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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 "mongo/base/status_with.h"
#include "mongo/base/string_data.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/db/commands/feature_compatibility_version_document_gen.h"
#include "mongo/db/commands/set_feature_compatibility_version_gen.h"
#include "mongo/db/repl/storage_interface.h"
#include "mongo/db/server_options.h"
namespace mongo {
class FeatureCompatibilityVersion {
public:
/**
* Reads the featureCompatibilityVersion (FCV) document in admin.system.version and initializes
* the FCV global state. Returns an error if the FCV document exists and is invalid. Does not
* return an error if it is missing. This should be checked after startup with
* fassertInitializedAfterStartup.
*
* Throws a MustDowngrade error if an existing FCV document contains an invalid version.
*/
static void initializeForStartup(OperationContext* opCtx);
/**
* Fatally asserts if the featureCompatibilityVersion is not properly initialized after startup.
*/
static void fassertInitializedAfterStartup(OperationContext* opCtx);
/**
* Returns the on-disk feature compatibility version document if it exists.
*/
static boost::optional<BSONObj> findFeatureCompatibilityVersionDocument(
OperationContext* opCtx);
/**
* uassert that a transition from fromVersion to newVersion is permitted. Different rules apply
* if the request is from a config server.
*/
static void validateSetFeatureCompatibilityVersionRequest(
OperationContext* opCtx,
const SetFeatureCompatibilityVersion& setFCVRequest,
multiversion::FeatureCompatibilityVersion fromVersion);
/**
* Updates the on-disk feature compatibility version document for the transition fromVersion ->
* newVersion. This is required to be a valid transition.
*/
static void updateFeatureCompatibilityVersionDocument(
OperationContext* opCtx,
multiversion::FeatureCompatibilityVersion fromVersion,
multiversion::FeatureCompatibilityVersion newVersion,
bool isFromConfigServer,
boost::optional<Timestamp> timestamp,
bool setTargetVersion);
/**
* If there are no non-local databases, store the featureCompatibilityVersion document. If we
* are not running with --shardsvr, set the version to be the upgrade value. If we are running
* with --shardsvr, set the version to be the downgrade value.
*/
static void setIfCleanStartup(OperationContext* opCtx,
repl::StorageInterface* storageInterface);
/**
* Returns true if the server is on a clean startup. A clean startup means there are no
* databases on disk besides the local database.
*/
static bool isCleanStartUp();
/**
* Sets the server's outgoing and incomingInternalClient minWireVersions according to the
* current featureCompatibilityVersion value.
*/
static void updateMinWireVersion();
/**
* Returns a scoped object, which holds the 'fcvLock' in exclusive mode for the given scope. It
* must only be used by the setFeatureCompatibilityVersion command in order to serialise with
* concurrent 'FixedFCVRegions'.
*/
static Lock::ExclusiveLock enterFCVChangeRegion(OperationContext* opCtx);
/**
* Used by the FCV OpObserver to set the timestamp of the last opTime where the FCV was updated.
* We use this to ensure the user does not see a non-transitional FCV that is not in the
* majority snapshot, since upgrading or downgrading will not work in that circumstance.
*/
static void advanceLastFCVUpdateTimestamp(Timestamp fcvUpdateTimestamp);
/**
* Used by the FCV OpObserver at rollback time. The rollback FCV is always in the
* majority snapshot, so it is safe to clear the lastFCVUpdateTimestamp then.
*
* Also used in rare cases when the replication coordinator majority snapshot is cleared.
*/
static void clearLastFCVUpdateTimestamp();
};
/**
* Utility class to prevent the FCV from changing while the FixedFCVRegion is in scope.
*/
class FixedFCVRegion {
public:
explicit FixedFCVRegion(OperationContext* opCtx);
~FixedFCVRegion();
bool operator==(const multiversion::FeatureCompatibilityVersion& other) const;
bool operator!=(const multiversion::FeatureCompatibilityVersion& other) const;
const ServerGlobalParams::FeatureCompatibility& operator*() const;
const ServerGlobalParams::FeatureCompatibility* operator->() const;
private:
Lock::SharedLock _lk;
};
} // namespace mongo
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