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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 <string>
#include "mongo/base/disallow_copying.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/bson/oid.h"
#include "mongo/db/s/migration_session_id.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/mutex.h"
#include "mongo/stdx/thread.h"
#include "mongo/util/timer.h"
namespace mongo {
class NamespaceString;
class OperationContext;
class Status;
struct WriteConcernOptions;
namespace repl {
class OpTime;
}
/**
* Drives the receiving side of the MongoD migration process. One instance exists per shard.
*/
class MigrationDestinationManager {
MONGO_DISALLOW_COPYING(MigrationDestinationManager);
public:
enum State { READY, CLONE, CATCHUP, STEADY, COMMIT_START, DONE, FAIL, ABORT };
MigrationDestinationManager();
~MigrationDestinationManager();
State getState() const;
void setState(State newState);
bool isActive() const;
/**
* Reports the state of the migration manager as a BSON document.
*/
void report(BSONObjBuilder& b);
/**
* Returns OK if migration started successfully.
*/
Status start(const std::string& ns,
const MigrationSessionId& sessionId,
const std::string& fromShard,
const BSONObj& min,
const BSONObj& max,
const BSONObj& shardKeyPattern,
const OID& epoch,
const WriteConcernOptions& writeConcern);
void abort();
bool startCommit(const MigrationSessionId& sessionId);
private:
/**
* Thread which drives the migration apply process on the recipient side.
*/
void _migrateThread(std::string ns,
MigrationSessionId sessionId,
BSONObj min,
BSONObj max,
BSONObj shardKeyPattern,
std::string fromShard,
OID epoch,
WriteConcernOptions writeConcern);
void _migrateDriver(OperationContext* txn,
const std::string& ns,
const MigrationSessionId& sessionId,
const BSONObj& min,
const BSONObj& max,
const BSONObj& shardKeyPattern,
const std::string& fromShard,
const OID& epoch,
const WriteConcernOptions& writeConcern);
bool _applyMigrateOp(OperationContext* txn,
const std::string& ns,
const BSONObj& min,
const BSONObj& max,
const BSONObj& shardKeyPattern,
const BSONObj& xfer,
repl::OpTime* lastOpApplied);
bool _flushPendingWrites(OperationContext* txn,
const std::string& ns,
BSONObj min,
BSONObj max,
const repl::OpTime& lastOpApplied,
const WriteConcernOptions& writeConcern);
/**
* Remembers a chunk range between 'min' and 'max' as a range which will have data migrated
* into it. This data can then be protected against cleanup of orphaned data.
*
* Overlapping pending ranges will be removed, so it is only safe to use this when you know
* your metadata view is definitive, such as at the start of a migration.
*
* TODO: Because migrations may currently be active when a collection drops, an epoch is
* necessary to ensure the pending metadata change is still applicable.
*/
Status _notePending(OperationContext* txn,
const NamespaceString& nss,
const BSONObj& min,
const BSONObj& max,
const OID& epoch);
/**
* Stops tracking a chunk range between 'min' and 'max' that previously was having data
* migrated into it. This data is no longer protected against cleanup of orphaned data.
*
* To avoid removing pending ranges of other operations, ensure that this is only used when
* a migration is still active.
*
* TODO: Because migrations may currently be active when a collection drops, an epoch is
* necessary to ensure the pending metadata change is still applicable.
*/
Status _forgetPending(OperationContext* txn,
const NamespaceString& nss,
const BSONObj& min,
const BSONObj& max,
const OID& epoch);
// Mutex to guard all fields
mutable stdx::mutex _mutex;
// Migration session ID uniquely identifies the migration and indicates whether the prepare
// method has been called.
boost::optional<MigrationSessionId> _sessionId{boost::none};
// A condition variable on which to wait for the prepare method to be called.
stdx::condition_variable _isActiveCV;
stdx::thread _migrateThreadHandle;
std::string _ns;
std::string _from;
BSONObj _min;
BSONObj _max;
BSONObj _shardKeyPattern;
// Set to true once we have accepted the chunk as pending into our metadata. Used so that on
// failure we can perform the appropriate cleanup.
bool _chunkMarkedPending{false};
long long _numCloned{0};
long long _clonedBytes{0};
long long _numCatchup{0};
long long _numSteady{0};
State _state{READY};
std::string _errmsg;
};
} // namespace mongo
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