一个简单的binlog恢复测试
日常的数据备份及恢复测试，是DBA工作重中之重的事情，所以要做好备份及测试，日常的备份常见有mysqldump+binlog备份、xtrabackup+binlog备份，无论那一种，几乎都少不了对binlog的备份，说明了binlog在数据恢复中的重要性，下面做个小测试，是工作中不少运维或者新人DBA容易犯的错。
创建一个测试表tb1：
<test>(root@localhost) [xuanzhi]> show create table tb1\G *************************** 1. row *************************** Table: tb1 Create Table: CREATE TABLE `tb1` ( `id` int(10) NOT NULL AUTO_INCREMENT, `name` char(10) CHARACTER SET latin1 DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 1 row in set (0.00 sec) <test>(root@localhost) [xuanzhi]>
往表里插入两条数据：
<test>(root@localhost) [xuanzhi]> insert into tb1 (name) value ('aa'),('bb'); Query OK, 2 rows affected (0.01 sec) Records: 2 Duplicates: 0 Warnings: 0 <test>(root@localhost) [xuanzhi]> show master logs; +----------------------+-----------+ | Log_name | File_size | +----------------------+-----------+ | localhost-bin.000001 | 329 | +----------------------+-----------+ 1 row in set (0.00 sec) <test>(root@localhost) [xuanzhi]>
这个时候对数据备份，如果是xtrabackup备份的话，会在有xtrabackup_binlog_info文件中记录此时备份是到那个binlog文件和pos点的，如果是mysqldump备份，则需要带上--master-data=2这个参数，下面我们的数据量少，用mysqldump备份：
[root@localhost ~]# mysqldump -uroot -p123456 -R --events --triggers=true --master-data=2 --single-transaction xuanzhi > xuanzhi.sql Warning: Using a password on the command line interface can be insecure. [root@localhost ~]# grep -i "CHANGE MASTER" xuanzhi.sql -- CHANGE MASTER TO MASTER_LOG_FILE='localhost-bin.000001', MASTER_LOG_POS=329; [root@localhost ~]#
备份完后，继续模拟数据库有写入，而还是写在localhost-bin.000001
<test>(root@localhost) [xuanzhi]> insert into tb1 (name) value ('cc'),('dd'); Query OK, 2 rows affected (0.00 sec) Records: 2 Duplicates: 0 Warnings: 0 <test>(root@localhost) [xuanzhi]> show master logs; +----------------------+-----------+ | Log_name | File_size | +----------------------+-----------+ | localhost-bin.000001 | 538 | +----------------------+-----------+ 1 row in set (0.00 sec) <test>(root@localhost) [xuanzhi]> flush logs; Query OK, 0 rows affected (0.01 sec) <test>(root@localhost) [xuanzhi]> insert into tb1 (name) value ('ee'); Query OK, 1 row affected (0.00 sec) <test>(root@localhost) [xuanzhi]> show master logs; +----------------------+-----------+ | Log_name | File_size | +----------------------+-----------+ | localhost-bin.000001 | 589 | | localhost-bin.000002 | 321 | +----------------------+-----------+ 2 rows in set (0.00 sec) <test>(root@localhost) [xuanzhi]>
上面我们进行flush logs是为了模拟现在已经有多个binlog文件了，恢复时进行多个binlog一起恢复。
进行误操，把xunazhi库drop了：
<test>(root@localhost) [xuanzhi]> drop database xuanzhi; Query OK, 1 row affected (0.02 sec) <test>(root@localhost) [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | test | +--------------------+ 4 rows in set (0.00 sec) <test>(root@localhost) [(none)]>
创建数据xuanzhi，把备份导入：
<test>(root@localhost) [(none)]> create database xuanzhi; Query OK, 1 row affected (0.00 sec)
[root@localhost ~]# mysql -uroot -p123456 xuanzhi <./xuanzhi.sql
Warning: Using a password on the command line interface can be insecure.
[root@localhost ~]#
查看数据：
<test>(root@localhost) [(none)]> use xuanzhi Database changed <test>(root@localhost) [xuanzhi]> select * from tb1; +----+------+ | id | name | +----+------+ | 1 | aa | | 2 | bb | +----+------+ 2 rows in set (0.00 sec) <test>(root@localhost) [xuanzhi]>
可以看到备份前的数据恢复了，我们现在要结合Binlog来恢复，但前提要找出误操作前的pos点，也就是drop database xuanzhi前的pos点：
[root@localhost ~]# mysqlbinlog -v --base64-output=DECODE-ROWS localhost-bin.000002 |grep -C 10 -i "drop database" ### INSERT INTO `xuanzhi`.`tb1` ### SET ### @1=5 ### @2='ee' # at 290 #170327 21:10:55 server id 1313306 end_log_pos 321 CRC32 0x825a2f99 Xid = 78 COMMIT/*!*/; # at 321 #170327 21:19:25 server id 1313306 end_log_pos 422 CRC32 0x8c139cac Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1490620765/*!*/; drop database xuanzhi /*!*/; DELIMITER ; # End of log file ROLLBACK /* added by mysqlbinlog */; /*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/; /*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/; [root@localhost ~]# mysql -uroot -p123456 xuanzhi <./xuanzhi.sql Warning: Using a password on the command line interface can be insecure. [root@localhost ~]#
从上面可以看到，误操作前的pos点是321，那我们现在通过binlog来进行数据恢复：
[root@localhost mysql-5.6]# mysqlbinlog --start-position=329 --stop-position=321 localhost-bin.000001 localhost-bin.000002 |mysql -uroot -p123456 xuanzhi Warning: Using a password on the command line interface can be insecure. [root@localhost mysql-5.6]#
--start-position是备份后记录下的pos点， --stop-position是误操前的pos点，如果批多个binlog文件，那么start-position是第一个binlog文件的pos点，stop-position是最后一个binlog的pos点，下面我们看下数据是否恢复回来了：
<test>(root@localhost) [xuanzhi]> select * from tb1; +----+------+ | id | name | +----+------+ | 1 | aa | | 2 | bb | | 3 | cc | | 4 | dd | | 5 | ee | +----+------+ 5 rows in set (0.00 sec) <test>(root@localhost) [xuanzhi]>
这里要提的是进行恢复前，要把需要恢复的binlog备份好，或者移动拷贝一份到另一个目录，因为进行数据导入时也会继续写binlog。假如你没有误操作的情况下，就是想测试一下数据的恢复，很多人的操作是导入备份，再从备份里记录的binlog文件名和pos点进行binlog恢复，发现步骤都很完美，也没报错，恢复后就是只有备份时的数据，没有备份后的数据，下面测试一下给大家看：
<test>(root@localhost) [xuanzhi]> insert into tb1 (name) value ('aa'),('bb'); Query OK, 2 rows affected (0.01 sec) Records: 2 Duplicates: 0 Warnings: 0 <test>(root@localhost) [xuanzhi]> select * from tb1; +----+------+ | id | name | +----+------+ | 1 | aa | | 2 | bb | +----+------+ 2 rows in set (0.00 sec) <test>(root@localhost) [xuanzhi]> show master logs; +----------------------+-----------+ | Log_name | File_size | +----------------------+-----------+ | localhost-bin.000001 | 329 | +----------------------+-----------+ 1 row in set (0.00 sec) <test>(root@localhost) [xuanzhi]>
进行备份操作：
[root@localhost ~]# mysqldump -uroot -p123456 -R --events --triggers=true --master-data=2 --single-transaction xuanzhi > xuanzhi.sql Warning: Using a password on the command line interface can be insecure. [root@localhost ~]# grep -i "change master" xuanzhi.sql -- CHANGE MASTER TO MASTER_LOG_FILE='localhost-bin.000001', MASTER_LOG_POS=329; [root@localhost ~]#
继续写localhost-bin.000001后进行flush logs生成新的binlog再继续写数据，这里只是想模拟localhost-bin.000001写满了切localhost-bin.000002，结合多个binlog一起恢复
<test>(root@localhost) [xuanzhi]> insert into tb1 (name) value ('cc'),('dd'); Query OK, 2 rows affected (0.00 sec) Records: 2 Duplicates: 0 Warnings: 0 <test>(root@localhost) [xuanzhi]> flush logs; Query OK, 0 rows affected (0.00 sec) <test>(root@localhost) [xuanzhi]> insert into tb1 (name) value ('dd'); Query OK, 1 row affected (0.01 sec) <test>(root@localhost) [xuanzhi]> show master logs; +----------------------+-----------+ | Log_name | File_size | +----------------------+-----------+ | localhost-bin.000001 | 589 | | localhost-bin.000002 | 321 | +----------------------+-----------+ 2 rows in set (0.00 sec) <test>(root@localhost) [xuanzhi]>
下面进行恢复测试，正常来说先把备份导入：
[root@localhost ~]# mysql -uroot -p123456 xuanzhi <./xuanzhi.sql
Warning: Using a password on the command line interface can be insecure.
[root@localhost ~]#
查看数据，只有备份的那两条记录：
<test>(root@localhost) [xuanzhi]> select * from tb1; +----+------+ | id | name | +----+------+ | 1 | aa | | 2 | bb | +----+------+ 2 rows in set (0.00 sec) <test>(root@localhost) [xuanzhi]>
那现在通过localhost-bin.000001，localhost-bin.000002来恢复后面那3条数据，那么起始pos是那个呢，就是上面备份完后备份文件里的那个pos，我们进到binlog的存放路径：
可以看到备份后的数据是没有恢复回来的。为什么呢？因为导入备份的时候，又开始写binlog了，而你恢复时用的binlog也就是现在导入备份时正在写的binlog。大体过程是这样的：
1、导入备份后，备份的所有操作都写进最后一个binlog了，也就是上面的localhost-bin.000002
2、进行binlog恢复，从备份文件里的pos点开始，按理来说是可以恢复到最新数据的，但是上面导入了备份，导入时的所有操作都会记录到localhost-bin.000002
3、备份导入时会有DROP TABLE和CREATE TABLE的动作写进binlog里，所以最终得到的数据，还是备份时的数据。
总结：
一、在恢复全备数据之前必须将该binlog文件移出，否则恢复过程中，会继续写入语句到binlog，最终导致增量恢复数据部分变得比较混乱
二、做好数据文件及binlog的备份至关重要，但不是备份完就算了，要定期进行数据恢复测试或演练
三、恢复时建议对外停止更新，即禁止更新数据库
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作者：陆炫志 出处：xuanzhi的博客 http://www.cnblogs.com/xuanzhi201111 您的支持是对博主最大的鼓励，感谢您的认真阅读。本文版权归作者所有，欢迎转载，但请保留该声明。 |
