1、keepaliaved 抢占式配置

master配置

[root@lb01 ~]# rpm -qc keepalived
/etc/keepalived/keepalived.conf
/etc/sysconfig/keepalived
[root@lb01 ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
    router_id lb02 #标识信息，一个名字而已；
}
vrrp_instance VI_1 {
    state MASTER    #角色是master
    interface eth0  #vip 绑定端口
    virtual_router_id 50    #让master 和backup在同一个虚拟路由里，id 号必须相同；
    priority 150            #优先级,谁的优先级高谁就是master ;
    advert_int 1            #心跳间隔时间
    authentication {
        auth_type PASS      #认证
        auth_pass 1111      #密码 
}
    virtual_ipaddress {
        10.0.0.3            #虚拟ip
    }
}

backup配置

[root@lb02 ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {     
    router_id lb02   
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 50
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
}
    virtual_ipaddress {
        10.0.0.3
    }
}

[root@lb02 ~]#

2、Keepalived非抢占式配置：

非抢占式不再有主从之分，全部都为BACKUP,并且配置文件中添加nopreempt，用来标识为非抢占式；

[root@lb01 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
    router_id lb01
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 50
    priority 150
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
}
    virtual_ipaddress {
        10.0.0.3
    }
}

[root@lb02 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf 
! Configuration File for keepalived
global_defs {     
    router_id lb02   
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 50
    priority 100
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
}
    virtual_ipaddress {
        10.0.0.3
    }
}

You have new mail in /var/spool/mail/root
[root@lb02 /etc/nginx/upstream]#

3、nginx+keepalived

实现思路：将keepalived 中的vip作为nginx负载均衡的监听地址，并且域名绑定的也是vip的地址。

说明：Nginx 负载均衡实现高可用，需要借助Keepalived地址漂移功能。

在不考虑后端数据库和存储的时候如下架构

image

两台负载均衡配置：

[root@lb01 /etc/nginx/upstream]# ip add show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:97:e1:ff brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.5/24 brd 10.0.0.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet 10.0.0.3/32 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe97:e1ff/64 scope link 
       valid_lft forever preferred_lft forever
[root@lb01 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
    router_id lb01
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 50
    priority 150
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
}
    virtual_ipaddress {
        10.0.0.3
    }
}

[root@lb01 /etc/nginx/upstream]#

[root@lb02 /etc/nginx/upstream]# ip add show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:6f:18:48 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.6/24 brd 10.0.0.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe6f:1848/64 scope link 
       valid_lft forever preferred_lft forever
[root@lb02 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf 
! Configuration File for keepalived
global_defs {     
    router_id lb02   
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 50
    priority 100
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
}
    virtual_ipaddress {
        10.0.0.3
    }
}

[root@lb02 /etc/nginx/upstream]#

4、keepalived脑裂现象

由于某些原因，导致两台keepalived高可用服务器在指定时间内，无法检测到对方存活心跳信息，从而导致互相抢占对方的资源和服务所有权，然而此时两台高可用服务器有都还存活。
可能出现的原因：
1、服务器网线松动等网络故障；
2、服务器硬件故障发生损坏现象而崩溃；
3、主备都开启了firewalld 防火墙。
4、在Keepalived+nginx 架构中，当Nginx宕机，会导致用户请求失败，但是keepalived不会进行切换，
所以需要编写一个检测nginx的存活状态的脚本，如果nginx不存活，则kill掉宕掉的nginx主机上面的keepalived。(所有的keepalived都要配置)

架构如下：