1.双主复制：实现和MHA相同的效果
使用keepalive实现双主热备，防止单点故障的主从结构。
两台mysql互做主从，各自安装keepalive实现热备，其他从服务器和热备的虚拟IP建立主从连接。
2.开启两台mysql，互相建立主从
在第一台mysql创建复制用户
mysql1:
grant replication slave on *.* to repl@'192.168.8.%' identified by '123';
在第二台mysql建立和第一台的主从关系
mysql2: change master to master_host='192.168.8.10', master_user='repl', master_port=3306, master_password='123' , MASTER_AUTO_POSITION=1; start slave;
在第一台mysql再建立和第二台的主从关系
mysql1: change master to master_host='192.168.8.20', master_user='repl', master_port=3306, master_password='123' , MASTER_AUTO_POSITION=1; start slave; mysql1、mysql2: show slave status \G
3.两台服务器安装keepalived
yum -y install keepalived
4.配置mysql1的keepalived
vim /etc/keepalived/keepalived.conf
修改为：
global_defs { router_id mysql1 } vrrp_instance VI_1 { state MASTER interface ens33 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.8.254 } } virtual_server 192.168.8.254 3306 { delay_loop 6 lb_algo rr lb_kind DR persistence_timeout 50 protocol TCP real_server 192.168.8.10 3306 { weight 1 TCP_CHECK { connect_port 3306 connect_timeout 3 retry 3 delay_before_retry 3 } } }
保存退出
启动：systemctl start keepalived
5.配置mysql2的keepalived
vim /etc/keepalived/keepalived.conf
修改为：
global_defs { router_id mysql2 } vrrp_instance VI_1 { state BACKUP interface ens33 virtual_router_id 51 priority 99 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.8.254 } } virtual_server 192.168.8.254 3306 { delay_loop 6 lb_algo rr lb_kind DR persistence_timeout 50 protocol TCP real_server 192.168.8.20 3306 { weight 1 TCP_CHECK { connect_port 3306 connect_timeout 3 retry 3 delay_before_retry 3 } } } 保存退出 启动：systemctl start keepalived
6.两台服务器查看虚拟IP
ip a show dev ens33
7.开启第三台mysql,与虚拟IP建立主从
mysql3: change master to master_host='192.168.8.254', master_user='repl', master_port=3306, master_password='123' , MASTER_AUTO_POSITION=1; start slave; show slave status \G
注：其他主机ping 192.168.8.254可能会不通，第三个从服务器也无法建立主从；
keepalived切换几遍，再尝试ping。
