一、gtid特性介绍：
GTID(global transaction identifier)是MySQL 5.6的新特性，可以唯一的标识一个事务，由UUID+TID组成：
- UUID是MySQL实例的唯一标识
- TID是该实例上已提交的事务的数量
在主从复制中，GTID代替了classic的复制方法，不再使用binlog+pos开启复制，而是使用master_auto_postion = 1的方式自动匹配GTID断点进行复制。
要开启GTID，只需在MySQL参数文件中添加以下参数：
- gtid-mode = ON
- enforce_gtid_consistency = 1
二、数据恢复需求：
需要将MySQL(以下简称A库)恢复到一天前的凌晨12:00左右的状态 需要具备的前提条件如下：
- 开启GTID
- 有A库昨天凌晨12:00前的xtra备份文件
- 开启binlog日志(废话)
三、恢复操作：
在另一台MySQL(B库)上进行数据的恢复，这样可以避免影响线上业务
1. 将B库data目录移走，拷贝A库备份文件到B库
- mv data data_20160716 #移走B库data
- mv A_back_20160714 data #移入A库备份文件
- chown -R mysql12300.mysql data/
2. 开启B库，配置主从
查看data目录下xtrabackup_binlog_info文件中记录的GTID：
- [root@service-test1 data]$ cat xtrabackup_binlog_info
- mysql-bin.000012 46455554 8133046e-4282-11e6-848e-026ca51d284c:1-4920155
在B库(slave)设置@@global.gtid_purged跳过备份包含的GTID，并执行change master to指定A库为主库：
- mysql> SET GLOBAL gtid_purged="8133046e-4282-11e6-848e-026ca51d284c:1-4920155";
- Query OK, 0 rows affected (0.00 sec)
- mysql> change master to Master_Host ='10.11.21.14',Master_Port=3306,Master_User='replica',Master_Password='XXXXXXXXX',MASTER_AUTO_POSITION=1;
- Query OK, 0 rows affected, 2 warnings (0.01 sec)
注意： xtrabackup_binlog_info中的GTID有时不止一个，设置@@global.gtid_purged时指定多个即可，以逗号隔开。
四、在A库binlog中找到恢复点并进行恢复
需要特别注意的是，在上述操作后，不要直接start slave，否则B库也又会跑到当前A库的状态
将A库binlog转换为sql语句：
- mysqlbinlog -vv mysql-bin.000011 > mysql-bin.000011.sql
找到前一天凌晨12:00左右的位置并记录GTID：
- # at 561467475
- #160521 0:24:31 server id 212177500 end_log_pos 561467523 CRC32 0x216072ca GTID [commit=yes]
- SET @@SESSION.GTID_NEXT= '542ef021-9a64-11e5-bc49-025d3d22c211:1348360'/*!*/;
在B库开启slave并指定恢复到的位置：
- mysql> start slave until SQL_BEFORE_GTIDS='542ef021-9a64-11e5-bc49-025d3d22c211:1348360';
- Query OK, 0 rows affected (0.00 sec)
当执行到了指定的GTID，SQL线程便会停止，但IO线程还会继续复制：
- mysql> show slave status\G
- *************************** 1. row ***************************
- Slave_IO_State: Waiting for master to send event
- Master_Host: 10.30.21.11
- Master_User: replica
- Master_Port: 7500
- Connect_Retry: 60
- Master_Log_File: mysql-bin.000011
- Read_Master_Log_Pos: 810203081
- Relay_Log_File: relay-bin.000002
- Relay_Log_Pos: 5707357
- Relay_Master_Log_File: mysql-bin.000011
- Slave_IO_Running: Yes
- Slave_SQL_Running: No
- Replicate_Do_DB:
- Replicate_Ignore_DB:
- Replicate_Do_Table:
- Replicate_Ignore_Table:
- Replicate_Wild_Do_Table:
- Replicate_Wild_Ignore_Table:
- Last_Errno: 0
- Last_Error:
- Skip_Counter: 0
- Exec_Master_Log_Pos: 561467475
- Relay_Log_Space: 254443161
- Until_Condition: SQL_BEFORE_GTIDS
- Until_Log_File:
- Until_Log_Pos: 0
- Master_SSL_Allowed: No
- Master_SSL_CA_File:
- Master_SSL_CA_Path:
- Master_SSL_Cert:
- Master_SSL_Cipher:
- Master_SSL_Key:
- Seconds_Behind_Master: NULL
- Master_SSL_Verify_Server_Cert: No
- Last_IO_Errno: 0
- Last_IO_Error:
- Last_SQL_Errno: 0
- Last_SQL_Error:
- Replicate_Ignore_Server_Ids:
- Master_Server_Id: 21117500
- Master_UUID: 63f38fe7-9e3b-11e5-9554-02eeb2c1042f
- Master_Info_File: /data1/mysql10070/data/master.info
- SQL_Delay: 0
- SQL_Remaining_Delay: NULL
- Slave_SQL_Running_State:
- Master_Retry_Count: 86400
- Master_Bind:
- Last_IO_Error_Timestamp:
- Last_SQL_Error_Timestamp:
- Master_SSL_Crl:
- Master_SSL_Crlpath:
- Retrieved_Gtid_Set: 542ef021-9a64-11e5-bc49-025d3d22c211:1341313-1368005
- Executed_Gtid_Set: 44226252-9e38-11e5-9540-02212401d46f:1,
- 542ef021-9a64-11e5-bc49-025d3d22c211:1-1348359,
- 63f38fe7-9e3b-11e5-9554-02eeb2c1042f:1
- Auto_Position: 1
- 1 row in set (0.00 sec)
好啦，想看昨天凌晨的哪些数据呀?都在B库里啦~~~
附：常见问题
在设置@@global.gtid_purged时，可能会遇到报错：
- mysql> SET GLOBAL gtid_purged="8133046e-4282-11e6-848e-026ca51d284c:1-4920155";
- ERROR 1840 (HY000): @@GLOBAL.GTID_PURGED can only be set when @@GLOBAL.GTID_EXECUTED is empty.
这是因为这台MySQL的@@GLOBAL.GTID_EXECUTED并不是空的，执行以下reset master操作就好了：
- mysql> SET GLOBAL gtid_purged="8133046e-4282-11e6-848e-026ca51d284c:1-4920155";
- ERROR 1840 (HY000): @@GLOBAL.GTID_PURGED can only be set when @@GLOBAL.GTID_EXECUTED is empty.
- mysql> show master status;
- +------------------+----------+--------------+------------------+-------------------------------------------+
- | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
- +------------------+----------+--------------+------------------+-------------------------------------------+
- | mysql-bin.000002 | 191 | | | 3857c25c-2caa-11e6-b61b-021feddc3827:1-14 |
- +------------------+----------+--------------+------------------+-------------------------------------------+
- 1 row in set (0.00 sec)
- mysql> reset master;
- Query OK, 0 rows affected (0.01 sec)
- mysql> show master status;
- +------------------+----------+--------------+------------------+-------------------+
- | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
- +------------------+----------+--------------+------------------+-------------------+
- | mysql-bin.000001 | 151 | | | |
- +------------------+----------+--------------+------------------+-------------------+
- 1 row in set (0.00 sec)
- mysql> SET GLOBAL gtid_purged="8133046e-4282-11e6-848e-026ca51d284c:1-4920155";
- Query OK, 0 rows affected (0.00 sec)
