高可用的LVS(DR模式)—(HA+LB)
Keepalived:
什么是Keepalived呢,keepalived观其名可知,保持存活,在网络里面就是保持在线了,也就是所谓的高可用或热备,用来防止单点故障(单点故障是指一旦某一点出现故障就会导致整个系统架构的不可用)的发生,那说到keepalived时不得不说的一个协议就是VRRP协议,可以说这个协议就是keepalived实现的基础。
VRRP( Virtual Router Redundancy Protocol )协议:
网络在设计的时候必须考虑到冗余容灾,包括线路冗余,设备冗余等,防止网络存在单点故障,那在路由器或三层交换机处实现冗余就显得尤为重要,在网络里面有个协议就是来做这事的,这个协议就是VRRP协议,Keepalived就是巧用VRRP协议来实现高可用性(HA)的。
1.用于实现路由器冗余的协议
2.解决静态路由单点故障问题
3.通过一种竞选(election)协议来实现虚拟路由器的功能
配置高可用的负载均衡
1.虚拟服务器得到最新版本的keepalived包并解压安装
tar zxf keepalived-2.0.6.tar.gz
cd keepalived-2.0.6
#安装keepalived的依赖包:openssl-devel
yum install openssl-devel.x86_64
2.编译keepalived的源码包
./configure --prefix=/usr/local/keepalived --with-init=SYSV
make (默认makefile文件)
make install
3.制作软连接方便keepalived的管理与设置,并给他的脚本执行权限
ln -s /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
ln -s /usr/local/keepalived/etc/keepalived/ /etc/
ln -s /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
ln -s /usr/local/keepalived/sbin/keepalived /sbin/
chmod +x /usr/local/keepalived/etc/rc.d/init.d/keepalived
6.将server1中源码编译好的keepalived发送到server4,在sever4中同样制作软连接:
ln -s /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
ln -s /usr/local/keepalived/etc/keepalived/ /etc/
ln -s /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
ln -s /usr/local/keepalived/sbin/keepalived /sbin/
7.在server1(主)中配置/keepalived的配置文件:
Keepalived配置文件详解:
Keepalived的所有配置都在一个配置文件里面设置,支持的配置项主要分三类: 1. 全局配置(Global Configuration):作用于整个keepalived服务 2.VRRPD配置:keepalived的核心 3. 虚拟服务配置:指定服务与负载均衡 配置文件都是以块(block)形式组织的,每个块都在{ }包围的范围内 #和!开头的行都是注释
vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
全局配置
----
global_defs { #全局定义块
notification_email { #邮件通知
sysadmin@localhost
}
#notification_email指定keepalived在发生事件(切换),需要发送email到的对象。可以有多个,每行一个。
notification_email_from keepalive@localhost
smtp_server 127.0.0.1 #smtp_*指定发送email的smtp服务器
smtp_connect_timeout 30
router_id LVS_DEVEL #router_id运行keepalived的机器的一个标识
vrrp_skip_check_adv_addr
#vrrp_strict
vrrp_garp_interval 0
vrrp_gna_interval 0
}
VRRPD配置
-------
vrrp_instance VI_1 {
##state指定instance的初始化状态,在两台router都启动后,马上会发生竞选,高priority的会竞选为Master,因而这里的state并不表示这台就一直是Master
state MASTER # 指定该节点为主节点,备用节点设置为BACKUP
interface eth0 #绑定虚拟IP的网络接口
virtual_router_id 1 #设置验证信息,两个节点需一致
priority 100 # 主节点的优先级,数值在1~254,注意从节点必须比主节点的优先级别低
advert_int 1 #组播信息发送间隔,两个节点需一致
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
172.25.1.100 #指定虚拟IP,两个节点需设置一样
}
}
虚拟服务配置
------
virtual_server 172.25.1.100 80 {
delay_loop 3 #指定检查间隔
lb_algo rr #指定lvs算法
lb_kind DR #指定lvs模式为DR
#persistence_timeout 50 #持久连接设置,会话保持时间,在此处需要注释
protocol TCP #指定转发协议为TCP协议
#后端实际TCP服务配置
real_server 172.25.1.2 80 {
weight 1
TCP_CHECK {
connect_timeout 3
retry 3
delay_before_retry 3
}
}
real_server 172.25.1.3 80 {
weight 1
TCP_CHECK {
connect_timeout 3
retry 3
delay_before_retry 3
}
}
}
4.开启keepzlived
/etc/init.d/keepalived start
5.查看日志,判定是否更新了MASTER和BACKUP
server1:
server4:
6.将配置好的keepalived文件发送给备机(server4),修改MASTER为BACKUP
scp -r /etc/keepalived root@172.25.1.4:/etc
4.删除server1和server4上子网掩码为24的ip172.25.1.100(虚拟服务器的vip)
ip addr del 172.25.1.100/24 dev eth0
5.在测试端curl 172.25.1.100
破坏server1 echo c > /proc/sysrq-trigger查看server1和server4的日志:我们可以清楚的看到,server4变为MASTER,继续提供服务,测试端不会停止。当server1恢复正常后,server1立即竞选变为MASTER,servere4恢复为BACKUP