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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/bson/bsonobj.h"
#include "mongo/db/s/sharding_migration_critical_section.h"
#include "mongo/db/s/sharding_state_lock.h"
#include "mongo/s/catalog/type_database_gen.h"
namespace mongo {
class MovePrimarySourceManager;
class OperationContext;
/**
* Synchronizes access to this shard server's cached database version for Database.
*/
class DatabaseShardingState {
DatabaseShardingState(const DatabaseShardingState&) = delete;
DatabaseShardingState& operator=(const DatabaseShardingState&) = delete;
public:
/**
* A ShardingStateLock is used on DatabaseShardingState operations in order to ensure
* synchronization across operations.
*/
using DSSLock = ShardingStateLock<DatabaseShardingState>;
DatabaseShardingState(StringData dbName);
~DatabaseShardingState() = default;
/**
* Obtains the sharding state for the specified database. If it does not exist, it will be
* created and will remain in memory until the database is dropped.
*
* Must be called with some lock held on the database being looked up and the returned
* pointer must not be stored.
*/
static DatabaseShardingState* get(OperationContext* opCtx, StringData dbName);
/**
* Obtain a pointer to the DatabaseShardingState that remains safe to access without holding
* a database lock. Should be called instead of the regular get() if no database lock is held.
* The returned DatabaseShardingState instance should not be modified!
*/
static std::shared_ptr<DatabaseShardingState> getSharedForLockFreeReads(OperationContext* opCtx,
StringData dbName);
/**
* Methods to control the databases's critical section. Must be called with the database X lock
* held.
*/
void enterCriticalSectionCatchUpPhase(OperationContext* opCtx, DSSLock&, const BSONObj& reason);
void enterCriticalSectionCommitPhase(OperationContext* opCtx, DSSLock&, const BSONObj& reason);
void exitCriticalSection(OperationContext* opCtx, const BSONObj& reason);
auto getCriticalSectionSignal(ShardingMigrationCriticalSection::Operation op, DSSLock&) const {
return _critSec.getSignal(op);
}
auto getCriticalSectionReason(DSSLock&) const {
return _critSec.getReason() ? _critSec.getReason()->toString() : "Unknown";
}
/**
* Returns the active movePrimary source manager, if one is available.
*/
MovePrimarySourceManager* getMovePrimarySourceManager(DSSLock&);
/**
* Attaches a movePrimary source manager to this database's sharding state. Must be called with
* the database lock in X mode. May not be called if there is a movePrimary source manager
* already installed. Must be followed by a call to clearMovePrimarySourceManager.
*/
void setMovePrimarySourceManager(OperationContext* opCtx,
MovePrimarySourceManager* sourceMgr,
DSSLock&);
/**
* Removes a movePrimary source manager from this database's sharding state. Must be called with
* with the database lock in X mode. May not be called if there isn't a movePrimary source
* manager installed already through a previous call to setMovePrimarySourceManager.
*/
void clearMovePrimarySourceManager(OperationContext* opCtx);
private:
friend DSSLock;
// Object-wide ResourceMutex to protect changes to the DatabaseShardingState or objects held
// within.
Lock::ResourceMutex _stateChangeMutex{"DatabaseShardingState"};
const std::string _dbName;
// Modifying the state below requires holding the DBLock in X mode; holding the DBLock in any
// mode is acceptable for reading it. (Note: accessing this class at all requires holding the
// DBLock in some mode).
ShardingMigrationCriticalSection _critSec;
// If this database is serving as a source shard for a movePrimary, the source manager will be
// non-null. To write this value, there needs to be X-lock on the database in order to
// synchronize with other callers which will read the source manager.
//
// NOTE: The source manager is not owned by this class.
MovePrimarySourceManager* _sourceMgr{nullptr};
};
} // namespace mongo
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