1、Keepalived高可用的工作原理

工作原理：在Keepalived服务正常工作时，主Master节点会不断地向备节点发送（多播的方式）心跳消息，用以告诉备Backup节点自己还活着，当主Master节点发生故障时，就无法发送心跳消息，备节点也就因此无法继续检查到来自主Master节点的心跳了，于是调用自身的接管程序，接管主Master节点的IP资源及服务。而当主Master节点恢复时，备Backup节点又会释放主节点故障时自身接管的IP资源及服务，恢复到原来的备用角色。

2、Keepalived的安装

yum -y install keepalived

配置文件:/etc/keepalived/keepalived.conf

3、配置Keepalived实现单IP自动漂移接管

3.1、实例环境

lb01：10.3.151.183（主配置）
lb02：10.3.151.184（备配置）
VIP： 10.3.151.228 （虚拟IP）

3.2、主配置如下

! Configuration File for keepalived

global_defs {
   notification_email {
   [email protected]
}
   notification_email_from [email protected]
   smtp_server 192.168.200.1
   smtp_connect_timeout 30
   router_id lb01       #id为lb01，不同的keepalived.conf此ID要唯一
}

vrrp_instance VI_1 {           #实例名字为VI_1,相同实例的备节点名字要和这个相同
    state MASTER                #主状态为MASTER(必须大写)，备节点为BACKUP
    interface eth2                  #通信接口网卡
    virtual_router_id 51         #实例ID为51，keepalived.conf里唯一
    priority 150                      #优先级为150，数值越大，优先级越高，与BACKUP对比
    advert_int 1                     #通信检查间隔为1秒
    authentication {
        auth_type PASS         #PASS认证类型
        auth_pass 2222          #密码为2222
    }
    virtual_ipaddress {
        10.3.151.228/24 dev eth2 label eth2:1     #虚拟IP地址
    }
}

3.3、备节点配置文件

! Configuration File for keepalived

global_defs {
   notification_email {
   [email protected]
}
   notification_email_from [email protected]
   smtp_server 192.168.200.1
   smtp_connect_timeout 30
   router_id lb02
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth2
    virtual_router_id 51
    priority 140
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 2222
    }
    virtual_ipaddress {
        10.3.151.228/24 dev eth2 label eth2:1
    }
}

4、检查keepalived是否生效

[root@yewu-app1 nginx]# ifconfig | grep "inet addr"
          inet addr:10.3.151.183  Bcast:10.3.151.255  Mask:255.255.255.0
          inet addr:10.3.151.228  Bcast:0.0.0.0  Mask:255.255.255.0   
                    #在主节点，检查VIP是否生效
          inet addr:127.0.0.1  Mask:255.0.0.0
[root@yewu-app1 nginx]# /etc/init.d/keepalived stop      #停止主节点的keepalived
Stopping keepalived: [  OK  ]
[root@yewu-app1 nginx]# ifconfig | grep "inet addr"        #VIP已飘走
          inet addr:10.3.151.183  Bcast:10.3.151.255  Mask:255.255.255.0
          inet addr:127.0.0.1  Mask:255.0.0.0
[root@yewu-app2 nginx]# ifconfig | grep "inet addr"       #在备节点上查看VIP是否存在
          inet addr:10.3.151.184  Bcast:10.3.151.255  Mask:255.255.255.0
          inet addr:10.3.151.228  Bcast:0.0.0.0  Mask:255.255.255.0
          inet addr:127.0.0.1  Mask:255.0.0.0