Linux Centos7 keepalived + nginx负载均衡

1，准备四台nginx服务器，两台做代理，两台做后端真实服务器。

2，配置两台真实服务器
第一台：

[[email?protected] ~]# systemctl start nginx
    [[email?protected] ~]# systemctl enable nginx
    [[email?protected] conf.d]# echo "server111" > /usr/share/nginx/html/index.html
    测试：
    [[email?protected] conf.d]# curl localhost
    server111

第二台：

[[email?protected] ~]# systemctl start nginx
    [[email?protected] ~]# systemctl enable nginx
    [[email?protected] conf.d]# echo "server222" > /usr/share/nginx/html/index.html
    测试：
    [[email?protected] conf.d]# curl localhost
    server222

3，配置两台nginx代理服务器

[[email?protected] ~]# systemctl start nginx
    [[email?protected] ~]# systemctl enable nginx
    [[email?protected] ~]# cd /etc/nginx/conf.d/
    [[email?protected] conf.d]# cp default.conf proxy.conf
    [[email?protected] conf.d]# mv default.conf default.conf.bak
    [[email?protected] conf.d]# vi upstream.conf
    upstream nginx_pool {
    server 10.30.161.241:80 weight=1 max_fails=2 fail_timeout=2;
    server 10.30.161.242:80 weight=1 max_fails=2 fail_timeout=2;
    }
    [[email?protected] conf.d]# vi proxy.conf 
     location / {
     proxy_pass http://nginx_pool;
     proxy_redirect default;
     proxy_set_header Host $http_host;
     proxy_set_header X-Real-IP $remote_addr;
     proxy_set_header REMOTE-HOST $remote_addr;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

将nginx的配置文件拷贝到另一台代理服务器中:

[[email?protected] conf.d]# scp proxy.conf upstream.conf 10.30.161.214:/etc/nginx/conf.d/
    分别重启nginx:
    systemctl restart nginx

4， 两台代理服务器分别安装软件

master：
    [[email?protected] conf.d]# yum install -y keepalived
    [[email?protected] conf.d]# cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
    [[email?protected] conf.d]# vim /etc/keepalived/keepalived.conf

配置keepalived，将里面内容全部删除，添加下列内容：

! Configuration File for keepalived
global_defs {
     router_id director1   #辅助改为director2
}

vrrp_instance VI_1 {
        state MASTER        #定义主还是备
        interface ens33     #VIP绑定接口
        virtual_router_id 80  #整个集群的调度器一致
        priority 100         #back改为50
        advert_int 1
        authentication {
                auth_type PASS
                auth_pass 1111
        }
        virtual_ipaddress {
                10.30.161.200/24   #设置VIP
        }
}
                backup:
                [[email?protected]_nginx ~]# cp /etc/keepalived/keepalived.conf
                [[email?protected]_nginx ~]# vi /etc/keepalived/keepalived.conf
                配置keepalived，将里面内容全部删除，添加下列内容：  
! Configuration File for keepalived

global_defs {
     router_id directory2
}

vrrp_instance VI_1 {   
        state BACKUP    
        interface ens33  
        nopreempt        
        virtual_router_id 80  
        priority 50   
        advert_int 1   
        authentication {  
                auth_type PASS
                auth_pass 1111
        }
        virtual_ipaddress {
                10.30.161.200/24
        }
}

5、两台代理服务器分别启动keepalived

[[email?protected]_nginx ~]# systemctl enable keepalived.service
    [[email?protected]_nginx ~]# systemctl start keepalived.service

6、检测是否成功

在master上 ip a  可显示VIP为10.30.161.200/24
  2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:29:a6:12 brd ff:ff:ff:ff:ff:ff
inet 10.30.161.51/24 brd 10.30.161.255 scope global dynamic ens33
   valid_lft 168379sec preferred_lft 168379sec
inet 10.30.161.200/24 scope global secondary ens33
   valid_lft forever preferred_lft forever
inet6 fe80::8cfe:8d87:6478:baee/64 scope link 
   valid_lft forever preferred_lft forever
inet6 fe80::d9c7:8228:5b45:afed/64 scope link tentative dadfailed 
   valid_lft forever preferred_lft forever

用curl访问VIP，正常轮询

[[email?protected] conf.d]# curl 10.30.161.200
server111
[[email?protected] conf.d]# curl 10.30.161.200
server222
[[email?protected] conf.d]# curl 10.30.161.200
server111
[[email?protected] conf.d]# curl 10.30.161.200
server222
 测试当一台master故障
 [[email?protected] conf.d]# systemctl stop keepalived
 ip a 发现VIP偏移到backup代理服务器上

到此：
可以解决心跳故障keepalived
但不能解决Nginx服务故障

4. 扩展对调度器Nginx健康检查（可选）两台都设置
   思路：
   让Keepalived以一定时间间隔执行一个外部脚本，脚本的功能是当Nginx失败，则关闭本机的Keepalived
   (1) script

   [[email?protected] ~]# vim /etc/keepalived/check_nginx_status.sh

   #!/bin/bash
   #+检查nginx进程是否存在
   counter=$(ps -C nginx --no-heading|wc -l) #此行有服务名
   if [ "${counter}" = "0" ]; then
   #尝试启动一次nginx，停止5秒后再次检测
   systemctl start nginx #启动服务
   sleep 5
   counter=$(ps -C nginx --no-heading|wc -l) #此行有服务名
   if [ "${counter}" = "0" ]; then
   #如果启动没成功，就杀掉keepalive触发主备切换
   service keepalived stop
   fi
   fi
   [[email?protected] ~]# chmod a+x /etc/keepalived/check_nginx_status.sh

(2). keepalived使用script

! Configuration File for keepalived

global_defs {
     router_id director1
}
vrrp_script check_nginx {     #健康检测模块调用
     script "/etc/keepalived/check_nginx_status.sh"  #指定脚本
     interval 5  #检查频率,秒
}

vrrp_instance VI_1 {
        state MASTER
        interface ens33
        virtual_router_id 80
        priority 100
        advert_int 1
        authentication {  
                auth_type PASS
                auth_pass 1111
        }
        virtual_ipaddress {
                192.168.246.16/24
        }
        track_script { 引用脚本
                check_nginx
        }
}

注：必须先启动nginx，再启动keepalived