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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 <string>
#include "mongo/base/status.h"
#include "mongo/db/service_context.h"
namespace mongo {
constexpr StringData kLockFileBasename = "mongod.lock"_sd;
class StorageEngineLockFile {
StorageEngineLockFile(const StorageEngineLockFile&) = delete;
StorageEngineLockFile& operator=(const StorageEngineLockFile&) = delete;
public:
static boost::optional<StorageEngineLockFile>& get(ServiceContext* service);
/**
* Checks existing lock file, if present, to see if it contains data from a previous
* unclean shutdown. A clean shutdown should have produced a zero length lock file.
* Uses open() to read existing lock file or create new file.
* Uses boost::filesystem to check lock file so may throw boost::exception.
*/
StorageEngineLockFile(const std::string& dbpath, StringData fileName = kLockFileBasename);
virtual ~StorageEngineLockFile();
/**
* Returns the path to the lock file.
*/
std::string getFilespec() const;
/**
* Returns true if lock file was not zeroed out due to previous unclean shutdown.
* This state is evaluated at object initialization to allow storage engine
* to make decisions on recovery based on this information after open() has been called.
*/
bool createdByUncleanShutdown() const;
/**
* Opens and locks 'mongod.lock' in 'dbpath' directory.
*/
Status open();
/**
* Closes lock file handles.
*/
void close();
/**
* Writes current process ID to file.
* Fails if lock file has not been opened.
*/
Status writePid();
/**
* Writes the string to file.
* Fails if lock file has not been opened.
*/
Status writeString(StringData str);
/**
* Truncates file contents and releases file locks.
*/
void clearPidAndUnlock();
private:
std::string _getNonExistentPathMessage() const;
std::string _dbpath;
std::string _filespec;
bool _uncleanShutdown;
class LockFileHandle;
std::unique_ptr<LockFileHandle> _lockFileHandle;
};
} // namespace mongo
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