首先在搭建前分析，想用Keepalived实现MySQL高可用，那么先的对Keepalived+lvs跟MySQL主主复制有所了解。因为MySQL+Keepalived架构是在Keepalived+lvs跟MySQL主主复制的基础上实现的lvs+Keepalived跟MySQL主主复制。
我们的目标是，两台MySQL服务器如果其中有一台MySQL服务器挂掉后，另外一台能立马接替其进行工作。因此我们就必须保证两台MySQL数据库的数据完全一样，而且当挂掉的那一台重新启动的话，不再会被客户端继被访问，而是会充当备机跟现在工作的MySQL进行数据同步，一直到提供服务的那台挂掉后再接替其工作。如此周而复始的实现了MySQL的高可用。在通常情况下实现这种模式的Keepalived无疑是最好的选择。因为有虚拟IP的原因，如果有一台MySQL挂掉了，Keepalived会从服务器群中剔除，而客户端访问会被切换到另外一台接替其工作的机器上。
在搭建的时候一些注意事项，MySQL主主复制跟lvs+Keepalived搭建的注意事情前面博文已经提高这里就不再啰嗦。在搭建完毕后，因为arp的原因不能够实现自由切换。这就是要注意的重点。
vim /etc/sysctl.conf
#.............前面部分省去
#######以下是文件末尾添加的部分######
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2
net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.lo.arp_announce = 2
##这4行的主要作用是本地arp不作回应##
添加完后保存退出，并执行：sysctl -p使其生效
[root@mysql-ha1 ~]# sysctl -p
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.eth0.send_redirects = 0
net.ipv4.conf.eth0.send_redirects = 0
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2
net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.lo.arp_announce = 2
下面具体操作，首先有两台mysql机器已经搭建好了mysql的主主复制
vip:192.168.5.55
mysql-ha1:192.168.5.234
mysql-ha2:192.168.5.155
在两台mysql机器上都安装ipvsadm,keepalived，首先在mysql-ha1(192.168.5.234)安装
[root@mysql-ha1 src]# wget http://www.keepalived.org/software/keepalived-1.2.2.tar.gz
[root@mysql-ha1 src]# wget http://www.linuxvirtualserver.org/software/kernel-2.6/ipvsadm-1.26.tar.gz
[root@mysql-ha1 src]# rpm -ivh popt-static-1.13-7.el6.x86_64.rpm
[root@mysql-ha1 src]# yum -y install kernel-devel make gcc openssl-devel libnl* popt*
[root@mysql-ha1 src]# ln -s /usr/src/kernels/2.6.32-220.13.1.el6.x86_64/ /usr/src/linux
[root@mysql-ha1 src]# tar -zxvf ipvsadm-1.26.tar.gz
[root@mysql-ha1 src]# cd ipvsadm-1.26/
[root@mysql-ha1 ipvsadm-1.26]# make
[root@mysql-ha1 ipvsadm-1.26]# make install
[root@mysql-ha1 ipvsadm-1.26]# cd ..
[root@mysql-ha1 src]# tar -zxvf keepalived-1.2.2.tar.gz
[root@mysql-ha1 src]# cd keepalived-1.2.2/
[root@mysql-ha1 keepalived-1.2.2]# ./configure --with-kernel-dir=/usr/src/kernels/2.6.32-358.2.1.el6.x86_64/
[root@mysql-ha1 keepalived-1.2.2]# make && make install
[root@mysql-ha1 keepalived-1.2.2]# cp /usr/local/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
[root@mysql-ha1 keepalived-1.2.2]# cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/
[root@mysql-ha1 keepalived-1.2.2]# mkdir /etc/keepalived
[root@mysql-ha1 keepalived-1.2.2]# cp /usr/local/etc/keepalived/keepalived.conf /etc/keepalived/
[root@mysql-ha1 keepalived-1.2.2]# cp /usr/local/sbin/keepalived /usr/sbin/
在mysql-ha2（192.168.5.155）也同样进行安装
然后我们编辑keepalived配置文件，下面是mysql-ha1（192.168.5.234）上的配置文件内容
[root@mysql-ha1 ~]# >/etc/keepalived/keepalived.conf
[root@mysql-ha1 ~]# vim /etc/keepalived/keepalived.conf
#! Configuration File for keepalived
global_defs {
router_id mysql-ha1 #修改为自己的主机名
}
##################第一部分###################
vrrp_instance VI_1 {
state BACKUP #都修改成BACKUP
interface eth0
virtual_router_id 60 #默认51 主从都修改为60
priority 100 #在mysql-ha2上LVS上修改成80
advert_int 1
nopreempt #不抢占资源，意思就是它活了之后也不会再把主抢回来
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.5.55
}
}
##################第二部分###################
virtual_server 192.168.5.55 3306 {
delay_loop 6
lb_algo wrr
lb_kind DR
nat_mask 255.255.255.0
persistence_timeout 50
protocol TCP
real_server 192.168.5.234 3306 {
weight 1
notify_down /usr/local/mysql/bin/mysql.sh
TCP_CHECK {
connect_timeout 10
nb_get_retry 3
connect_port 3306
}
}
}
这里需要注意的是，notify_down /usr/local/mysql/bin/mysql.sh这个选项，这个是是在keepalived检测不到mysql的时候要执行的脚本，从上面的配置文件来看real服务器只有本机。那么，keeaplived如果启动，客户端也只是访问本机的mysql。nopreempt这个选下也得注意，这个是不抢占资源在优先级高的机器上配置就可以。
看下这个脚本的内容：
[root@mysql-ha1 ~]# vim /usr/local/mysql/bin/mysql.sh
#!/bin/bash
pkill keepalived
[root@mysql-ha1 ~]# chmod +x /usr/local/mysql/bin/mysql.sh
脚本内容就一条命令：pkill keepalived，主要作用是如果本机的mysql挂掉了，那么同时会杀死本机的keepalived，这样另外一台就会接替他工作，虚拟IP也会被另一台接管，如果不杀死keepalived虚拟IP不会被另一台接管，mysql访问也就不会切换过去。
测试下如果，mysql服务器挂掉，脚本是否可以杀死keepalived
[root@mysql-ha1 ~]# ps aux | grep keepalived
root 2518 0.0 0.0 41796 936 ? Ss 19:35 0:00 keepalived -D
root 2519 0.0 0.1 43900 2152 ? S 19:35 0:00 keepalived -D
root 2520 0.0 0.0 43900 1572 ? S 19:35 0:00 keepalived -D
root 2610 0.0 0.0 103240 860 pts/0 S+ 23:07 0:00 grep keepalived
[root@mysql-ha1 ~]# netstat -ntlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 2237/mysqld
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1041/sshd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1416/master
tcp 0 0 0.0.0.0:5672 0.0.0.0:* LISTEN 1429/qpidd
tcp 0 0 :::22 :::* LISTEN 1041/sshd
tcp 0 0 ::1:25 :::* LISTEN 1416/master
[root@mysql-ha1 ~]# service mysqld stop
Shutting down MySQL... SUCCESS!
[root@mysql-ha1 ~]# ps aux | grep keepalived
root 2640 0.0 0.0 103240 856 pts/0 S+ 23:07 0:00 grep keepalived
[root@mysql-ha1 ~]# netstat -ntlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1041/sshd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1416/master
tcp 0 0 0.0.0.0:5672 0.0.0.0:* LISTEN 1429/qpidd
tcp 0 0 :::22 :::* LISTEN 1041/sshd
tcp 0 0 ::1:25 :::* LISTEN 1416/master
[root@mysql-ha1 ~]#
可以看到当mysqld服务器挂掉后，脚本生效同时杀死本机keepalived使得mysql故障转移。这时另一台keepalived会接替它工作。
同样看下mysql-ha2(192.168.5.155)上keepalived配置文件
[root@mysql-ha2 ~]# vim /etc/keepalived/keepalived.conf
#! Configuration File for keepalived
global_defs {
router_id mysql-ha1 #修改为自己的主机名
}
##################第一部分###################
vrrp_instance VI_1 {
state BACKUP #都修改成BACKUP
interface eth1
virtual_router_id 60 #默认51 主从都修改为60
priority 80 #在mysql-ha1上LVS上修改成100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.5.55
}
}
##################第二部分###################
virtual_server 192.168.5.55 3306 {
delay_loop 6
lb_algo wrr
lb_kind DR
nat_mask 255.255.255.0
persistence_timeout 50
protocol TCP
real_server 192.168.5.155 3306 {
weight 1
notify_down /usr/local/mysql/bin/mysql.sh
TCP_CHECK {
connect_timeout 10
nb_get_retry 3
connect_port 3306
}
}
}
配置完毕后可以查看下keealived有没有检测到本机的mysql。（启动的时候先启动mysql在启动keepalived,要不mysql没起来启动keepalived会被脚本杀死。）
先看下mysql-ha1(192.168.5.234)
[root@mysql-ha1 ~]# service mysqld start
Starting MySQL.. SUCCESS!
[root@mysql-ha1 ~]# /etc/init.d/keepalived start
正在启动 keepalived：
[root@mysql-ha1 ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 192.168.5.55:mysql wrr persistent 50
-> 192.168.5.234:mysql Local 1 0 0
然后再看下mysql-ha1(192.168.5.155)
[root@mysql-ha2 ~]# service mysqld start
Starting MySQL.. SUCCESS!
[root@mysql-ha2 ~]# /etc/init.d/keepalived start
正在启动 keepalived： [确定]
[root@mysql-ha2 ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 192.168.5.55:3306 wrr persistent 50
-> 192.168.5.155:3306 Local 1 0 0
测试只开启mysql-ha1(192.168.5.234)mysql服务跟keepalived用客户端链接虚拟ip
[root@mysql-ha1 ~]# ps aux | grep keepalived
root 2977 0.0 0.0 41796 936 ? Ss 23:14 0:00 keepalived -D
root 2978 0.0 0.1 43900 2156 ? S 23:14 0:00 keepalived -D
root 2979 0.0 0.0 43900 1576 ? S 23:14 0:00 keepalived -D
root 2982 0.0 0.0 103240 860 pts/0 S+ 23:16 0:00 grep keepalived
[root@mysql-ha1 ~]# netstat -ntlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 2917/mysqld
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1041/sshd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1416/master
tcp 0 0 0.0.0.0:5672 0.0.0.0:* LISTEN 1429/qpidd
tcp 0 0 :::22 :::* LISTEN 1041/sshd
tcp 0 0 ::1:25 :::* LISTEN 1416/master
mysql-ha2(192.168.5.155)
[root@mysql-ha2 ~]# ps aux | grep keepalived
root 10576 0.0 0.0 5980 756 pts/4 S+ 15:24 0:00 grep keepalived
[root@mysql-ha2 ~]# netstat -ntlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 4776/sshd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1101/master
tcp 0 0 0.0.0.0:5672 0.0.0.0:* LISTEN 1114/qpidd
tcp 0 0 :::22 :::* LISTEN 4776/sshd
tcp 0 0 ::1:25 :::* LISTEN 1101/master
然后用客户端：192.168.5.10连接
C:\Users\Administrator>mysql -uduyunlong -p123456 -h192.168.5.55
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 33
Server version: 5.5.22-log Source distribution
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set (0.02 sec)
mysql>
然后把mysql-ha1（192.168.5.234）mysql服务关掉，开启mysql-ha2(192.168.5.155)上的mysql服务跟keepalived。然后不退出mysql，继续查看数据库：
mysql-ha1(192.168.5.234)
[root@mysql-ha1 ~]# service mysqld stop
Shutting down MySQL... SUCCESS!
mysql-ha2(192.168.5.155)
12345 [root@mysql-ha2 ~]# service mysqld start
Starting MySQL.. SUCCESS!
[root@mysql-ha2 ~]# /etc/init.d/keepalived start
正在启动 keepalived： [确定]
[root@mysql-ha2 ~]#
客户端：192.168.5.10
mysql> show databases;
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id: 4
Current database: *** NONE ***
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set (0.01 sec)
mysql>
切换很快，大概在2到3秒之间！
CentOS 6.5高可用集群LVS+Keepalived(DR模式)：http://www.linuxdiyf.com/linux/11464.html
CentOS 6.4下DNS+Squid+Nginx+MySQL搭建高可用Web服务器：http://www.linuxdiyf.com/linux/10741.html
CentOS 6.4下LVS+Keepalived的高可用（LVS/DR模式）：http://www.linuxdiyf.com/linux/10737.html
Linux系统高可用集群软件之Keepalived：http://www.linuxdiyf.com/linux/10347.html
CentOS 7下搭建高可用集群：http://www.linuxdiyf.com/linux/10435.html