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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 <list>
#include <set>
#include <string>
#include "mongo/base/disallow_copying.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/db/namespace_string.h"
#include "mongo/stdx/condition_variable.h"
namespace mongo {
class BSONObj;
class Database;
class OperationContext;
class PlanExecutor;
class RecordId;
class MigrationSourceManager {
MONGO_DISALLOW_COPYING(MigrationSourceManager);
public:
MigrationSourceManager();
~MigrationSourceManager();
/**
* Returns false if cannot start. One of the reason for not being able to start is there is
* already an existing migration in progress.
*/
bool start(OperationContext* txn,
const std::string& ns,
const BSONObj& min,
const BSONObj& max,
const BSONObj& shardKeyPattern);
void done(OperationContext* txn);
void logOp(OperationContext* txn,
const char* opstr,
const char* ns,
const BSONObj& obj,
BSONObj* patt,
bool notInActiveChunk);
bool isInMigratingChunk(const NamespaceString& ns, const BSONObj& doc);
/**
* Called from the source of a migration process, this method transfers the accummulated local
* mods from source to destination.
*/
bool transferMods(OperationContext* txn, std::string& errmsg, BSONObjBuilder& b);
/**
* Get the disklocs that belong to the chunk migrated and sort them in _cloneLocs (to avoid
* seeking disk later).
*
* @param maxChunkSize number of bytes beyond which a chunk's base data (no indices) is
* considered too large to move
* @param errmsg filled with textual description of error if this call return false
*
* Returns false if approximate chunk size is too big to move or true otherwise.
*/
bool storeCurrentLocs(OperationContext* txn,
long long maxChunkSize,
std::string& errmsg,
BSONObjBuilder& result);
bool clone(OperationContext* txn, std::string& errmsg, BSONObjBuilder& result);
void aboutToDelete(const RecordId& dl);
std::size_t cloneLocsRemaining() const;
long long mbUsed() const;
bool getInCriticalSection() const;
void setInCriticalSection(bool inCritSec);
/**
* Blocks until the "in critical section" state changes and returns true if we are NOT in the
* critical section
*/
bool waitTillNotInCriticalSection(int maxSecondsToWait);
bool isActive() const;
private:
friend class LogOpForShardingHandler;
/**
* Insert items from docIdList to a new array with the given fieldName in the given builder. If
* explode is true, the inserted object will be the full version of the document. Note that the
* whenever an item from the docList is inserted to the array, it will also be removed from
* docList.
*
* Should be holding the collection lock for ns if explode is true.
*/
void _xfer(OperationContext* txn,
const std::string& ns,
Database* db,
std::list<BSONObj>* docIdList,
BSONObjBuilder& builder,
const char* fieldName,
long long& size,
bool explode);
NamespaceString _getNS() const;
// All member variables are labeled with one of the following codes indicating the
// synchronization rules for accessing them.
//
// (M) Must hold _mutex for access.
// (MG) For reads, _mutex *OR* Global IX Lock must be held.
// For writes, the _mutex *AND* (Global Shared or Exclusive Lock) must be held.
// (C) Must hold _cloneLocsMutex for access.
//
// Locking order:
//
// Global Lock -> _mutex -> _cloneLocsMutex
mutable stdx::mutex _mutex;
stdx::condition_variable _inCriticalSectionCV; // (M)
// Is migration currently in critical section. This can be used to block new writes.
bool _inCriticalSection{false}; // (M)
std::unique_ptr<PlanExecutor> _deleteNotifyExec; // (M)
// List of _id of documents that were modified that must be re-cloned.
std::list<BSONObj> _reload; // (M)
// List of _id of documents that were deleted during clone that should be deleted later.
std::list<BSONObj> _deleted; // (M)
// Bytes in _reload + _deleted
long long _memoryUsed{0}; // (M)
// If a migration is currently active.
bool _active{false}; // (MG)
NamespaceString _nss; // (MG)
BSONObj _min; // (MG)
BSONObj _max; // (MG)
BSONObj _shardKeyPattern; // (MG)
mutable stdx::mutex _cloneLocsMutex;
// List of record id that needs to be transferred from here to the other side.
std::set<RecordId> _cloneLocs; // (C)
};
} // namespace mongo
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