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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 <memory>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/status.h"
#include "mongo/base/status_with.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/repl/optime.h"
#include "mongo/db/repl/replication_consistency_markers.h"
#include "mongo/db/repl/replication_recovery.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
class OperationContext;
class ServiceContext;
namespace repl {
class StorageInterface;
/**
* This class represents the current replication process state that is used during the replication
* of operations from the sync source to the current node.
*
* For example, the rollback ID, which is persisted to storage, is cached here for the purposes of
* filling in the metadata for the find/getMore queries used to tail the oplog on the sync source.
*
* This class DOES NOT hold any information related to the consensus protocol.
*/
class ReplicationProcess {
MONGO_DISALLOW_COPYING(ReplicationProcess);
public:
/**
* Contains at most one document representing the progress of the current rollback process.
*
* Schema:
* {_id: "rollbackProgress", applyUntil: <optime>}
*
* '_id' is always "rollbackProgress".
*
* 'applyUntil' contains the optime of the last oplog entry from the sync source that we need to
* apply in order to complete rollback successfully.
*/
static const NamespaceString kRollbackProgressNamespace;
// Operation Context binding.
static ReplicationProcess* get(ServiceContext* service);
static ReplicationProcess* get(ServiceContext& service);
static ReplicationProcess* get(OperationContext* opCtx);
static void set(ServiceContext* service, std::unique_ptr<ReplicationProcess> process);
ReplicationProcess(StorageInterface* storageInterface,
std::unique_ptr<ReplicationConsistencyMarkers> consistencyMarkers,
std::unique_ptr<ReplicationRecovery> recovery);
virtual ~ReplicationProcess() = default;
/**
* Rollback ID is an increasing counter of how many rollbacks have occurred on this server.
*/
StatusWith<int> getRollbackID(OperationContext* opCtx);
Status initializeRollbackID(OperationContext* opCtx);
Status incrementRollbackID(OperationContext* opCtx);
/**
* Rollback progress is set after we have retrieved all the information from the sync source
* that we need to complete rollback without further communication with the sync source.
* Rollback progress is cleared when rollback has completed successfully. This information is
* stored in the 'kRollbackProgressNamespace' collection.
* If the collection is not empty, it will hold the optime of the oplog entry we pulled down
* from the sync source into the local.system.rollback.oplog collection that we need to apply
* through from that collection. It is safe to exit rollback once we have applied this optime.
*
* If the collection is not present, we return NamespaceNotFound.
* If the document is not present, we return NoSuchKey.
*
* This function is used at replication startup to check if a previously interrupted rollback
* process has occurred and that the rollback process can be resumed without contacting any
* sync source.
* An error status returned by this function indicates that we did not detect any interrupted
* rollback and that we can continue with normal replication startup.
*/
StatusWith<OpTime> getRollbackProgress(OperationContext* opCtx);
/**
* Upon success, a document representing the current rollback progress will be present in the
* 'kRollbackProgressNamespace' collection. This document will contain the optime that this
* node will have to reach in order to consider rollback complete.
*
* If the 'kRollbackProgressNamespace' collection is not present when this function is called,
* this function will create it before inserting the document.
*/
Status setRollbackProgress(OperationContext* opCtx, const OpTime& applyUntil);
/**
* Removes the rollback progress document from the 'kRollbackProgressNamespace' collection.
*
* If the collection is not found, this function will return a successful Status because there's
* nothing further to do.
*/
Status clearRollbackProgress(OperationContext* opCtx);
/**
* Returns an object used for operating on the documents that maintain replication consistency.
*/
ReplicationConsistencyMarkers* getConsistencyMarkers();
/**
* Returns an object used to recover from the oplog on startup or rollback.
*/
ReplicationRecovery* getReplicationRecovery();
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)
// Used for operations on documents that maintain replication consistency.
std::unique_ptr<ReplicationConsistencyMarkers> _consistencyMarkers; // (S)
std::unique_ptr<ReplicationRecovery> _recovery; // (S)
// Rollback ID. This is a cached copy of the persisted value in the local.system.rollback.id
// collection.
int _rbid; // (M)
};
} // namespace repl
} // namespace mongo
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