keepalived+lvs实现对mysql读负载均衡
环境：redhat 6.5
real server: 172.25.254.189 172.25.254.224
lvs: 172.25.254.5 172.25.254.112
给real server端配置VIP，写脚本
#!/bin/bash
VIP=172.25.254.222
. /etc/init.d/functions
case "$1" in
start)
/sbin/ifconfig lo:0 $VIP broadcast netmask 255.255.255.255 up
echo "real server lvs start"
echo "1" > /proc/sys/net/ipv4/conf/lo/arp_ignore
echo "2" > /proc/sys/net/ipv4/conf/lo/arp_announce
echo "1" > /proc/sys/net/ipv4/conf/all/arp_ignore
echo "2" > /proc/sys/net/ipv4/conf/all/arp_announce
;;
stop)
/sbin/ifconfig lo:0 down
echo "real server lvs stop"
echo "0" > /proc/sys/net/ipv4/conf/lo/arp_ignore
echo "0" > /proc/sys/net/ipv4/conf/lo/arp_announce
echo "0" > /proc/sys/net/ipv4/conf/all/arp_ignore
echo "0" > /proc/sys/net/ipv4/conf/all/arp_announce
;;
*)
echo "Usage: $0 (start|stop)"
exit 1
esac
exit 0
配置lvs和keepalived
安装ipvsadm
yum install ipvsadm -y
在两台调度端上安装keepalived
tar zxf keepalived-1.2.19.tar.gz
yum install -y libnl-devel openssl-devel gcc
./configure --prefix=/usr/local/keepalived
make
make install
scp -r /usr/local/keepalived/ 172.25.7.4:/usr/local/
两台lvs上配置
ln -s /usr/local/keepalived/etc/keepalived/ /etc/ ##配置文件
ln -s /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
ln -s /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/ ##启动脚本
ln -s /usr/local/keepalived/sbin/keepalived /sbin/
对keepalived的配置
vim /etc/keepalived/keepalived.conf
vrrp_instance VI_1 { ##vrrp虚拟路由协议
14 state MASTER ##备机改为BACKUP，此状态是由priority的值来决定的，当前的优先级值小于备机的值，则将会失去MASTER状态
15 interface eth0 ##HA监测网络接口，用于心跳信息的传递
16 virtual_router_id 7 ##主备机的虚拟路由id必须相同，取值0-255
17 priority 100 ##主机的优先级，备份机改为90，主机优先级一定大于
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
172.25.254.222
}
}
virtual_server 172.25.254.222 3306 {
delay_loop 3
lb_algo rr
lb_kind DR
# nat_mask 255.255.255.0
# persistence_timeout 50
protocol TCP
real_server 172.25.254.189 3306{
weight 1
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
real_server 172.25.254.224 3306{
weight 1
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
对两台real server的mysql做主从复制，然后开启服务，具体的主从复制步骤可以查看mysql的笔记
sh /etc/lvs.sh start
/etc/init.d/mysqld start
调度端
[root@server5 mail]# /etc/init.d/keepalived restart
Stopping keepalived: [ OK ]
Starting keepalived: [ OK ]
[root@server5 mail]# ipvsadm -L
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 172.25.254.111:http rr
-> localhost:http Local 1 0 0
TCP 172.25.254.222:mysql rr
-> sky.example.com:mysql Route 1 0 0
-> server0.example.com:mysql Route 1 0 0
常见问题
1）为什么同一个IP的某一个时间段访问的都分配到同一个real server.
LVS的持久链接有两种，持久时间工作原理
当一个新的请求进来的时候，就创建了一个此IP的信息，并添加一个state为none的记录，该记录有效期会轮询至此ip端的链接信息的超时退出DIRCTOR。
2） RealServer 为什么要在 lo 接口上配置 VIP,在出口网卡上配置 VIP 可以吗?
既然要让 RS 能够处理目标地址为 vip 的 IP 包,首先必须要让 RS 能接收到这个包。在 lo 上配置 vip 能够完成接收包并将结果返回 client。
答案是不可以将 VIP 设置在出口网卡上,否则会响应客户端的 arp request,造成 client/gatewayarp table 紊乱,以至于整个 loadbalance 都不能正常工作
- RealServer 为什么要抑制 arp 帧?这个问题在上一问题中已经作了说明,这里结合实施命令进一步阐述。我们在具体实施部署的时候都会作如下调整:
echo "1" >/proc/sys/net/ipv4/conf/lo/arp_ignore
echo "2">/proc/sys/net/ipv4/conf/lo/arp_announce
echo "1">/proc/sys/net/ipv4/conf/all/arp_ignore
echo "2">/proc/sys/net/ipv4/conf/all/arp_announce
4）脑裂：
如果实际生产环境中为了避免脑裂问题，需要把BACKUP和MATER的优先级设置的不一样。