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/**
* Copyright (C) 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 <memory>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/string_data.h"
#include "mongo/stdx/mutex.h"
#include "mongo/util/string_map.h"
namespace mongo {
class DBConfig;
class OperationContext;
template <typename T>
class StatusWith;
/**
* This is the root of the "read-only" hierarchy of cached catalog metadata. It is read only
* in the sense that it only reads from the persistent store, but never writes to it. Instead
* writes happen through the ShardingCatalogManager and the cache hierarchy needs to be invalidated.
*/
class CatalogCache {
MONGO_DISALLOW_COPYING(CatalogCache);
public:
CatalogCache();
~CatalogCache();
/**
* Retrieves the cached metadata for the specified database. The returned value is still owned
* by the cache and should not be kept elsewhere. I.e., it should only be used as a local
* variable. The reason for this is so that if the cache gets invalidated, the caller does not
* miss getting the most up-to-date value.
*
* Returns the database cache entry if the database exists or a failed status otherwise.
*/
StatusWith<std::shared_ptr<DBConfig>> getDatabase(OperationContext* txn, StringData dbName);
/**
* Removes the database information for the specified name from the cache, so that the
* next time getDatabase is called, it will be reloaded.
*/
void invalidate(StringData dbName);
/**
* Purges all cached database information, which will cause the data to be reloaded again.
*/
void invalidateAll();
private:
using ShardedDatabasesMap = StringMap<std::shared_ptr<DBConfig>>;
// Mutex to serialize access to the structures below
stdx::mutex _mutex;
ShardedDatabasesMap _databases;
};
} // namespace mongo
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