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/**
* Copyright (C) 2019-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 <map>
#include <memory>
#include <vector>
#include "mongo/db/repl/optime.h"
#include "mongo/db/service_context.h"
#include "mongo/executor/task_executor.h"
#include "mongo/stdx/mutex.h"
#include "mongo/stdx/thread.h"
#include "mongo/util/future.h"
namespace mongo {
/**
* Provides a facility for asynchronously waiting a local opTime to be majority committed.
*/
class WaitForMajorityService {
public:
~WaitForMajorityService();
static WaitForMajorityService& get(ServiceContext* service);
/**
* Sets up the background thread responsible for waiting for opTimes to be majority committed.
*/
void setUp(ServiceContext* service);
/**
* Blocking method, which shuts down and joins the background thread.
*/
void shutDown();
/**
* Enqueue a request to wait for the given opTime to be majority committed.
*/
SharedSemiFuture<void> waitUntilMajority(const repl::OpTime& opTime);
private:
using OpTimeWaitingMap = std::map<repl::OpTime, SharedPromise<void>>;
/**
* Periodically checks the list of opTimes to wait for majority committed.
*/
void _periodicallyWaitForMajority(ServiceContext* service);
stdx::mutex _mutex;
// Contains an ordered list of opTimes to wait to be majority comitted.
OpTimeWaitingMap _queuedOpTimes;
// Contains the last opTime that the background thread was able to successfully wait to be
// majority comitted.
repl::OpTime _lastOpTimeWaited;
// The background thread.
stdx::thread _thread;
// Use for signalling new opTime requests being queued.
stdx::condition_variable _hasNewOpTimeCV;
// If set, contains a reference to the opCtx being used by the background thread.
// Only valid when _thread.joinable() and not nullptr.
OperationContext* _opCtx{nullptr};
// Flag is set to true after shutDown() is called.
bool _inShutDown{false};
};
} // namespace mongo
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