MySQL5.7以后都基本用GTID方式复制了，相对于binlog和position号方式，在failover时候减少很多人工切换操作 GTID，global transaction identitifiers，基于全局事务的复制方式，由server_uuid:transaction_i
MySQL5.7以后都基本用GTID方式复制了，相对于binlog和position号方式，在failover时候减少很多人工切换操作
GTID，global transaction identitifiers，基于全局事务的复制方式，由server_uuid:transaction_id组成,server_uuid在数据库启动过程生成,在/data/auto.cnf中
复制过程：master事务提交时GTID，记录到binlog；然后master的binlog传送到slave的relaylog,slave读取GTID生成gtid_next系统参数;slave校验GTID是否在binlog并进一步应用事务（5.7后是存放在gtid_executed系统表，这样不用开启log_slave_updates参数，从而不用把relaylog记录再记录到binlog，减少slave压力）
下面操作下：
首先主从都配置gtid_mode、enforce_gtid_consistency参数,其中备库多加个log_slave_updates=1
[root@localhost /usr/local/mysql/data]$ cat /etc/my.cnf[mysqld]datadir=/usr/local/mysql/datalog_bin=mysql-binserver_id=1gtid_mode=onenforce_gtid_consistency=on[root@localhost /usr/local/mysql/data]$
mysql> show variables like '%gtid%';+----------------------------------+-----------+| Variable_name | Value |+----------------------------------+-----------+| binlog_gtid_simple_recovery | ON || enforce_gtid_consistency | ON || gtid_executed_compression_period | 1000 || gtid_mode | ON || gtid_next | AUTOMATIC || gtid_owned | || gtid_purged | || session_track_gtids | OFF |+----------------------------------+-----------+8 rows in set (0.00 sec) mysql>
然后将之前异步复制的配置去掉，重新配置slave中主库信息即可
mysql> show variables like '%log_slave_updates%';+-------------------+-------+| Variable_name | Value |+-------------------+-------+| log_slave_updates | ON |+-------------------+-------+1 row in set (0.00 sec) mysql> stop slave;Query OK, 0 rows affected (0.01 sec) mysql> reset slave all;Query OK, 0 rows affected (0.02 sec) mysql> change master to -> master_host='192.0.1.10', -> master_user='scott', -> master_password='tiger', -> master_port=3306, -> master_auto_position=1;Query OK, 0 rows affected, 2 warnings (0.02 sec) mysql> start slave;Query OK, 0 rows affected (0.00 sec)mysql> show slave status\G*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.0.1.10 Master_User: scott Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000004 Read_Master_Log_Pos: 573 Relay_Log_File: localhost-relay-bin.000002 Relay_Log_Pos: 786 Relay_Master_Log_File: mysql-bin.000004 Slave_IO_Running: Yes Slave_SQL_Running: Yes 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: 573 Relay_Log_Space: 997 Until_Condition: None 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: 0Master_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: 1 Master_UUID: 531fa6d1-627f-11e9-8dc7-000c297887a1 Master_Info_File: /data/master.info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: 531fa6d1-627f-11e9-8dc7-000c297887a1:1-2 Executed_Gtid_Set: 531fa6d1-627f-11e9-8dc7-000c297887a1:1-2 Auto_Position: 1 Replicate_Rewrite_DB: Channel_Name: Master_TLS_Version: 1 row in set (0.00 sec) mysql>
测试一下，ok的，主库状态可以看到
mysql> show master status;+------------------+----------+--------------+------------------+------------------------------------------+| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |+------------------+----------+--------------+------------------+------------------------------------------+| mysql-bin.000004 | 573 | | | 531fa6d1-627f-11e9-8dc7-000c297887a1:1-2 |+------------------+----------+--------------+------------------+------------------------------------------+1 row in set (0.00 sec) mysql>
将slave中log_slave_updates关掉，就能看到mysql.gtid_executed表中记录已执行gtid信息了
mysql> select * from mysql.gtid_executed;+--------------------------------------+----------------+--------------+| source_uuid | interval_start | interval_end |+--------------------------------------+----------------+--------------+| 531fa6d1-627f-11e9-8dc7-000c297887a1 | 1 | 2 || 531fa6d1-627f-11e9-8dc7-000c297887a1 | 3 | 3 |+--------------------------------------+----------------+--------------+2 rows in set (0.00 sec)
由于是基于事务的，所以就有了限制条件： create table select的方式在基于行复制的情况下会被拆分为创建表和insert数据两个事件，某些情况下这两个事件会被分配相同GTID导致后面insert数据部分被忽略而产生错误； 一个事务中既包含InnoDB表又包含MyISAM表会导致可能产生多个gtid，或者表在主从库中存储引擎不一致都会产生gtid复制异常
