07.Nginx双机热备

• 1.Keepalived高可用概述
• 2.Keepalived高可用安装
• 3.Keepalived高可用配置
• 4.keepalived高可用列脑

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1.Keepalived高可用概述

1.什么是高可用

什么是高可用双击热备, 一般指2台机器启动着相同的业务系统,当有一台机器down机了, 另外一台服务器能快速的接管, 对于访问的用户是无感知的。

2.高可用使用场景

那么高可用使用在什么场景，业务系统需要保证7x24小时不DOWN机, 作为业务来说随时都可用, 让你的业务系统更顽强。

2.Keepalived高可用安装

1.环境准备

服务器系统	角色	外网IP	内网IP
CentOS 7.5	keepalived-master	eth0:10.0.0.5	eth1:172.16.1.5
CentOS 7.5	keepalived-slave	eth0:10.0.0.6	eth1:172.16.1.6

2.在lb01与lb02上分别安装keepalived

[root@lb01 ~]# yum install keepalived -y
[root@lb02 ~]# yum install keepalived -y

3.配置lb01, keepalived-master

[root@lb01 ~]# cat /etc/keepalived/keepalived.conf
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 {
        10.0.0.3/24 dev eth0
    }
}

4.配置lb02, keepalived-backup

[root@lb02 ~]# cat /etc/keepalived/keepalived.conf
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 {
        10.0.0.3/24 dev eth0
    }
}

5.对比keepalived的master与backup配置的区别

Keepalived配置区别	Master配置	Backup节配置
route_id(唯一标识)	route_id lb01	route_id lb02
state(角色状态)	state Master	state Backup
priority(竞选优先级)	priority 150	priority 100

6.启动lb01与lb02的keepalived

#lb01
[root@lb01 ~]# systemctl enable keepalived
[root@lb01 ~]# systemctl start keepalived

#lb02
[root@lb02 ~]# systemctl enable keepalived
[root@lb02 ~]# systemctl start keepalived

7.检查keepalived的虚拟IP地址是否漂移

在lb01上进行如下操作

# lb01存在vip地址
[root@lb01 ~]# ip addr |grep 10.0.0.3
    inet 10.0.0.3/24 scope global secondary eth0

# 停止lb01上的keepalived, 检测vip已不存在
[root@lb01 ~]# systemctl stop keepalived
[root@lb01 ~]# ip addr |grep 10.0.0.3

在lb02上进行如下操作

[root@lb02 ~]# ip addr|grep 10.0.0.3
    inet 10.0.0.3/24 scope global secondary eth0

lb01重新启动keepalived,发现地址被重新接管

[root@lb01 ~]# systemctl start keepalived
[root@lb01 ~]# ip addr |grep 10.0.0.3
    inet 10.0.0.3/24 scope global secondary eth0

3.Keepalived高可用配置

4.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消息，各自取得资源及服务的所有权，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
服务器硬件故障发生损坏现象而崩溃
主备都开启firewalld防火墙
Nginx服务死掉等

1.在备上编写检测脚本, 测试如果能ping通主并且备节点还有VIP的话则认为产生了列脑

[root@lb02 ~]# cat check_split_brain.sh
#!/bin/sh
lb01_vip=10.0.0.3
lb01_ip=10.0.0.5
while true;do
    ping -c 2 -W 3 $lb01_ip &>/dev/null
    if [ $? -eq 0 -a `ip add|grep "$lb01_vip"|wc -l` -eq 1 ];then
        echo "ha is split brain.warning."
    else
        echo "ha is ok"
    fi
sleep 5
done

2.如果Nginx宕机, 会导致用户请求失败, 但Keepalived并不会进行切换, 所以需要编写一个脚本检测Nginx的存活状态, 如果不存活则kill nginx和keepalived

[root@lb01 ~]# mkdir /server/scripts
[root@lb01 ~]# vim /server/scripts/check_web.sh
#!/bin/sh
#使用while死循环
while true;do
nginxpid=$(ps -C nginx --no-header|wc -l)
#1.判断Nginx是否存活,如果不存活则尝试启动Nginx
if [ $nginxpid -eq 0 ];then
    systemctl start nginx
    sleep 1
    #2.等待1秒后再次获取一次Nginx状态
    nginxpid=$(ps -C nginx --no-header|wc -l) 
    #3.再次进行判断, 如Nginx还不存活则停止Keepalived,让地址进行漂移,并退出脚本  
    if [ $nginxpid -eq 0 ];then
        systemctl stop keepalived
        exit 1
   fi
fi
     sleep 2
done

[root@lb01 ~]# chmod +x /server/scripts/check_web.sh

在keepalived配置文件中调用此脚本，lb01与lb02都需操作

[root@lb01 ~]# cat /etc/keepalived/keepalived.conf
global_defs {
         router_id LVS_01
}

# 每5秒执行一次脚本, 脚本执行内容不能超过5秒,否则会被中断再次重新运行脚本
vrrp_script check_web {
   script "/server/scripts/check_web.sh"
   interval 5
   weight 50
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 150
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        10.0.0.3/24 dev ens33
    }
    track_script {
        check_web
    }
}