https://blog.csdn.net/chengxuyuanyonghu/article/details/50297321
####sample 1 测试通过 (5.6 + GTID 方式同步)
1> 正常切换
1）从服务器检查SHOW PROCESSLIST语句的输出，直到你看到Has read all relaylogwaiting for the slave I/O thread to update it
从服务器：
mysql> show processlist;
+----+-------------+-----------+------+---------+------+-----------------------------------------------------------------------------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+-------------+-----------+------+---------+------+-----------------------------------------------------------------------------+------------------+
| 3 | system user | | NULL | Connect | 2316 | Waiting for master to send event | NULL |
| 4 | system user | | NULL | Connect | 2178 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL |
| 12 | root | localhost | NULL | Query | 0 | init | show processlist |
+----+-------------+-----------+------+---------+------+-----------------------------------------------------------------------------+------------------+
3 rows in set (0.00 sec)
2）确保从服务器已经处理了日志中的所有语句。
mysql> STOP SLAVE IO_THREAD
当从服务器都执行完这些，它们可以被重新配置为一个新的设置。
3）在被提升为主服务器的从服务器上，发出 STOP SLAVE和RESET MASTER和RESET SLAVE操作。
mysql> STOP SLAVE;
Query OK, 0 rows affected (0.00 sec)
mysql> RESET MASTER;
Query OK, 0 rows affected (0.01 sec)
mysql> RESET SLAVE;
Query OK, 0 rows affected (0.01 sec)
4）然后重启mysql服务。
mysqladmin -uroot -p shutdown -S /var/lib/mysql/mysql_3307.sock
mysqld_safe --defaults-file=/mysqldb/data_3307/my.cnf &
5）在备用服务器（新的主服务器）创建用户grant replication slave on *.* torepdcs@'IP of A' identified by 'replpwd'
grant allprivileges on *.* to 'repdcs'@'IP' identified by replpwd;
6) 在主服务器上RESET MASTER。然后CHANGE MASTER TOMASTER_HOST='原从服务器IP',MASTER_USER='用户名',MASTER_PASSWORD='密码' ,master_log_file='master-bin.000015' ;
mysql --host=* --port=3307 -urep -p*
change master to
master_host='*',
master_user='rep',
master_password='123456',
master_port=3307,
master_auto_position = 1;
Query OK, 0 rows affected, 2 warnings (0.02 sec)
start SLAVE;
查看状态 show slave status\G;
7)
新主库 ：
Show master status;
mysql> Show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000003 | 151 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
do some dml
mysql> Show master status;
+------------------+----------+--------------+------------------+----------------------------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+----------------------------------------+
| mysql-bin.000001 | 411 | | | a7a643b1-5a42-11e8-aa18-005056a436cc:1 |
+------------------+----------+--------------+------------------+----------------------------------------+
1 row in set (0.00 sec)
如果还不行再次重启主库，并在备库上执行CHANGE MASTER TOMASTER_HOST='192.168.0.110',MASTER_USER='repdcs',MASTER_PASSWORD='111111',master_log_file='mysqlbin.000002';
8）修改应用的连接地址到新的主库
切换完成。