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/**
* Copyright (C) 2019-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/db/operation_context.h"
#include "mongo/s/request_types/rename_collection_gen.h"
#include "mongo/util/string_map.h"
namespace mongo {
class ScopedRenameCollection;
/**
* Thread-safe object that keeps track of any active renameCollection commands running. There is
* only one instance of this object per shard.
*/
class ActiveRenameCollectionRegistry {
ActiveRenameCollectionRegistry(const ActiveRenameCollectionRegistry&) = delete;
ActiveRenameCollectionRegistry& operator=(const ActiveRenameCollectionRegistry&) = delete;
public:
ActiveRenameCollectionRegistry();
~ActiveRenameCollectionRegistry();
static ActiveRenameCollectionRegistry& get(ServiceContext* service);
static ActiveRenameCollectionRegistry& get(OperationContext* opCtx);
/**
* If the collection being requested to be renamed is not already being renamed on this shard,
* registers an active renameCollection with the specified arguments. Returns a
* ScopedRenameCollection object, which must be signaled by the caller before it goes out of
* scope.
*
* If this collection is already being renamed on this shard and it has the exact same
* arguments, returns a ScopedRenameCollection. The ScopedRenameCollection can be used to join
* the already running shard collection.
*
* Otherwise returns a ConflictingOperationInProgress error.
*/
StatusWith<ScopedRenameCollection> registerRenameCollection(
const ShardsvrRenameCollection& request);
private:
friend class ScopedRenameCollection;
// Describes the state of a currently active renameCollection operation
struct ActiveRenameCollectionState {
ActiveRenameCollectionState(ShardsvrRenameCollection inRequest)
: activeRequest(std::move(inRequest)) {}
/**
* Constructs an error status to return in the case of conflicting operations.
*/
Status constructErrorStatus(const ShardsvrRenameCollection& request) const;
// Exact arguments of the currently active operation
ShardsvrRenameCollection activeRequest;
/**
* Promise that will either be set with an error or emplaced with nothing. Used to
* follow an async/await paradigm when trying to join duplicate requests.
*/
SharedPromise<void> _promise;
};
/**
* Unregisters a previously registered namespace with an ongoing renameCollection. Must only be
* called if a previous call to registerRenameCollection has succeeded.
*/
void _clearRenameCollection(std::string nss);
// Fulfills the promise and emplaces nothing on the promise if the status is OK or sets an
// error on the promise if it is not.
void _setEmptyOrError(std::string nss, Status status);
// Protects the state below
stdx::mutex _mutex;
// Map containing any collections currently being renamed
StringMap<std::shared_ptr<ActiveRenameCollectionState>> _activeRenameCollectionMap;
};
/**
* Object of this class is returned from the registerRenameCollection call of the active rename
* collection registry. It can exist in two modes - 'execute' and 'join'. See the comments for
* registerRenameCollection method for more details.
*/
class ScopedRenameCollection {
ScopedRenameCollection(const ScopedRenameCollection&) = delete;
ScopedRenameCollection& operator=(const ScopedRenameCollection&) = delete;
public:
ScopedRenameCollection(std::string nss,
ActiveRenameCollectionRegistry* registry,
bool shouldExecute,
SharedSemiFuture<void> uuidFuture);
~ScopedRenameCollection();
ScopedRenameCollection(ScopedRenameCollection&&);
ScopedRenameCollection& operator=(ScopedRenameCollection&&);
/**
* Returns true if the renameCollection object is in the 'execute' mode. This means that the
* caller can execute the renameCollection command. The holder must execute the command and
* get the status from the promise.
*/
bool mustExecute() const {
return _shouldExecute;
}
/**
* Must only be called if the object is in the 'execute' mode when the renameCollection command
* was invoked (the command immediately executed). Will either set error if status is not OK or
* emplace an empty value into promise.
*/
void emplaceStatus(Status status);
/**
* Must only be called if the object is in the 'join' mode. Gets a future for the collection.
*/
SharedSemiFuture<void> awaitExecution();
private:
// Namespace of collection being renamed
std::string _nss;
// Registry from which to unregister the rename. Not owned.
ActiveRenameCollectionRegistry* _registry;
/**
* Whether the holder is the first in line for a newly started renameCollection (in which case
* the destructor must unregister) or the caller is joining on an already-running
* renameCollection (in which case the caller must block and wait for completion).
*/
bool _shouldExecute;
// Future that will be signaled at the end of renameCollection.
SharedSemiFuture<void> _future;
};
} // namespace mongo
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