mysql 主-主-从-从

log-bin
server-id=2/1
gtid_mode=ON
enforce_gtid_consistency=1

此时需要授权主能去从上面同步日志，由于之前在主上执行了grant replication slave on *.* to rep@‘192.168.231.%‘ identified by ‘1qaz@WSX‘;

主从同步，所以从上面也有了上面的授权信息，由于对192.168.231.% 网段授权，所以无需再授权一次了。

假如当时授权的是固定Ip，那么需要再授权一次，此时授权操作应该在主上进行，因为在从上执行不会同步到主上导致主从不一致。

mysql> change master to
    -> master_host=‘192.168.231.101‘,        #从IP
    -> master_port=3306,
    -> master_user=‘rep‘,
    -> master_password=‘1qaz@WSX‘,
    -> master_auto_position=1;                #binlog 日志位置采用自动协商方式

mysql>start slave;
mysql>show slave status\G

vi /etc/my.cnf
    server-id=3
    gtid_mode=ON
    enforce_gtid_consistency=1
    master-info-repository=TABLE                                        
    #master info 信息保存在了表里面
    relay-log-info-repository=TABLE                                # 
    #中继日志保存在表里面

分别向两个主去同步，两台机器都做如下配置
mysql> source /opt/2019-07-18-all.sql    

同步主1配置
mysql> change master to
    -> master_host=‘192.168.231.100‘,
    -> master_port=3306,
    -> master_user=‘rep‘,
    -> master_password=‘1qaz@WSX‘,
    -> master_auto_position=1 for channel ‘master1-channel‘;    #channel 名称自定义

同步主2配置
    mysql> change master to
    -> master_host=‘192.168.231.101‘,
    -> master_port=3306,
    -> master_user=‘rep‘,
    ->  master_password=‘1qaz@WSX‘,
    -> master_auto_position=1 for channel ‘master2-channel‘;    #channel 名称自定义
    -> start slave;
    -> show slave status\G

show slave status\G

报错:
    Last_IO_Error: Got fatal error 1236 from master when reading data from binary 
    log: ‘The slave is connecting using CHANGE MASTER TO 
    MASTER_AUTO_POSITION = 1, but the master has purged binary logs 
    containing GTIDs that

解决：reset master;
     stop slave;
    主上重新备份数据库，从上重新执行source /opt/2019-07-18-all.sql
    重新执行上面的change master to 等操作。