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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 <string>
#include "mongo/base/status.h"
#include "mongo/db/json.h"
#include "mongo/db/logical_time.h"
#include "mongo/db/read_write_concern_provenance.h"
#include "mongo/db/repl/optime.h"
#include "mongo/db/repl/read_concern_level.h"
#include "mongo/util/time_support.h"
namespace mongo {
class BSONObj;
class OperationContext;
namespace repl {
class ReadConcernArgs {
public:
static constexpr StringData kReadConcernFieldName = "readConcern"_sd;
static constexpr StringData kAfterOpTimeFieldName = "afterOpTime"_sd;
static constexpr StringData kAfterClusterTimeFieldName = "afterClusterTime"_sd;
static constexpr StringData kAtClusterTimeFieldName = "atClusterTime"_sd;
static constexpr StringData kLevelFieldName = "level"_sd;
/**
* Represents the internal mechanism an operation uses to satisfy 'majority' read concern.
*/
enum class MajorityReadMechanism {
// The storage engine will read from a historical, majority committed snapshot of data. This
// is the default mechanism.
kMajoritySnapshot,
// A mechanism to be used when the storage engine does not support reading from a historical
// snapshot. A query will read from a local (potentially uncommitted) snapshot, and, after
// reading data, will block until it knows that data has become majority committed.
kSpeculative
};
static ReadConcernArgs& get(OperationContext* opCtx);
static const ReadConcernArgs& get(const OperationContext* opCtx);
ReadConcernArgs();
ReadConcernArgs(boost::optional<ReadConcernLevel> level);
ReadConcernArgs(boost::optional<OpTime> opTime, boost::optional<ReadConcernLevel> level);
ReadConcernArgs(boost::optional<LogicalTime> clusterTime,
boost::optional<ReadConcernLevel> level);
/**
* Format:
* {
* find: "coll"
* filter: <Query Object>,
* readConcern: { // optional
* level: "[majority|local|linearizable|available|snapshot]",
* afterOpTime: { ts: <timestamp>, term: <NumberLong> },
* afterClusterTime: <timestamp>,
* atClusterTime: <timestamp>
* }
* }
*/
Status initialize(const BSONObj& cmdObj) {
return initialize(cmdObj[kReadConcernFieldName]);
}
/**
* Initializes the object from the readConcern element in a command object.
* Use this if you are already iterating over the fields in the command object.
* This method correctly handles missing BSONElements.
*/
Status initialize(const BSONElement& readConcernElem);
/**
* Initializes the object by parsing the actual readConcern sub-object.
*/
Status parse(const BSONObj& readConcernObj);
static ReadConcernArgs fromBSONThrows(const BSONObj& readConcernObj);
/**
* Sets the mechanism we should use to satisfy 'majority' reads.
*
* Invalid to call unless the read concern level is 'kMajorityReadConcern'.
*/
void setMajorityReadMechanism(MajorityReadMechanism m);
/**
* Returns the mechanism to use for satisfying 'majority' read concern.
*
* Invalid to call unless the read concern level is 'kMajorityReadConcern'.
*/
MajorityReadMechanism getMajorityReadMechanism() const;
/**
* Returns whether the read concern is speculative 'majority'.
*/
bool isSpeculativeMajority() const;
/**
* Appends level, afterOpTime, and any other sub-fields in a 'readConcern' sub-object.
*/
void appendInfo(BSONObjBuilder* builder) const;
/**
* Returns true if any of clusterTime, opTime or level arguments are set. Does not differentiate
* between an unspecified read concern and an empty one (i.e. an empty BSON object).
*/
bool isEmpty() const;
/**
* Returns true if this ReadConcernArgs represents a read concern that was actually specified.
* If the RC was specified as an empty BSON object this will still be true (unlike isEmpty()).
* False represents an absent or missing read concern, ie. one which wasn't present at all.
*/
bool isSpecified() const;
/**
* Returns default kLocalReadConcern if _level is not set.
*/
ReadConcernLevel getLevel() const;
/**
* Checks whether _level is explicitly set.
*/
bool hasLevel() const;
/**
* Returns the opTime. Deprecated: will be replaced with getArgsAfterClusterTime.
*/
boost::optional<OpTime> getArgsOpTime() const;
boost::optional<LogicalTime> getArgsAfterClusterTime() const;
boost::optional<LogicalTime> getArgsAtClusterTime() const;
BSONObj toBSON() const;
BSONObj toBSONInner() const;
std::string toString() const;
ReadWriteConcernProvenance& getProvenance() {
return _provenance;
}
const ReadWriteConcernProvenance& getProvenance() const {
return _provenance;
}
private:
/**
* Appends level, afterOpTime, and the other "inner" fields of the read concern args.
*/
void _appendInfoInner(BSONObjBuilder* builder) const;
/**
* Read data after the OpTime of an operation on this replica set. Deprecated.
* The only user is for read-after-optime calls using the config server optime.
*/
boost::optional<OpTime> _opTime;
/**
* Read data after cluster-wide cluster time.
*/
boost::optional<LogicalTime> _afterClusterTime;
/**
* Read data at a particular cluster time.
*/
boost::optional<LogicalTime> _atClusterTime;
boost::optional<ReadConcernLevel> _level;
/**
* The mechanism to use for satisfying 'majority' reads. Only meaningful if the read concern
* level is 'majority'.
*/
MajorityReadMechanism _majorityReadMechanism{MajorityReadMechanism::kMajoritySnapshot};
/**
* True indicates that a read concern has been specified (even if it might be empty), as
* opposed to being absent or missing.
*/
bool _specified;
ReadWriteConcernProvenance _provenance;
};
} // namespace repl
} // namespace mongo
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