利用keepalived实现高可用nginx

实验拓扑图

（1）本次基于VMware Workstation搭建一个四台Linux（CentOS 7.4）系统所构成的一个服务器集群，其中两台nginx做前端调度服务器（一台为主机，另一台为备机），另外两台作为真实的Web服务器（向外部提供http服务，这里仅仅使用了CentOS默认自带的http服务，没有安装其他的类似Tomcat、Jexus服务）。

　　（2）本次实验设置了一个VIP（Virtual IP）为172.18.38.99，用户只需要访问这个IP地址即可获得网页服务。其中，nginx主机为172.18.38.100，备机为172.18.38.101。Web服务器A为172.18.38.200，Web服务器B为172.18.38.201。

一，配置nginx反向代理服务器，在两台nginx上都做一遍下面的操作

    1，在http语句块中定义调度规则
    vim /etc/nginx/nginx.conf
        http {
             .....

             upstream webser {
                        server 172.18.38.200:80;
                        server 172.18.38.201:80;
                  }

             .....
        }

    2，而后在server中调用
    vim /etc/nginx/conf.d/vhost.conf
        server {
                listen 172.18.38.99:80;
                server_name www.a.com;
                location / {
                        proxy_pass http://webser;
                }
        }

2，重启nginx，使配置生效

    systemctl restart nginx

二，配置keepalived+nginx_master服务器**

1，安装keepalived

    yum install keepalived

2，修改keepalived配置文件

 vim /etc/keepalived/keepalived.conf

    ! 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
       router_id proxy1
       vrrp_mcast_group4 224.1.1.1
    }

    vrrp_script chk_nginx {
    script "killall -0 nginx && exit 0 || exit 1"
    interval 1
    weight -30
    fall 2
    rise 2
    }
    vrrp_instance VI_1 {
        state MASTER
        interface ens37
        virtual_router_id 66
        priority 100
        advert_int 1
        authentication {
            auth_type PASS
            auth_pass 123456
        }
        virtual_ipaddress {
            172.18.38.99/16
        }
        track_script {
            chk_nginx
        }
    }

    关键配置：
        1，定义nginx健康检查脚本
        vrrp_script chk_nginx {
        script "killall -0 nginx && exit 0 || exit 1"
        interval 1     #以秒触发一次
        weight -30     #nginx宕机就立马减去有限级30
        fall 2         #检查两次如果都是宕机就表示nginx挂掉了
        rise 2         #宕机之后两次检查nginx是活着的就重新+30优先级
        }

        2，调用
        track_script {
            chk_nginx

3，启动keepalived

    systemctl  start keepalived
    systemctl enable keepalived

三，配置keepalived+nginx_slave服务器

 vim /etc/keepalived/keepalived.conf
    ! 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
       router_id proxy2
       vrrp_mcast_group4 224.1.1.1
    }

    vrrp_instance VI_1 {
        state BACKUP
        interface ens37
        virtual_router_id 66
        priority 80
        advert_int 1
        authentication {
            auth_type PASS
            auth_pass 123456
        }
        virtual_ipaddress {
            172.18.38.99/16
        }

    }

7，启动keepalived

    systemctl  start keepalived
    systemctl enable keepalived

四，配置后端web服务器

1，安装httpd软件

    1，安装httpd软件
    yum install http
    2，启动服务
        systemctl start httpd
        systemctl enable httpd
    2，生成web页面，
        A主机
            echo web_server_A > /var/www/html/index.html
        b主机
            echo web_server_B > /var/www/html/index.html

五，测试

1，不当任何服务

    [root@testsrvr ~]# for i in {1..10};do sleep 0.5;curl 172.18.38.99;done
    web_server_B
    web_server_B
    web_server_A
    web_server_A
    web_server_B
    web_server_B
    web_server_A
    web_server_A
    web_server_B
    web_server_B

2，宕一台keepalived服务

    [root@ke_nginx_S ~]# systemctl stop keepalived.service 

    [root@testsrvr  ~]# for i in {1..10};do sleep 0.5;curl 172.18.38.99;done
    web_server_B
    web_server_B
    web_server_A
    web_server_A
    web_server_B
    web_server_B
    web_server_A
    web_server_A
    web_server_B
    web_server_A

3，宕掉nginx_master服务器

    [root@ke_nginx-M ~]# systemctl stop nginx 

    [root@testsrvr ~]# for i in {1..100};do sleep 0.5;curl 172.18.38.99;done
    web_server_A
    web_server_A
    web_server_B
    web_server_B
    web_server_A
    curl: (7) couldn't connect to host
    curl: (7) couldn't connect to host
    curl: (7) couldn't connect to host
    curl: (7) couldn't connect to host
    web_server_B
    web_server_B
    web_server_A
    web_server_A