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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 <string>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/string_data.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/s/metadata_manager.h"
namespace mongo {
class BSONObj;
struct ChunkVersion;
class CollectionMetadata;
class MigrationSourceManager;
class OperationContext;
/**
* Contains all sharding-related runtime state for a given collection. One such object is assigned
* to each sharded collection known on a mongod instance. A set of these objects is linked off the
* instance's sharding state.
*
* Synchronization rules: In order to look-up this object in the instance's sharding map, one must
* have some lock on the respective collection.
*/
class CollectionShardingState {
MONGO_DISALLOW_COPYING(CollectionShardingState);
public:
/**
* Instantiates a new per-collection sharding state as unsharded.
*/
CollectionShardingState(ServiceContext* sc, NamespaceString nss);
~CollectionShardingState();
/**
* Holds information used for tracking document removals during chunk migration.
*/
struct DeleteState {
// Contains the _id field of the document being deleted.
BSONObj idDoc;
// True if the document being deleted belongs to a chunk which is currently being migrated
// out of this shard.
bool isMigrating = false;
};
/**
* Obtains the sharding state for the specified collection. If it does not exist, it will be
* created and will remain active until the collection is dropped or unsharded.
*
* Must be called with some lock held on the specific collection being looked up and the
* returned pointer should never be stored.
*/
static CollectionShardingState* get(OperationContext* txn, const NamespaceString& nss);
static CollectionShardingState* get(OperationContext* txn, const std::string& ns);
/**
* Returns the chunk metadata for the collection.
*/
ScopedCollectionMetadata getMetadata();
/**
* Updates the metadata based on changes received from the config server and also resolves the
* pending receives map in case some of these pending receives have completed or have been
* abandoned.
*
* Must always be called with an exclusive collection lock.
*/
void refreshMetadata(OperationContext* txn, std::unique_ptr<CollectionMetadata> newMetadata);
/**
* Modifies the collection's sharding state to indicate that it is beginning to receive the
* given ChunkRange.
*/
void beginReceive(const ChunkRange& range);
/*
* Modifies the collection's sharding state to indicate that the previous pending migration
* failed. If the range was not previously pending, this function will crash the server.
*
* This function is the mirror image of beginReceive.
*/
void forgetReceive(const ChunkRange& range);
/**
* Returns the active migration source manager, if one is available.
*/
MigrationSourceManager* getMigrationSourceManager();
/**
* Attaches a migration source manager to this collection's sharding state. Must be called with
* collection X lock. May not be called if there is a migration source manager already
* installed. Must be followed by a call to clearMigrationSourceManager.
*/
void setMigrationSourceManager(OperationContext* txn, MigrationSourceManager* sourceMgr);
/**
* Removes a migration source manager from this collection's sharding state. Must be called with
* collection X lock. May not be called if there isn't a migration source manager installed
* already through a previous call to setMigrationSourceManager.
*/
void clearMigrationSourceManager(OperationContext* txn);
/**
* Checks whether the shard version in the context is compatible with the shard version of the
* collection locally and if not throws SendStaleConfigException populated with the expected and
* actual versions.
*
* Because SendStaleConfigException has special semantics in terms of how a sharded command's
* response is constructed, this function should be the only means of checking for shard version
* match.
*/
void checkShardVersionOrThrow(OperationContext* txn);
/**
* Returns whether this collection is sharded. Valid only if mongoD is primary.
* TODO SERVER-24960: This method may return a false positive until SERVER-24960 is fixed.
*/
bool collectionIsSharded();
// Replication subsystem hooks. If this collection is serving as a source for migration, these
// methods inform it of any changes to its contents.
bool isDocumentInMigratingChunk(OperationContext* txn, const BSONObj& doc);
void onInsertOp(OperationContext* txn, const BSONObj& insertedDoc);
void onUpdateOp(OperationContext* txn, const BSONObj& updatedDoc);
void onDeleteOp(OperationContext* txn, const DeleteState& deleteState);
void onDropCollection(OperationContext* txn, const NamespaceString& collectionName);
private:
friend class CollectionRangeDeleter;
/**
* Checks whether the shard version of the operation matches that of the collection.
*
* txn - Operation context from which to retrieve the operation's expected version.
* errmsg (out) - On false return contains an explanatory error message.
* expectedShardVersion (out) - On false return contains the expected collection version on this
* shard. Obtained from the operation sharding state.
* actualShardVersion (out) - On false return contains the actual collection version on this
* shard. Obtained from the collection sharding state.
*
* Returns true if the expected collection version on the shard matches its actual version on
* the shard and false otherwise. Upon false return, the output parameters will be set.
*/
bool _checkShardVersionOk(OperationContext* txn,
std::string* errmsg,
ChunkVersion* expectedShardVersion,
ChunkVersion* actualShardVersion);
// Namespace to which this state belongs.
const NamespaceString _nss;
// Contains all the metadata associated with this collection.
MetadataManager _metadataManager;
// If this collection is serving as a source shard for chunk migration, this value will be
// non-null. To write this value there needs to be X-lock on the collection in order to
// synchronize with other callers, which read it.
//
// NOTE: The value is not owned by this class.
MigrationSourceManager* _sourceMgr{nullptr};
};
} // namespace mongo
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