keepalived+nginx部署(单主模型)

环境准备
Centos7系统，后端服务器提供web服务。
地址规划：

VS1: 172.18.51.7
VS2:172.17.51.77
RS1:172.18.51.74
RS2:172.18.51.75
VirtualIP:172.18.51.82

拓扑图：

keepalived+nginx部署(单主模型)

原理：nginx是高度模块化的应用程序，其中nginx_proxy模块即可实现负载均衡，将前端的用户请求通过调度算法分摊在后端的真实主机，达到均衡的效果。这里使用upstream模块将前端请求转发至后端；利用keepalived配置主备服务器，对各RS的健康状态进行检测，通过共用的虚拟IP地址对外提供服务。

RS：

提供httpd服务，定义web主页,并启动服务

RS的预配置脚本:

vim setparam.sh
#!/bin/bash
        #
        vip=172.18.51.100
        mask='255.255.255.255'

        case $1 in
        start)
          echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore
          echo 1 > /proc/sys/net/ipv4/conf/lo/arp_ignore
          echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce
          echo 2 > /proc/sys/net/ipv4/conf/lo/arp_announce

          ifconfig lo:0 $vip netmask $mask broadcast $vip up
          route add -host $vip dev lo:0
          ;;
        
         stop)
          ifconfig lo:0 down
          echo 0 > /proc/sys/net/ipv4/conf/all/arp_ignore
          echo 0 > /proc/sys/net/ipv4/conf/lo/arp_ignore
          echo 0 > /proc/sys/net/ipv4/conf/all/arp_announce
          echo 0 > /proc/sys/net/ipv4/conf/lo/arp_announce
          ;;
       
         *) 
          echo "Usage $(basename $0) start|stop"
          exit 1
      ;;
esac

VS：

当所有real server宕掉时，sorry server顶替，定义其主页，启动服务（注意修改服务端口为8080）

开启nginx的upstream模块，配置反向代理，启动服务（nginx占用80端口）

/etc/nginx/nginx.conf

    upstream websers {
        server 172.18.51.74:80;
        server 172.18.51.75:80;
        server 127.0.0.1:8080 backup; #设置其应急响应服务器

/etc/nginx/conf.d/default.conf

    location / {
        root   /usr/share/nginx/html;
        proxy_pass http://websers;    #代理至后端主机
        index  index.html index.htm;
    }

配置keepalived配置文件：

vs1和vs2的配置文件，主备模式、优先级不一样，其它地方一致；

/etc/keepalived/keepalived.con

! Configuration File for keepalived

global_defs {
   notification_email {       
   root@localhost
}
   notification_email_from keepalived@localhost
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   vrrp_mcast_group4 224.0.101.24
}
vrrp_script chk_down {       #存在文件时，检测成功，即执行降级；否则不存在,全部退出；实现服务器切换
        script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"
        interval 1
        weight -5
}

vrrp_script ngxstatus {    #脚本，健康状态检测，检测nginx是否存活
        script "killall -0 nginx && exit 0 || exit 1"
        interval 1
        weight -5
}

vrrp_instance sr1 {
    state MASTER
    interface ens33
    virtual_router_id 51
    priority 100
    advert_int 1
    #nopreempt            #非抢占模式（默认抢占模式）
    authentication {
        auth_type PASS
        auth_pass rE+szbuO
    }
        track_script {     #脚本调用
        chk_down
        ngxstatus
}

    virtual_ipaddress {
        172.18.51.82/16 dev ens33 label ens33:0
    }
        notify_master "/etc/keepalived/notify.sh master"
        notify_backup "/etc/keepalived/notify.sh backup"
        notify_fault "/etc/keepalived/notify.sh fault"
         #此处调用脚本实现发邮件给管理员
}

调用脚本

[root@centos703 keepalived]# vim notify.sh 
          #!/bin/bash
          #
          contact='root@localhost'
          notify() {
             mailsubject="vrrp:$(hostname) to be $1"
             mailbody="$(hostname) to be $1,vrrp transition, $(date)."
             echo "$mailbody" | mail -s "$mailsubject" $contact
          }
            case $1 in
            master)
              notify master
              ;;
            backup)
              notify backup
              ;;
            fault)
              notify fault
              ;;
            *)
              echo "Usage: $(basename $0) {master|backup|fault}"
              exit 1
              ;;
          esac
~

客户端测试：

模拟服务器正常，一台web服务器宕机，两台都宕机访问情况：

keepalived+nginx部署(单主模型)