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/**
* Copyright (C) 2017 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 <boost/optional.hpp>
#include <map>
#include <memory>
#include "mongo/base/disallow_copying.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/repl/optime.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
class OperationContext;
class ServiceContext;
namespace repl {
class StorageInterface;
/**
* This class manages collections that are marked as drop-pending by the 2-phase algorithm.
*
* Replicated collections that are dropped are not permanently removed from the storage system
* when the drop collection request is first processed. Instead, the collection is renamed to a
* hidden collection in the same database with a special namespace (<db>.system.drop.*).
*
* On receiving a notification in the replica set state (eg. commit level), some drop-pending
* with drop optimes will become safe to remove permanently. This class provides the function
* dropCollectionsOlderThan() for this purpose.
*/
class DropPendingCollectionReaper {
MONGO_DISALLOW_COPYING(DropPendingCollectionReaper);
public:
// Operation Context binding.
static DropPendingCollectionReaper* get(ServiceContext* service);
static DropPendingCollectionReaper* get(ServiceContext& service);
static DropPendingCollectionReaper* get(OperationContext* opCtx);
static void set(ServiceContext* service,
std::unique_ptr<DropPendingCollectionReaper> storageInterface);
// Container type for drop-pending namespaces. We use a multimap so that we can order the
// namespaces by drop optime. Additionally, it is possible for certain user operations (such
// as renameCollection across databases) to generate more than one drop-pending namespace for
// the same drop optime.
using DropPendingNamespaces = std::multimap<OpTime, NamespaceString>;
explicit DropPendingCollectionReaper(StorageInterface* storageInterface);
virtual ~DropPendingCollectionReaper() = default;
/**
* Adds a new drop-pending namespace, with its drop optime, to be managed by this class.
*/
void addDropPendingNamespace(const OpTime& dropOpTime,
const NamespaceString& dropPendingNamespace);
/**
* Returns earliest drop optime in '_dropPendingNamespaces'.
* Returns boost::none if '_dropPendingNamespaces' is empty.
*/
boost::optional<OpTime> getEarliestDropOpTime();
/**
* Notifies this class of a change in the replica set state (eg. commit level).
* Drops all drop-pending namespaces with drop optimes before or at 'opTime'.
* After this function returns, all entries in '_dropPendingNamespaces' will have drop
* optimes more recent than 'opTime'.
*/
void dropCollectionsOlderThan(OperationContext* opCtx, const OpTime& opTime);
void clearDropPendingState() {
stdx::lock_guard<stdx::mutex> lock(_mutex);
_dropPendingNamespaces.clear();
}
/**
* Renames the drop-pending namespace at the specified optime back to the provided name.
* There can only be one matching collection per database and at most two entries per optime
* (due to renameCollection across databases).
* We cannot reconstruct the original namespace so we must get it passed in. It accepts the
* fully qualified namespace so that we can locate the correct entry by optime and database.
* This function also removes the entry from '_dropPendingNamespaces'.
* This function returns false if there is no drop-pending collection at the specified optime.
*/
bool rollBackDropPendingCollection(OperationContext* opCtx,
const OpTime& opTime,
const NamespaceString& collectionNamespace);
private:
// All member variables are labeled with one of the following codes indicating the
// synchronization rules for accessing them.
//
// (R) Read-only in concurrent operation; no synchronization required.
// (S) Self-synchronizing; access in any way from any context.
// (M) Reads and writes guarded by _mutex.
// Guards access to member variables.
stdx::mutex _mutex;
// Used to access the storage layer.
StorageInterface* const _storageInterface; // (R)
// Drop-pending namespaces. Ordered by drop optime.
DropPendingNamespaces _dropPendingNamespaces; // (M)
};
} // namespace repl
} // namespace mongo
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