2. Keepalived-高可用列脑

1.Keepalived高可用列脑

由于某些原因，导致两台keepalived高可用服务器在指定时间内，无法检测到对方的心跳信息，各自取得资源及服务器的所有权，而此时的两台高可用服务器又都还活着。

• ​ 服务器网线松动等网络故障
• ​ 服务器硬件古装发生损坏现象而崩溃
• ​ 主备都开启firewalld防火墙
• ​ Nginx服务器死掉等

2. backup节点操作

1.在备上编写检测脚本，检测如果能ping通主并且备节点还有vip的话测认为列脑

[root@lb02 ~]# vim /etc/keepalived/nginx_check.sh
#!/bin/bash
lb01_vip=10.0.21.117
lb01_ip=10.0.21.115
  A=`ssh $lb01_ip "ip add | grep "$lb01_vip"|wc -l"`
  if [ $A -eq 0 -a `ip add | grep "$lb01_vip"|wc -l ` -eq 1  ];then
    sleep 5
    ssh $lb01_ip "ip add | grep "$lb01_vip"|wc -l"
          if [ $? -eq 0 -a `ip add | grep "$lb01_vip"|wc -l ` -eq 1  ];then
                systemctl stop keepalived
          fi

  fi

2.修改配置文件

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

global_defs {
   notification_email {
     [e-mail]
     [e-mail]
   }
   notification_email_from [e-mail]
   smtp_server 192.168.200.1
   smtp_connect_timeout 30
   router_id 50
}
#添加关联脚本
vrrp_script check_web {
   script "/etc/keepalived/nginx_check.sh"   
   interval 2
   weight 50
}
vrrp_instance VI_1 {
    state BACKUP
    interface ens192
    virtual_router_id 51
    priority 80
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
      10.0.21.117
    }
#关联检测脚本
    track_script {
   check_web
    }
}
[root@lb02 ~]# systemctl restart keepalived

3. maskter节点操作

如果nginx宕机，会导致用户请求失败，但keepalived并不会进行切换，所以需要编写一个检测nginx的存活脚本，如果不存活则kill nginx和keepalived

1.编写脚本

[root@lb01 keepalived]# vim check_web_pid.sh 
#!/bin/bash
A=`ps -C nginx --no-header |wc -l`
if [ $A -eq 0 ];then
        systemctl restart nginx
        if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
                killall keepalived
        fi
fi

2.修改配置文件

[root@lb01 ~]# cat /etc/keepalived/keepalived.conf 
! Configuration File for keepalived

global_defs {
   notification_email {
     [e-mail]
     [e-mail]
     [e-mail]
   }
    router_id master
}
#关联检测脚本
vrrp_script check_web {
   script "/etc/keepalived/check_web_pid.sh" 
   interval 2
   weight 50
}
nginx_check.sh
vrrp_instance VI_1 {
    state MASTER
    interface ens192
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        10.0.21.117
    }
    #关联检测脚本
    track_script {
   check_web
    }
}

[root@lb01 ~]# systemctl restart keepalived

验证

1.关闭nginx服务测试nginx是否会通过keepalived脚本启动
2.更改nginx配置文件，模拟nginx无法正常启动，是否会关闭lb01 keepalived服务。从而 vip切换到db02上。