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/**
* Copyright (C) 2020-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 "mongo/base/status.h"
#include "mongo/base/string_data.h"
#include "mongo/bson/bsonelement.h"
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/db/read_write_concern_provenance_base_gen.h"
namespace mongo {
/**
* This class represents the "provenance" (ie. original source) of a read or write concern.
*
* This information is serialized as a 'provenance' field inside readConcern/writeConcern objects,
* which is parsed, stored, and forwarded, but has no other effect on the meaning of the read or
* write concern (RWC). This means it is possible to see (in logs, currentOp, profiling, etc) where
* a given RWC has come from. It also makes it possible for the server to adjust its behavior based
* on the origin of the RWC (even though the semantics of the RWC itself have not changed), for
* example, by having special metrics that only apply to RWC from certain sources.
*
* Possible sources are:
*
* - unset (ie. the 'provenance' field was absent):
* Implicitly means "clientSupplied" (so drivers do not need to send a 'provenance' field).
*
* - "clientSupplied":
* The RWC was originally explicitly passed to a mongos or plain replica set member by the
* driver.
*
* - "implicitDefault":
* The client did not supply an explicit RWC, and there was no RWC default, so this RWC
* represents the corresponding implicit server default, ie. read concern of "local" (except
* "available" on sharded secondaries) and {w: 1, wtimeout: 0}.
*
* - "customDefault":
* Represents an admin-defined cluster-wide RWC default that was applied to the operation
* because no explicit RWC was provided, and there was a custom RWC default defined at the time.
*
* - "getLastErrorDefaults":
* Only applicable to write concern, and indicates that it originated from the (deprecated)
* 'settings.getLastErrorDefaults' field of the replica set configuration.
*
* - "internalWriteDefault":
* Only applicable to write concern on internal writes, and indicates that the internal client
* did not supply an explicit write concern, so this write concern represents the corresponding
* server default for internal writes, ie. {w: 1, wtimeout: 0}.
*
* A ReadWriteConcernProvenance object may only have a single Source value throughout its lifetime;
* once the Source has been set, attempting to change it will trigger an invariant. This ensures
* the integrity of the provenance value as the operation makes its way through the server (and
* through the overall cluster).
*/
class ReadWriteConcernProvenance : public ReadWriteConcernProvenanceBase {
public:
using Source = ReadWriteConcernProvenanceSourceEnum;
static constexpr StringData kClientSupplied = "clientSupplied"_sd;
static constexpr StringData kImplicitDefault = "implicitDefault"_sd;
static constexpr StringData kCustomDefault = "customDefault"_sd;
static constexpr StringData kGetLastErrorDefaults = "getLastErrorDefaults"_sd;
static constexpr StringData kInternalWriteDefault = "internalWriteDefault"_sd;
ReadWriteConcernProvenance() = default;
ReadWriteConcernProvenance(Source source) {
setSource(source);
}
ReadWriteConcernProvenance(ReadWriteConcernProvenanceBase&& base)
: ReadWriteConcernProvenanceBase(base) {}
/**
* Returns true if this provenance has been set to an actual source, or false if it is unset.
*/
bool hasSource() const {
return static_cast<bool>(getSource());
}
/**
* Returns true if the RWC has been supplied by the client, ie. if this provenance's source is
* either unset (the client specified RWC but without provenance) or explicitly the
* "clientSupplied" source.
*/
bool isClientSupplied() const {
return !hasSource() || *getSource() == Source::clientSupplied;
}
/**
* Returns true if the RWC was an implicit default.
*/
bool isImplicitDefault() const {
return hasSource() && *getSource() == Source::implicitDefault;
}
/**
* Returns true if the RWC was a custom default.
*/
bool isCustomDefault() const {
return hasSource() && *getSource() == Source::customDefault;
}
/**
* Sets the source of this provenance. In order to prevent accidental clobbering of provenance
* with incorrect values, a source cannot change during the provenance's lifetime, except for
* the initial transition from kUnset to some other Source value.
*
* Apart from the initial transition from kUnset to some other Source value, the source of a
* provenance must not be changed during its lifetime, and this function enforces that property
* with an invariant. This is to prevent provenances from being accidentally clobbered with
* incorrect values.
*/
void setSource(boost::optional<Source> source) &;
/**
* Creates a provenance with source according to the given object's 'provenance' field.
*/
static ReadWriteConcernProvenance parse(const IDLParserContext& ctxt,
const BSONObj& bsonObject);
/**
* Convenience functions.
*/
static StringData sourceToString(boost::optional<Source> source);
bool operator==(const ReadWriteConcernProvenance& other) const {
return getSource() == other.getSource();
}
bool operator!=(const ReadWriteConcernProvenance& other) const {
return !operator==(other);
}
};
} // namespace mongo
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