
/**
* Return the message at the top of the priority queue.
*/
std::shared_ptr<FreeMonMessage> top() const;
/**
* Pop the message at the top of the priority queue.
*/
void pop();
/**
* Push a message into the priority queue.
*/
void push(std::shared_ptr<FreeMonMessage> item);
/**
* Erase messages of a given type from the queue.
*/
void eraseByType(FreeMonMessageType type);
private:
// Using shared_ptr because std::pop_heap does not support move-only types
std::vector<std::shared_ptr<FreeMonMessage>> _vector;
FreeMonMessageGreater _comp;
};
/**
* 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
FreeMonPriorityQueue _queue;
// Use manual crank to process messages in-order instead of based on deadlines.
bool _useCrank{false};
// Stamp each message with a unique counter. This ensures that if two messages are queued with
// the same deadline, FIFO is achieved.
uint64_t _counter{0};
// 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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