上一篇Linux Keepalived双机热备实现了Linux Keepalived双机热备利用Nginx进行节点切换的验证。本文实现MySQL数据库的主主同步。MySQL主主同步是独立的，与Keepalived无关，因此重点说下MySQL的配置，Keepalived节点切换与之前实现是一样的。
环境
Master1：172.18.30.17 安装mysql和keepalived
Master2: 172.18.30.98 安装mysql和keepalived
VIP：172.18.30.188
一、Mysql主主同步环境部署
1、master1配置
打开/etc/my.cnf
vi /etc/my.cnf
在my.cnf文件的[mysqld]配置区域添加下面内容：
server-id = 1
log-bin = mysql-bin
sync_binlog = 1
binlog_checksum = none
binlog_format = mixed
auto-increment-increment = 2
auto-increment-offset = 1
slave-skip-errors = all
重启数据库
/usr/bin/mysql restart
或
service mariadb restart
登陆数据库
mysql -u root
数据同步授权
grant replication slave,replication client on *.* to mysql@'172.18.30.%' identified by "password";
刷新
flush privileges;
将库锁住，仅允许读，以保证数据一致性，待主主同步环境部署后再解锁（同步前记得先解锁）
flush tables with read lock;
查看log bin日志和pos值位置
show master status;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000001 | 502 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.03 sec)
2、master2配置
打开/etc/my.cnf
vi /etc/my.cnf
在my.cnf文件的[mysqld]配置区域添加下面内容：
server-id = 2
log-bin = mysql-bin
sync_binlog = 1
binlog_checksum = none
binlog_format = mixed
auto-increment-increment = 2
auto-increment-offset = 2
slave-skip-errors = all
重启数据库
/usr/bin/mysql restart
或
service mariadb restart
数据同步授权
grant replication slave,replication client on *.* to mysql@'172.18.30.%' identified by "password";
刷新
flush privileges;
将库锁住，仅允许读
flush tables with read lock;
查看log bin日志和pos值位置
show master status;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000002 | 504 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.03 sec)
3、master1同步配置
先解锁，将对方数据同步到自己的数据库中
unlock tables;
slave stop;
change master to master_host='192.18.30.98',master_user='mysql',master_password='password',master_log_file='mysql-bin.000001',master_log_pos=502;
start slave;
查看同步状态，如下出现两个“Yes”，表明同步成功
show slave status \G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 172.18.30.98
Master_User: mysql
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 504
Relay_Log_File: mysql-relay-bin.000018
Relay_Log_Pos: 279
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
.........................
Seconds_Behind_Master: 0
.........................
这样，master1就和master2实现了主从同步，即master1同步master2的数据。
4、master2同步配置
解锁
unlock tables;
slave stop;
change master to master_host='172.18.30.17',master_user='mysql',master_password='password',master_log_file='mysql-bin.000001',master_log_pos=502;
start slave;
查看同步状态，如下出现两个“Yes”，表明同步成功
show slave status \G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 172.18.30.17
Master_User: mysql
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000002
Read_Master_Log_Pos: 502
Relay_Log_File: mysql-relay-bin.000018
Relay_Log_Pos: 279
Relay_Master_Log_File: mysql-bin.000002
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
.........................
Seconds_Behind_Master: 0
.........................
这样，master2就和master1实现了主从同步，即master2也同步master1的数据。
以上表明双方已经实现了mysql主主同步。
5、验证
打开数据库，修改master1的数据，查看master2会不会变，或反之。
二、配置Keepalived
1、安装keepalived并将其配置成系统服务
参考上一篇Linux Keepalived双机热备
2、编写切换脚本
切换脚本与上一篇的nginx_check.sh类似
vim /opt/chk_mysql.sh
#!/bin/bash
counter=$(netstat -na|grep "LISTEN"|grep "3306"|wc -l)
if [ "${counter}" -eq 0 ]; then
service keepalived stop
fi
chmod 755 /opt/chk_mysql.sh
service keepalived start
3、验证
通过虚拟IP（VIP）访问数据库，然后关掉一台数据库的服务，查看数据库是否仍然正常。
4、抢占
nopreempt这个参数只能用于state为backup的情况，所以在配置的时候要把master和backup的state都设置成backup，这样才会实现keepalived的非抢占模式。
