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/*
* Copyright (C) 2015 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 <boost/optional.hpp>
#include "mongo/base/disallow_copying.h"
#include "mongo/client/read_preference.h"
#include "mongo/db/operation_context.h"
namespace mongo {
class BSONObj;
class BSONObjBuilder;
class Status;
template <typename T> class StatusWith;
namespace rpc {
/**
* This class comprises the request metadata fields that concern server selection, that is,
* the conditions on which servers can execute this operation.
*/
class ServerSelectionMetadata {
MONGO_DISALLOW_COPYING(ServerSelectionMetadata);
public:
static const OperationContext::Decoration<ServerSelectionMetadata> get;
// TODO: Remove when StatusWith supports default-constructible types (SERVER-18007).
ServerSelectionMetadata() = default;
#if defined(_MSC_VER) && _MSC_VER < 1900
ServerSelectionMetadata(ServerSelectionMetadata&&);
ServerSelectionMetadata& operator=(ServerSelectionMetadata&&);
#else
ServerSelectionMetadata(ServerSelectionMetadata&&) = default;
ServerSelectionMetadata& operator=(ServerSelectionMetadata&&) = default;
#endif
/**
* Loads ServerSelectionMetadata from a metadata object and stores it on this
* OperationContext.
*/
static StatusWith<ServerSelectionMetadata> readFromMetadata(const BSONObj& metadataObj);
/**
* Writes this operation's ServerSelectionMetadata to a metadata object.
*/
static Status writeToMetadata(const ServerSelectionMetadata& ss,
BSONObjBuilder* metadataBob);
/**
* Rewrites the ServerSelectionMetadata from the legacy OP_QUERY format to the metadata
* object format. In particular, if secondaryOk is set, this will set QueryOption_SlaveOk
* on the legacyQueryFlags. If a readPreference is set, the legacy command will be wrapped
* in a 'query' element and a top-level $readPreference field will be set on the command.
*/
static Status downconvert(const BSONObj& command,
const BSONObj& metadata,
BSONObjBuilder* legacyCommand,
int* legacyQueryFlags);
/**
* Rewrites the ServerSelectionMetadata from the legacy OP_QUERY format to the metadata
* object format.
*/
static Status upconvert(const BSONObj& legacyCommand,
const int legacyQueryFlags,
BSONObjBuilder* commandBob,
BSONObjBuilder* metadataBob);
/**
* Returns true if this operation has been explicitly overridden to run on a secondary.
* This replaces previous usage of QueryOption_SlaveOk.
*/
bool isSecondaryOk() const;
/**
* Returns the ReadPreference associated with this operation. See
* mongo/client/read_preference.h for further details.
*/
const boost::optional<ReadPreferenceSetting>& getReadPreference() const;
private:
ServerSelectionMetadata(bool secondaryOk,
boost::optional<ReadPreferenceSetting> readPreference);
bool _secondaryOk{false};
boost::optional<ReadPreferenceSetting> _readPreference{};
};
} // namespace rpc
} // namespace mongo
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