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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/repl/storage_interface.h"
#include "mongo/db/server_options.h"
namespace mongo {
class BSONObj;
class OperationContext;
class FeatureCompatibilityVersion {
public:
/**
* Should be taken in shared mode by any operations that should not run while
* setFeatureCompatibilityVersion is running.
*
* setFCV takes this lock in exclusive mode so that it both does not run with the shared mode
* operations and does not run with itself.
*/
static Lock::ResourceMutex fcvLock;
/**
* Records intent to perform a 4.4 -> 4.6 upgrade by updating the on-disk feature
* compatibility version document to have 'version'=4.4, 'targetVersion'=4.6.
* Should be called before schemas are modified.
*/
static void setTargetUpgrade(OperationContext* opCtx);
/**
* Records intent to perform a 4.6 -> 4.4 downgrade by updating the on-disk feature
* compatibility version document to have 'version'=4.4, 'targetVersion'=4.4.
* Should be called before schemas are modified.
*/
static void setTargetDowngrade(OperationContext* opCtx);
/**
* Records the completion of a 4.4 <-> 4.6 upgrade or downgrade by updating the on-disk feature
* compatibility version document to have 'version'=version and unsetting the 'targetVersion'
* field. Should be called after schemas are modified.
*/
static void unsetTargetUpgradeOrDowngrade(OperationContext* opCtx, StringData version);
/**
* 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();
/**
* Examines a document inserted or updated in the server configuration collection
* (admin.system.version). If it is the featureCompatibilityVersion document, validates the
* document and on commit, updates the server parameter.
*/
static void onInsertOrUpdate(OperationContext* opCtx, const BSONObj& doc);
/**
* Sets the server's outgoing and incomingInternalClient minWireVersions according to the
* current featureCompatibilityVersion value.
*/
static void updateMinWireVersion();
/**
* Ensures the in-memory and on-disk FCV states are consistent after a rollback.
*/
static void onReplicationRollback(OperationContext* opCtx);
private:
/**
* Validate version. Uasserts if invalid.
*/
static void _validateVersion(StringData version);
/**
* Build update command.
*/
typedef std::function<void(BSONObjBuilder)> UpdateBuilder;
static void _runUpdateCommand(OperationContext* opCtx, UpdateBuilder callback);
/**
* Set the FCV to newVersion, making sure to close any outgoing connections with incompatible
* servers and closing open transactions if necessary. Increments the server TopologyVersion.
*/
static void _setVersion(OperationContext* opCtx,
ServerGlobalParams::FeatureCompatibility::Version newVersion);
};
/**
* Utility class to prevent the FCV from changing while the FixedFCVRegion is in scope.
*/
class FixedFCVRegion {
public:
explicit FixedFCVRegion(OperationContext* opCtx) {
invariant(!opCtx->lockState()->isLocked());
_lk.emplace(opCtx->lockState(), FeatureCompatibilityVersion::fcvLock);
}
~FixedFCVRegion() = default;
void release() {
_lk.reset();
}
private:
boost::optional<Lock::SharedLock> _lk;
};
} // namespace mongo
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