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/**
* Copyright (C) 2017 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 "mongo/db/logical_time.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
class ServiceContext;
class OperationContext;
/**
* LogicalClock maintain the clusterTime for a clusterNode. Every cluster node in a replica set has
* an instance of the LogicalClock installed as a ServiceContext decoration.
*/
class LogicalClock {
public:
// Decorate ServiceContext with LogicalClock instance.
static LogicalClock* get(ServiceContext* service);
static LogicalClock* get(OperationContext* ctx);
static void set(ServiceContext* service, std::unique_ptr<LogicalClock> logicalClock);
static const uint32_t kMaxSignedInt = ((1U << 31) - 1);
static constexpr Seconds kMaxAcceptableLogicalClockDriftSecs =
Seconds(365 * 24 * 60 * 60); // 1 year
/**
* Creates an instance of LogicalClock.
*/
LogicalClock(ServiceContext*);
/**
* The method sets current time to newTime if the newTime > current time and it passes the rate
* check.
*
* Returns an error if the newTime does not pass the rate check.
*/
Status advanceClusterTime(const LogicalTime newTime);
/**
* Returns the current clusterTime.
*/
LogicalTime getClusterTime();
/**
* Returns the next clusterTime value and provides a guarantee that any future call to
* reserveTicks() will return a value at least 'nTicks' ticks in the future from the current
* clusterTime.
*/
LogicalTime reserveTicks(uint64_t nTicks);
/**
* Resets current time to newTime. Should only be used for initializing this clock from an
* oplog timestamp.
*/
void setClusterTimeFromTrustedSource(LogicalTime newTime);
private:
/**
* Rate limiter for advancing cluster time. Rejects newTime if its seconds value is more than
* kMaxAcceptableLogicalClockDriftSecs seconds ahead of this node's wall clock.
*/
Status _passesRateLimiter_inlock(LogicalTime newTime);
ServiceContext* const _service;
// The mutex protects _clusterTime.
stdx::mutex _mutex;
LogicalTime _clusterTime;
};
} // namespace mongo
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