概述
mysql主主复制
所谓主主复制，即双主备份，或者叫互作主从复制，每台master既是master，又是slave。这种方案，既做到了访问量的压力分流，同时也解决了单点故障问题。
Keepalived
VRRP协议
VRRP可以将两台或者多台物理路由器设备虚拟成一个虚拟路由，这个虚拟路由器通过虚拟IP（一个或者多个)对外提供服务，而在虚拟路由器内部十多个物理路由器协同工作，同一时间只有一台物理路由器对外提供服务，这台物理路由设备被成为：主路由器（Master角色)，一般情况下Master是由选举算法产生，它拥有对外服务的虚拟IP，提供各种网络功能，如：ARP请求，ICMP 数据转发等，而且其它的物理路由器不拥有对外的虚拟IP，也不提供对外网络功能，仅仅接收MASTER的VRRP状态通告信息，这些路由器被统称为“BACKUP的角色”，当主路由器失败时，处于BACKUP角色的备份路由器将重新进行选举，产生一个新的主路由器进入MASTER角色，继续提供对外服务，整个切换对用户来说是完全透明的。
Keepalived工作原理
Keepalived的作用是检测服务器的状态，如果有一台web服务器宕机，或工作出现故障，Keepalived将检测到，并将有故障的服务器从系统中剔除，同时使用其他服务器代替该服务器的工作，当服务器工作正常后Keepalived自动将服务器加入到服务器群中，这些工作全部自动完成，不需要人工干涉，需要人工做的只是修复故障的服务器。
服务器信息
架构图：
安装mysql
配置镜像源
配置镜像源创建文件/etc/yum.repos.d/mysql57.repo：
# Enable to use MySQL 5.7
[mysql57-community]
name=MySQL 5.7 Community Server
baseurl=http://repo.mysql.com/yum/mysql-5.7-community/el/7/$basearch/
enabled=1
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-mysql
更新缓存：
yum makecache
安装
yum -y install mysql mysql-server mysql-devel
systemctl start mysqld
systemctl enable mysqld
修改密码：
root@master-1 ~]#grep "temporary" /var/log/mysqld.log
2021-06-18T08:55:10.565308Z 1 [Note] A temporary password is generated for root@localhost: pFa)ajuqQ1J5
2021-06-18T08:55:12.785391Z 0 [Note] InnoDB: Creating shared tablespace for temporary tables
[root@master-1 ~]#mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.33
Copyright (c) 2000, 2021, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> set GLOBAL validate_password_policy=LOW;
mysql> set password for 'root'@'localhost'=password('XXX');
Query OK, 0 rows affected, 1 warning (0.00 sec)
创建相关目录：
mkdir /var/log/mysql
chown -R mysql.mysql /var/log/mysql
mkdir -p /data/mysql
cp -fr /var/lib/mysql/* /data/mysql/
chown -R mysql.mysql /data/mysql/
修改配置文件/etc/my.cnf：
[client] port = 3306
socket = /tmp/mysql.sock
default-character-set=utf8
[mysql]
default-character-set=utf8
[mysqld]
log-bin = mysql-bin
binlog_format = ROW
log_slave_updates = 1
expire_logs_days = 7
max_binlog_size = 100M
server-id = 1
log_timestamps = SYSTEM
log_error=/var/log/mysql/mysql.err
character-set-server=utf8
port = 3306
socket = /tmp/mysql.sock
datadir = /data/mysql/
default-storage-engine=INNODB
max_connections=200
validate_password_policy=LOW
pid-file=/var/run/mysqld/mysqld.pid
重启：
systemctl restart mysqld
配置主主
创建主从复制账号
# master-1
GRANT REPLICATION SLAVE ON *.* TO 'rep'@'192.168.10.22' identified by 'Rep@rep123';
# master-2
GRANT REPLICATION SLAVE ON *.* TO 'rep'@'192.168.10.21' identified by 'Rep@rep123';
启动主主
master-1查询master状态：
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000002 | 599 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
master-2启动主从复制：
# 启动主从复制
change master to master_host='192.168.10.21',master_user='rep',master_password='Rep@rep123',master_log_file='mysql-bin.000002',master_log_pos=599;
start slave;
# 查看slave是否正常启动
show slave status\G;
master-2查看状态：
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000002 | 599 | | | |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
master-1启动主从复制：
# 启动主从复制
change master to master_host='192.168.10.22',master_user='rep',master_password='Rep@rep123',master_log_file='mysql-bin.000002',master_log_pos=599;
start slave;
# 查看slave是否正常启动
show slave status\G;
配置keepalived
安装keepalived
master-1和master-2安装keepalived：
yum install keepalived -y
配置
master-1的/etc/keepalived/keepalived.conf：
! Configuration File for keepalived
global_defs {
router_id DB-HA
}
vrrp_script chk_mysql_port {
script "/scripts/check_mysql.sh"
interval 2
weight -5
fall 2
rise 1
}
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 110
mcast_src_ip 192.168.10.21
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.10.20
}
track_script {
chk_mysql_port
}
}
master-2的/etc/keepalived/keepalived.conf：
! Configuration File for keepalived
global_defs {
router_id DB-HA
}
vrrp_script chk_mysql_port {
script "/scripts/check_mysql.sh"
interval 2
weight -5
fall 2
rise 1
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 110
mcast_src_ip 192.168.10.22
priority 90
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.10.20
}
track_script {
chk_mysql_port
}
}
检查mysql状态的脚本/scripts/check_mysql.sh：
#!/bin/bash
counter=$(netstat -lntp|grep 3306|wc -l)
if [ "${counter}" -eq 0 ]; then
systemctl stop keepalived
fi
授权：
chmod +x /scripts/check_mysql.sh
两台主机都启动keepalived：
systemctl start keepalived
此时，可以通过ip a查看vip在192.168.10.21的网卡上：
[root@master-1 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
link/ether bc:95:e1:s9:2G:3g brd ff:ff:ff:ff:ff:ff
inet 192.168.10.12/21 brd 192.168.10.255 scope global eth0
valid_lft forever preferred_lft forever
inet 192.168.10.20/32 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::9714:an6b:43g3:c3i5/64 scope link
valid_lft forever preferred_lft forever