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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 <memory>
#include <ostream>
#include <string>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/status.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
namespace logger {
/**
* A synchronized file output stream writer, with support for file rotation.
*
* To enforce proper locking, instances of RotatableFileWriter may only be manipulated by
* instantiating a RotatableFileWriter::Use guard object, which exposes the relevant
* manipulation methods for the stream. For any instance of RotatableFileWriter, at most one
* fully constructed instance of RotatableFileWriter::Use exists at a time, providing mutual
* exclusion.
*
* Behavior is undefined if two instances of RotatableFileWriter should simultaneously have the
* same value for their fileName.
*/
class RotatableFileWriter {
MONGO_DISALLOW_COPYING(RotatableFileWriter);
public:
/**
* Guard class representing synchronous use of an instance of RotatableFileWriter.
*/
class Use {
MONGO_DISALLOW_COPYING(Use);
public:
/**
* Constructs a Use object for "writer", and lock "writer".
*/
explicit Use(RotatableFileWriter* writer);
/**
* Sets the name of the target file to which stream() writes to "name".
*
* May be called repeatedly.
*
* If this method does not return Status::OK(), it is not safe to call rotate() or
* stream().
*
* Set "append" to true to open "name" in append mode. Otherwise, it is truncated.
*/
Status setFileName(const std::string& name, bool append);
/**
* Rotates the currently opened file into "renameTarget", and open a new file
* with the name previously set via setFileName().
*
* renameFiles - true we rename the log file, false we expect it was renamed externally
*
* Returns Status::OK() on success. If the rename fails, returns
* ErrorCodes::FileRenameFailed, and the stream continues to write to the unrotated
* file. If the rename succeeds but the subsequent file open fails, returns
* ErrorCodes::FileNotOpen, and the stream continues to target the original file, though
* under its new name.
*/
Status rotate(bool renameFile, const std::string& renameTarget);
/**
* Returns the status of the stream.
*
* One of Status::OK(), ErrorCodes::FileNotOpen and ErrorCodes::FileStreamFailed.
*/
Status status();
/**
* Returns a reference to the std::ostream() through which users may write to the file.
*/
std::ostream& stream() {
return *_writer->_stream;
}
private:
/**
* Helper that opens the file named by setFileName(), in the mode specified by "append".
*
* Returns Status::OK() on success and ErrorCodes::FileNotOpen on failure.
*/
Status _openFileStream(bool append);
RotatableFileWriter* _writer;
stdx::unique_lock<stdx::mutex> _lock;
};
/**
* Constructs an instance of RotatableFileWriter.
*/
RotatableFileWriter();
private:
friend class RotatableFileWriter::Use;
stdx::mutex _mutex;
std::string _fileName;
std::unique_ptr<std::ostream> _stream;
};
} // namespace logger
} // namespace mongo
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