MySQL中的xtrabackup的原理解析

xtrabackup的官方下载地址为 

http://www.percona.com/software/percona-xtrabackup。

 

xtrabackup包含两个主要的工具，即xtrabackup和innobackupex，二者区别如下：

1 xtrabackup只能备份innodb和xtradb两种引擎的表，而不能备份myisam引擎的表；

2 innobackupex是一个封装了xtrabackup的Perl脚本，支持同时备份innodb和myisam，但在对myisam备份时需要加一个全局的读锁。还有就是myisam不支持增量备份。

innobackupex工具的备份过程原理图

如图，备份开始的时候

1 首先会启动一个xtrabackup_log后台检测的进程，实时检测mysql redo的变化，一旦发现redo有新的日志写入，立刻将日志写入到日志文件xtrabackup_log中

2 复制innodb的数据文件和系统表空间文件idbdata1到对应的以默认时间戳为备份目录的地方

3 复制结束后，执行flush table with read lock操作

4 复制.frm .myd .myi文件

5 并且在这一时刻获得binary log 的位置

6 将表进行解锁unlock tables

7 停止xtrabackup_log进程

 

全库恢复的过程

这一阶段会启动xtrabackup内嵌的innodb实例，将xtrabackup日志xtrabackup_Log进行回放，将提交的事务信息变更应用到innodb数据或表空间，同时回滚未提交的事务

 

增量备份

增量备份主要是通过拷贝innodb中有变更的页(指的是LSN大于xtrabackup_checkpoints中的LSN号)。增量备份是基于全备的，第一次增量备份的数据是基于上一次全备，之后的每一次增倍都是基于上一次的增倍，最终达到一致性的增倍，增倍的过程中，和全备很类似，区别在于第二步

增量备份的恢复

和全库恢复类似，也需要两步

1 数据文件的恢复 分3部分 全备 增量备份和xtrabackup_log

2 对未提交事务的回滚

 

=================================================================================

innobackupex的使用案例

rpm -Uhv http://www.percona.com/downloads/percona-release/percona-release-0.0-1.x86_64.rpm
yum -y install percona-xtrabackup

1 创建备份用户

mysql> grant reload,lock tables,replication client on *.* to ‘dbbak‘@‘localhost‘ identified by ‘bk2016‘ ; 
mysql> flush privileges; 

进行数据库全备

mkdir -pv /data/dbbak
cd /data/dbbak

使用以下参数进行全库备份

[root@MASTER_03 dbbak]#  innobackupex --defaults-file=/etc/my.cnf --user=dbbak --password=bk2016 --socket=/data/3306/tmp/mysql.sock  /data/dbbak/

xtrabackup: Stopping log copying thread.
.160204 00:36:20 >> log scanned up to (1095197210)

160204 00:36:20 Executing UNLOCK TABLES
160204 00:36:20 All tables unlocked
160204 00:36:20 Backup created in directory ‘/data/dbbak//2016-02-04_00-35-36‘
MySQL binlog position: filename ‘mysql-bin.000011‘, position ‘1338619‘
160204 00:36:20 [00] Writing backup-my.cnf
160204 00:36:20 [00] ...done
160204 00:36:20 [00] Writing xtrabackup_info
160204 00:36:20 [00] ...done
xtrabackup: Transaction log of lsn (1095197210) to (1095197210) was copied.
160204 00:36:20 completed OK!说明备份成功

查看对应生成的文件

[root@MASTER_03 dbbak]# ll 2016-02-04_00-35-36/
total 1048648
-rw-r-----. 1 root root        387 Feb  4 00:36 backup-my.cnf
-rw-r-----. 1 root root 1073741824 Feb  4 00:35 ibdata1
drwx------. 2 root root       4096 Feb  4 00:36 iot
drwx------. 2 root root      12288 Feb  4 00:36 iot2
drwx------. 2 root root       4096 Feb  4 00:36 iot3
drwx------. 2 root root       4096 Feb  4 00:36 lsn
drwx------. 2 root root       4096 Feb  4 00:36 mysql
drwx------. 2 root root       4096 Feb  4 00:36 performance_schema
drwx------. 2 root root       4096 Feb  4 00:36 sakila
drwx------. 2 root root       4096 Feb  4 00:36 sbtest
drwx------. 2 root root       4096 Feb  4 00:36 test
drwx------. 2 root root       4096 Feb  4 00:36 xtrabackup0219
-rw-r-----. 1 root root         25 Feb  4 00:36 xtrabackup_binlog_info
-rw-r-----. 1 root root        119 Feb  4 00:36 xtrabackup_checkpoints
-rw-r-----. 1 root root        539 Feb  4 00:36 xtrabackup_info
-rw-r-----. 1 root root       2560 Feb  4 00:36 xtrabackup_logfile

需要注意的几个文件

[root@MASTER_03 dbbak]# cat 2016-02-04_00-35-36/xtrabackup_checkpoints 
backup_type = full-backuped ###全备
from_lsn = 0
to_lsn = 1095197210
last_lsn = 1095197210  #####LSN号
compact = 0
recover_binlog_info = 0
[root@MASTER_03 dbbak]# cat 2016-02-04_00-35-36/xtrabackup_binlog_info 
mysql-bin.000011    1338619

删掉某个数据库，进行全库恢复

mysql> drop database iot2;
Query OK, 49 rows affected (7.93 sec)

关闭数据库

[root@MASTER_03 dbbak]# /etc/init.d/mysqld stop
Shutting down MySQL.......... SUCCESS! 
[root@MASTER_03 dbbak]# mv /data/3306/data /data/3306/data_bak
[root@MASTER_03 dbbak]# mkdir /data/3306/data

恢复

[root@MASTER_03 dbbak]# innobackupex --apply-log /data/dbbak/2016-02-04_00-35-36/
160204 00:56:47 innobackupex: Starting the apply-log operation

IMPORTANT: Please check that the apply-log run completes successfully.
           At the end of a successful apply-log run innobackupex
           prints "completed OK!".

innobackupex version 2.3.3 based on MySQL server 5.6.24 Linux (x86_64) (revision id: 525ca7d)
xtrabackup: cd to /data/dbbak/2016-02-04_00-35-36/
xtrabackup: This target seems to be not prepared yet.
xtrabackup: xtrabackup_logfile detected: size=2097152, start_lsn=(1095197210)
xtrabackup: using the following InnoDB configuration for recovery:
xtrabackup:   innodb_data_home_dir = ./
xtrabackup:   innodb_data_file_path = ibdata1:1G:autoextend
xtrabackup:   innodb_log_group_home_dir = ./
xtrabackup:   innodb_log_files_in_group = 1
xtrabackup:   innodb_log_file_size = 2097152
xtrabackup: using the following InnoDB configuration for recovery:
xtrabackup:   innodb_data_home_dir = ./
xtrabackup:   innodb_data_file_path = ibdata1:1G:autoextend
xtrabackup:   innodb_log_group_home_dir = ./
xtrabackup:   innodb_log_files_in_group = 1
xtrabackup:   innodb_log_file_size = 2097152
xtrabackup: Starting InnoDB instance for recovery.
xtrabackup: Using 104857600 bytes for buffer pool (set by --use-memory parameter)
InnoDB: Using atomics to ref count buffer pool pages
InnoDB: The InnoDB memory heap is disabled
InnoDB: Mutexes and rw_locks use GCC atomic builtins
InnoDB: Memory barrier is not used
InnoDB: Compressed tables use zlib 1.2.3
InnoDB: Using CPU crc32 instructions
InnoDB: Initializing buffer pool, size = 100.0M
InnoDB: Completed initialization of buffer pool
InnoDB: Highest supported file format is Barracuda.
InnoDB: The log sequence numbers 532847032 and 532847032 in ibdata files do not match the log sequence number 1095197210 in the ib_logfiles!
InnoDB: Database was not shutdown normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Restoring possible half-written data pages 
InnoDB: from the doublewrite buffer...
InnoDB: 128 rollback segment(s) are active.
InnoDB: Waiting for purge to start
InnoDB: 5.6.24 started; log sequence number 1095197210
xtrabackup: Last MySQL binlog file position 1337268, file name mysql-bin.000011

xtrabackup: starting shutdown with innodb_fast_shutdown = 1
InnoDB: FTS optimize thread exiting.
InnoDB: Starting shutdown...
InnoDB: Shutdown completed; log sequence number 1095198530
xtrabackup: using the following InnoDB configuration for recovery:
xtrabackup:   innodb_data_home_dir = ./
xtrabackup:   innodb_data_file_path = ibdata1:1G:autoextend
xtrabackup:   innodb_log_group_home_dir = ./
xtrabackup:   innodb_log_files_in_group = 3
xtrabackup:   innodb_log_file_size = 1073741824
InnoDB: Using atomics to ref count buffer pool pages
InnoDB: The InnoDB memory heap is disabled
InnoDB: Mutexes and rw_locks use GCC atomic builtins
InnoDB: Memory barrier is not used
InnoDB: Compressed tables use zlib 1.2.3
InnoDB: Using CPU crc32 instructions
InnoDB: Initializing buffer pool, size = 100.0M
InnoDB: Completed initialization of buffer pool
InnoDB: Setting log file ./ib_logfile101 size to 1024 MB
InnoDB: Progress in MB: 100 200 300 400 500 600 700 800 900 1000
InnoDB: Setting log file ./ib_logfile1 size to 1024 MB
InnoDB: Progress in MB: 100 200 300 400 500 600 700 800 900 1000
InnoDB: Setting log file ./ib_logfile2 size to 1024 MB
InnoDB: Progress in MB: 100 200 300 400 500 600 700 800 900 1000
InnoDB: Renaming log file ./ib_logfile101 to ./ib_logfile0
InnoDB: New log files created, LSN=1095198530
InnoDB: Highest supported file format is Barracuda.
InnoDB: 128 rollback segment(s) are active.
InnoDB: Waiting for purge to start
InnoDB: 5.6.24 started; log sequence number 1095198732
xtrabackup: starting shutdown with innodb_fast_shutdown = 1
InnoDB: FTS optimize thread exiting.
InnoDB: Starting shutdown...
InnoDB: Shutdown completed; log sequence number 1095202631
160204 00:57:31 completed OK!

以上对应的目录就是innobackupex全备份自己创建的目录

[root@MASTER_03 dbbak]# innobackupex --defaults-file=/etc/my.cnf --copy-back --rsync /data/dbbak/2016-02-04_00-35-36/

160204 01:08:39 [01] ...done
160204 01:08:39 [01] Copying ./iot2/t_hash1#P#p3.ibd to /data/3306/data/iot2/t_hash1#P#p3.ibd
160204 01:08:39 [01] ...done
160204 01:08:39 [01] Copying ./iot2/db.opt to /data/3306/data/iot2/db.opt
160204 01:08:39 [01] ...done
160204 01:08:39 [01] Copying ./xtrabackup0219/db.opt to /data/3306/data/xtrabackup0219/db.opt
160204 01:08:39 [01] ...done
160204 01:08:39 completed OK!

 

更改权限

[root@MASTER_03 tmp]# chown -R mysql.mysql /data/3306/data/

启动mysqld

[root@MASTER_03 tmp]# /etc/init.d/mysqld start

[root@MASTER_03 tmp]# mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.28-log MySQL Community Server (GPL)

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| iot                |
| iot2               |  ###被删除的库
| iot3               |
| lsn                |
| mysql              |
| performance_schema |
| sakila             |
| sbtest             |
| test               |
| xtrabackup0219     |
+--------------------+
11 rows in set (0.00 sec)

发现数据是已经成功恢复

 

 

先全备

mysql> use xtrabackup0219;
mysql> create table t1(id int(5) primary key auto_increment,name varchar(20));

innobackupex --defaults-file=/etc/my.cnf --user=dbbak --password=bk2016 --socket=/data/3306/tmp/mysql.sock  /data/dbbak/

 

 

增量备份

#####往表里插入数据

mysql> insert into t1 select 1,‘love sql‘;
Query OK, 1 row affected (0.01 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t1 select 2,‘love sql‘;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t1 select 3,‘love sql‘;
Query OK, 1 row affected (0.01 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> select * from t1;
+----+----------+
| id | name |
+----+----------+
| 1 | love sql |
| 2 | love sql |
| 3 | love sql |
+----+----------+
3 rows in set (0.00 sec)

 

[root@MASTER_03 dbbak]# innobackupex --defaults-file=/etc/my.cnf --user=dbbak --password=bk2016 --socket=/data/3306/tmp/mysql.sock --incremental /data/dbbak/ --incremental-basedir=/data/dbbak/2016-02-04_01-44-24/ --parallel=2

[root@MASTER_03 dbbak]# du -sh *
1.5G 2016-02-04_01-44-24
6.0M 2016-02-04_01-46-48

 

[root@MASTER_03 dbbak]# cat 2016-02-04_01-46-48/xtrabackup_checkpoints 
backup_type = incremental   ###说明是增量的
from_lsn = 1095215215
to_lsn = 1095217565
last_lsn = 1095217565
compact = 0
recover_binlog_info = 0

 

此时再插入数据

mysql> insert into t1 select 4,‘mysql dba‘;
Query OK, 1 row affected (0.01 sec)
Records: 1 Duplicates: 0 Warnings: 0

增量备份2

[root@MASTER_03 dbbak]# innobackupex --defaults-file=/etc/my.cnf --user=dbbak --password=bk2016 --socket=/data/3306/tmp/mysql.sock --incremental /data/dbbak/ --incremental-basedir=/data/dbbak/2016-02-04_01-46-48/ --parallel=2

[root@MASTER_03 dbbak]# du -sh *
1.5G 2016-02-04_01-44-24
6.0M 2016-02-04_01-46-48
5.9M 2016-02-04_01-49-21

 

增量备份的恢复

增量备份的恢复需要有3个步骤

1 恢复完全备份

2 恢复增量备份到完全备份(开始恢复的增量备份要添加--redo-only参数,到最后一次增量备份要去掉--redo-only)

3 对整体的完全备份进行恢复，回滚未提交的数据

[root@MASTER_03 dbbak]# innobackupex --apply-log --redo-only /data/dbbak/2016-02-04_01-44-24/

xtrabackup: starting shutdown with innodb_fast_shutdown = 1
InnoDB: Starting shutdown...
InnoDB: Shutdown completed; log sequence number 1095209828
160204 01:27:09 completed OK!

将增量1应用到完全备份

[root@MASTER_03 dbbak]# innobackupex --apply-log --redo-only /data/dbbak/2016-02-04_01-44-24/ --incremental-dir=/data/dbbak/2016-02-04_01-46-48/

[root@MASTER_03 dbbak]# innobackupex --apply-log /data/dbbak/2016-02-04_01-44-24/ --incremental-dir=/data/dbbak/2016-02-04_01-49-21/

把所有合在一起的完全备份整体进行一次apply操作，回滚未提交的数据

[root@MASTER_03 dbbak]# innobackupex --apply-log /data/dbbak/2016-02-04_01-44-24/

 

 

模拟测试

mysql> drop table t1;
Query OK, 0 rows affected (0.05 sec)

[root@MASTER_03 dbbak]# rm -rf /data/3306/data/
[root@MASTER_03 dbbak]# mkdir /data/3306/data
[root@MASTER_03 dbbak]# innobackupex --defaults-file=/etc/my.cnf --copy-back --rsync /data/dbbak/2016-02-04_01-44-24/
[root@MASTER_03 dbbak]# chown -R mysql.mysql /data/3306/data/
登录查看

mysql> select * from t1;
+----+-----------+
| id | name |
+----+-----------+
| 1 | love sql |
| 2 | love sql |
| 3 | love sql |
| 4 | mysql dba |
+----+-----------+
4 rows in set (0.05 sec)

 

发现数据是已经正确