CENTOS利用Keepalived构建双主MySQL+双机热备
之前的博文介绍了如何配置MYSQL双主互备.见http://showerlee.blog.运维网.com/2047005/1187693
这里介绍如何配合前者实现Keepalived双机热备
系统环境：CentOS 6.3 x64
MySQL版本：mysql-5.6.10
Keepalived版本：keepalived-1.2.7
MySQL-VIP：192.168.7.253
MySQL-master1：192.168.7.201
MySQL-master2：192.168.7.249
首先关闭iptables和SELINUX
# service iptables stop
# setenforce 0
# vi /etc/sysconfig/selinux
---------------
SELINUX=disabled
---------------
注: 若线上需要开启iptables,需加一条规则使keepalived的vrrp通行
# iptables -A INPUT -p vrrp -j ACCEPT
1.在MySQL-master1：192.168.7.201服务器上keepalived安装及配置
编译安装，实际以本机kernel版本为准
# wget http://www.keepalived.org/software/keepalived-1.2.7.tar.gz
# tar zxvf keepalived-1.2.7.tar.gz
# cd keepalived-1.2.7
# ./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.32-279.el6.x86_64
# make && make install
设置keepalived开机启动脚本
# cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
# cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
# cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
# chkconfig keepalived on
新建一个配置文件，默认keepalived启动会去/etc/keepalived目录下寻找配置文件
# mkdir /etc/keepalived
# vi /etc/keepalived/keepalived.conf
------------------
global_defs {
notification_email {
lzyangel@126.com
}
##当主、备份设备发生改变时，通过邮件通知
notification_email_from lzyangel@126.com
smtp_server stmp.126.com
smtp_connect_timeout 30
router_id MySQL-ha
}
vrrp_instance VI_1{
# 在初始化状态下定义为主设备
state BACKUP
# 注意网卡接口
interface eth0
virtual_router_id 51
# 优先级，另一台改为90
priority 100
advert_int 1
# 不主动抢占资源
nopreempt
authentication {
# 认证方式，可以是PASS或AH两种认证方式
auth_type PASS
# 认证密码
auth_pass 1111
}
virtual_ipaddress {
# 虚拟IP地址，随着state的变化而增加删除
192.168.7.253
}
}
virtual_server 192.168.7.253 3306 {
# 每个2秒检查一次real_server状态
delay_loop 2
# LVS算法
lb_algo wrr
# LVS模式
lb_kind DR
# 会话保持时间
persistence_timeout 60
protocol TCP
real_server 192.168.7.201 3306 {
# 权重
weight 3
# 检测到服务down后执行的脚本
notify_down /etc/rc.d/keepalived.sh
TCP_CHECK {
# 连接超时时间
connect_timeout 10
# 重连次数
nb_get_retry 3
# 重连间隔时间
delay_before_retry 3
# 健康检查端口
connect_port 3306
}
}
}
----------------------
编写检测服务down后所要执行的脚本
# vi /etc/rc.d/keepalived.sh
-------------
#!/bin/sh
/etc/init.d/keepalived stop
-------------
# chmod +x /etc/rc.d/keepalived.sh
注：此脚本是上面配置文件notify_down选项所用到的，keepalived使用notify_down选项来检查real_server的服务状态。
当发现real_server服务故障时，便触发此脚本.
我们可以看到，脚本就一个命令:
通过pkill keepalived强制杀死keepalived进程，从而实现了MySQL故障自动转移.
另外，我们不用担心两个MySQL会同时提供数据更新操作，因为每台MySQL上的keepalived的配置里面只有本机MySQL的IP+VIP，而不是两台MySQL的IP+VIP.
以上脚本是为了在测试环境实现VIP切换功能，生产环境建议使用如下脚本
---------------------------------
#!/bin/bash
# 环境变量
PATH=/bin:/usr/bin:/sbin:/usr/sbin; export PATH
# 暂停5秒执行，防止数据库人工正常重启
sleep 5
# mysql_id(存活=1 死掉=0)
mysql_id=`ps -C mysqld --noheader |wc -l`
# 判断mysql_id若死掉，则重启mysql一次，若仍然无法启动mysql则杀掉keepaliaved进程实现VIP切换
if [ $mysql_id -eq 0 ];then
/etc/init.d/mysqld restart
sleep 5
if [ $mysql_id -eq 0 ];then
/etc/init.d/keepalived stop
fi
fi
---------------------------------
启动keepalived
# /etc/init.d/keepalived start
查看连接状态
# ps -aux | grep keepalived
返回：
---------------
root 1387 1 0 21:13 ? 00:00:00 keepalived -D
root 1390 1387 0 21:13 ? 00:00:00 keepalived -D
root 1391 1387 0 21:13 ? 00:00:00 keepalived -D
root 1976 1911 0 21:16 pts/0 00:00:00 grep keepalived
--------------------
测试
查看VIP信息
# ip addr
--------------------------
............
inet 192.168.7.201/24 brd 192.168.7.255 scope global eth0
inet 192.168.7.253/32 scope global eth0
inet6 fe80::20c:29ff:feb2:9199/64 scope link
valid_lft forever preferred_lft forever
--------------------------
注:如果出现主从在切换VIP时，主的VIP未自动关闭，从的正常开启，导致都获取到VIP，造成互相冲突的情况，可手动输入如下命令删除一方的VIP地址
# ip addr del "虚拟ip" dev eth0
但此方法只是一个临时的解决方案，当手动删除VIP后，重启keepalived服务会无法正常开启vip，需要重启服务器方能恢复。
查看vrrp通信
# tcpdump vrrp
-------------------------
.....
18:10:56.365730 IP 192.168.7.201 > vrrp.mcast.net: VRRPv2, Advertisement, vrid 52, prio 40, authtype simple, intvl 1s, length 20
18:10:57.366825 IP 192.168.7.201 > vrrp.mcast.net: VRRPv2, Advertisement, vrid 52, prio 40, authtype simple, intvl 1s, length 20
18:10:58.367914 IP 192.168.7.201 > vrrp.mcast.net: VRRPv2, Advertisement, vrid 52, prio 40, authtype simple, intvl 1s, length 20
-------------------------
注:如果主keepalived挂掉，这里的日志会切换到备keeplived的信息
找一台局域网PC，然后去ping MySQL的VIP，这时候MySQL的VIP是可以ping的通的
停止MySQL服务，看keepalived健康检查程序是否会触发我们编写的脚本,去kill掉keepalived进程
# service mysqld stop
# ps -aux | grep keepalived
无返回结果
2.在MySQL-master2：192.168.7.249服务器上keepalived安装及配置
编译安装，实际以本机kernel版本为准
# wget http://www.keepalived.org/software/keepalived-1.2.7.tar.gz
# tar zxvf keepalived-1.2.7.tar.gz
# cd keepalived-1.2.7
# ./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.32-
279.el6.x86_64
# make && make install
设置keepalived开机启动脚本
# cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
# cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
# cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
# chkconfig keepalived on
新建一个配置文件，默认keepalived启动会去/etc/keepalived目录下寻找配置文件
# mkdir /etc/keepalived
# vi /etc/keepalived/keepalived.conf
------------------
global_defs {
notification_email {
lzyangel@126.com
}
notification_email_from lzyangel@126.com
smtp_server stmp.126.com
smtp_connect_timeout 30
router_id MySQL-ha
}
vrrp_instance VI_1{
# 两台配置此处均是BACKUP
state BACKUP
# 注意网卡接口
interface eth0
virtual_router_id 51
# 优先级，另一台改为100
priority 90
advert_int 1
# 不主动抢占资源
nopreempt
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.7.253
}
}
virtual_server 192.168.7.253 3306 {
# 每个2秒检查一次real_server状态
delay_loop 2
# LVS算法
lb_algo wrr
# LVS模式
lb_kind DR
# 会话保持时间
persistence_timeout 60
protocol TCP
real_server 192.168.7.249 3306 {
weight 3
# 检测到服务down后执行的脚本
notify_down /etc/rc.d/keepalived.sh
TCP_CHECK {
# 连接超时时间
connect_timeout 10
# 重连次数
nb_get_retry 3
# 重连间隔时间
delay_before_retry 3
# 健康检查端口
connect_port 3306
}
}
}
----------------------
编写检测服务down后所要执行的脚本
# vi /etc/rc.d/keepalived.sh
-------------
#!/bin/sh
/etc/init.d/keepalived stop
-------------
# chmod +x /etc/rc.d/keepalived.sh
启动keepalived
# /etc/init.d/keepalived start
查看连接状态
# ps -aux | grep keepalived
返回：
---------------
root 1387 1 0 21:13 ? 00:00:00 keepalived -D
root 1390 1387 0 21:13 ? 00:00:00 keepalived -D
root 1391 1387 0 21:13 ? 00:00:00 keepalived -D
root 1976 1911 0 21:16 pts/0 00:00:00 grep keepalived
--------------------
至此配置完成，网站后台只需要配置MySQL-VIP：192.168.7.253虚拟地址即可
这里实际连接的master数据库，以哪台master先开mysql服务为准。
当master1：192.168.7.201 mysql端口挡掉或者服务器异常关闭，keepalived会自动跳转到master2：192.168.7.249.
因为两台数据库的数据时同步的,用户访问的是MySQL-VIP：192.168.7.253虚拟地址，所以网站数据连接会无缝透明转接到master2服务器，实现双机热备+数据同步功能。保证网站数据库的实时可用性。
注：当某一台master服务器挂掉恢复后，需同时打开MYSQL服务和keepalived服务，保证另一台服务器如果挂掉会无缝转接。
所以建议mysql与keeplived设置服务开机启动。
# chkconfig mysqld on
# chkconfig keepalived on
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