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/**
* Copyright (C) 2008-2015 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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 <string>
#include "mongo/db/repl/optime.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/s/shard_id.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
class ChunkManager;
struct CollectionInfo;
class DatabaseType;
class OperationContext;
/**
* Represents the cache entry for a database.
*/
class DBConfig {
public:
DBConfig(const DatabaseType& dbt, repl::OpTime configOpTime);
~DBConfig();
/**
* The name of the database which this entry caches.
*/
const std::string& name() const {
return _name;
}
ShardId getPrimaryId();
/**
* Returns whether 'enableSharding' has been called for this database.
*/
bool isShardingEnabled() const {
return _shardingEnabled;
}
/**
* Removes the specified namespace from the set of collections under this database entry so that
* from then onwards it will be treated as unsharded.
*
* Note that this method doesn't do any writes to the config metadata, but simply drops the
* specified namespace from the cache.
*/
void markNSNotSharded(const std::string& ns);
/**
* @return whether or not the 'ns' collection is partitioned
*/
bool isSharded(const std::string& ns);
std::shared_ptr<ChunkManager> getChunkManager(OperationContext* txn,
const std::string& ns,
bool reload = false,
bool forceReload = false);
std::shared_ptr<ChunkManager> getChunkManagerIfExists(OperationContext* txn,
const std::string& ns,
bool reload = false,
bool forceReload = false);
/**
* Returns true if it is successful at loading the DBConfig, false if the database is not found,
* and throws on all other errors.
*/
bool load(OperationContext* txn);
protected:
typedef std::map<std::string, CollectionInfo> CollectionInfoMap;
typedef AtomicUInt64::WordType Counter;
/**
* Returns true if it is successful at loading the DBConfig, false if the database is not found,
* and throws on all other errors.
* Also returns true without reloading if reloadIteration is not equal to the _reloadCount.
* This is to avoid multiple threads attempting to reload do duplicate work.
*/
bool _loadIfNeeded(OperationContext* txn, Counter reloadIteration);
// All member variables are labeled with one of the following codes indicating the
// synchronization rules for accessing them.
//
// (L) Must hold _lock for access.
// (S) Self synchronizing, no explicit locking needed.
//
// Mutex lock order:
// _hitConfigServerLock -> _lock
//
// Name of the database which this entry caches
const std::string _name;
// Whether sharding is enabled for this database
const bool _shardingEnabled;
// Primary shard id
ShardId _primaryId; // (L)
// Set of collections and lock to protect access
stdx::mutex _lock;
CollectionInfoMap _collections; // (L)
// OpTime of config server when the database definition was loaded.
repl::OpTime _configOpTime; // (L)
// Ensures that only one thread at a time loads collection configuration data from
// the config server
stdx::mutex _hitConfigServerLock;
// Increments every time this performs a full reload. Since a full reload can take a very
// long time for very large clusters, this can be used to minimize duplicate work when multiple
// threads tries to perform full rerload at roughly the same time.
AtomicUInt64 _reloadCount; // (S)
};
} // namespace mongo
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