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rocksdb/include/utilities/backupable_db.h

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include "utilities/stackable_db.h"
#include "rocksdb/env.h"
#include "rocksdb/status.h"
#include <string>
#include <map>
#include <vector>
namespace rocksdb {
struct BackupableDBOptions {
// Where to keep the backup files. Has to be different than dbname_
// Best to set this to dbname_ + "/backups"
// Required
std::string backup_dir;
// Backup Env object. It will be used for backup file I/O. If it's
// nullptr, backups will be written out using DBs Env. If it's
// non-nullptr, backup's I/O will be performed using this object.
// If you want to have backups on HDFS, use HDFS Env here!
// Default: nullptr
Env* backup_env;
// If share_table_files == true, backup will assume that table files with
// same name have the same contents. This enables incremental backups and
// avoids unnecessary data copies.
// If share_table_files == false, each backup will be on its own and will
// not share any data with other backups.
// default: true
bool share_table_files;
// Backup info and error messages will be written to info_log
// if non-nullptr.
// Default: nullptr
Logger* info_log;
// If sync == true, we can guarantee you'll get consistent backup even
// on a machine crash/reboot. Backup process is slower with sync enabled.
// If sync == false, we don't guarantee anything on machine reboot. However,
// chances are some of the backups are consistent.
// Default: true
bool sync;
// If true, it will delete whatever backups there are already
// Default: false
bool destroy_old_data;
explicit BackupableDBOptions(const std::string& _backup_dir,
Env* _backup_env = nullptr,
bool _share_table_files = true,
Logger* _info_log = nullptr, bool _sync = true,
bool _destroy_old_data = false)
: backup_dir(_backup_dir),
backup_env(_backup_env),
info_log(_info_log),
sync(_sync),
destroy_old_data(_destroy_old_data) {}
};
typedef uint32_t BackupID;
struct BackupInfo {
BackupID backup_id;
int64_t timestamp;
uint64_t size;
BackupInfo() {}
BackupInfo(BackupID _backup_id, int64_t _timestamp, uint64_t _size)
: backup_id(_backup_id), timestamp(_timestamp), size(_size) {}
};
// Please see the documentation in BackupableDB and RestoreBackupableDB
class BackupEngine {
public:
virtual ~BackupEngine() {}
static BackupEngine* NewBackupEngine(Env* db_env,
const BackupableDBOptions& options);
virtual Status CreateNewBackup(DB* db, bool flush_before_backup = false) = 0;
virtual Status PurgeOldBackups(uint32_t num_backups_to_keep) = 0;
virtual Status DeleteBackup(BackupID backup_id) = 0;
virtual void StopBackup() = 0;
virtual void GetBackupInfo(std::vector<BackupInfo>* backup_info) = 0;
virtual Status RestoreDBFromBackup(BackupID backup_id,
const std::string& db_dir,
const std::string& wal_dir) = 0;
virtual Status RestoreDBFromLatestBackup(const std::string& db_dir,
const std::string& wal_dir) = 0;
};
// Stack your DB with BackupableDB to be able to backup the DB
class BackupableDB : public StackableDB {
public:
// BackupableDBOptions have to be the same as the ones used in a previous
// incarnation of the DB
//
// BackupableDB ownes the pointer `DB* db` now. You should not delete it or
// use it after the invocation of BackupableDB
BackupableDB(DB* db, const BackupableDBOptions& options);
virtual ~BackupableDB();
// Captures the state of the database in the latest backup
// NOT a thread safe call
Status CreateNewBackup(bool flush_before_backup = false);
// Returns info about backups in backup_info
void GetBackupInfo(std::vector<BackupInfo>* backup_info);
// deletes old backups, keeping latest num_backups_to_keep alive
Status PurgeOldBackups(uint32_t num_backups_to_keep);
// deletes a specific backup
Status DeleteBackup(BackupID backup_id);
// Call this from another thread if you want to stop the backup
// that is currently happening. It will return immediatelly, will
// not wait for the backup to stop.
// The backup will stop ASAP and the call to CreateNewBackup will
// return Status::Incomplete(). It will not clean up after itself, but
// the state will remain consistent. The state will be cleaned up
// next time you create BackupableDB or RestoreBackupableDB.
void StopBackup();
private:
BackupEngine* backup_engine_;
};
// Use this class to access information about backups and restore from them
class RestoreBackupableDB {
public:
RestoreBackupableDB(Env* db_env, const BackupableDBOptions& options);
~RestoreBackupableDB();
// Returns info about backups in backup_info
void GetBackupInfo(std::vector<BackupInfo>* backup_info);
// restore from backup with backup_id
// IMPORTANT -- if options_.share_table_files == true and you restore DB
// from some backup that is not the latest, and you start creating new
// backups from the new DB, they will probably fail
//
// Example: Let's say you have backups 1, 2, 3, 4, 5 and you restore 3.
// If you add new data to the DB and try creating a new backup now, the
// database will diverge from backups 4 and 5 and the new backup will fail.
// If you want to create new backup, you will first have to delete backups 4
// and 5.
Status RestoreDBFromBackup(BackupID backup_id, const std::string& db_dir,
const std::string& wal_dir);
// restore from the latest backup
Status RestoreDBFromLatestBackup(const std::string& db_dir,
const std::string& wal_dir);
// deletes old backups, keeping latest num_backups_to_keep alive
Status PurgeOldBackups(uint32_t num_backups_to_keep);
// deletes a specific backup
Status DeleteBackup(BackupID backup_id);
private:
BackupEngine* backup_engine_;
};
} // rocksdb namespace