现阶段项目开发往往采用前后台分离，前台常用的技术有vue、react等，前台代码部署在nginx中，代码中配置了后台服务的网关地址，由网关向后台分发服务请求，架构示意图如下：
在上述架构图中，如果Nginx服务器宕机，那么客户端则无法访问后台服务，本文重点阐述基于Keepalived实现前台服务高可用。改进后架构示意图如下：
实现基于Keepalived的前台服务高可用，步骤如下：
环境说明：系统版本：centos7 ；Nginx版本：nginx-1.20.2.tar.gz；keepalived版本：keepalived-2.0.20.tar.gz；后台2个虚拟机，ip分别是：192.168.136.129、192.168.136.130
1、Nginx安装【129、130】
# 安装四个依赖
yum -y install gcc zlib zlib-devel pcre-devel openssl openssl-devel# 解压nginx源码
cd /usr/software/
tar xzvf nginx-1.20.2.tar.gz# 创建安装的文件夹
cd /usr/install
mkdir nginx-1.20.2#指定安装位置
cd /usr/software/nginx-1.20.2
./configure --prefix=/usr/install/nginx-1.20.2#编译&安装
make && make install
2、为了方便观察ip信息，修改nginx的主页面index.html
vim /usr/install/nginx-1.20.2/html/index.html【129】文件修改内容如下：
【130】文件修改内容如下：
3、【129、130】分别启动nginx
cd /usr/install/nginx-1.20.2/sbin/
./nginx4、【129、130】安装keepalived
#解压缩keepalived
cd /usr/software/
tar xzvf keepalived-2.0.20.tar.gz#创建keepalived的安装目录
cd /usr/install
mkdir keepalived-2.0.20#配置keepalived的安装目录并编译安装
cd /usr/software/keepalived-2.0.20
./configure --prefix=/usr/install/keepalived-2.0.20
make && make install5、 【129、130】etc创建keepalived配置目录，拷贝配置文件到etc目录下，并修改此文件
mkdir /etc/keepalived
cp -p /usr/install/keepalived-2.0.20/etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf
vim /etc/keepalived/keepalived.conf【129】keepalived.conf 文件信息如下：
! Configuration File for keepalivedglobal_defs {notification_email {acassen@firewall.locfailover@firewall.locsysadmin@firewall.loc}notification_email_from Alexandre.Cassen@firewall.locsmtp_server 192.168.200.1smtp_connect_timeout 30router_id LVS_DEVELvrrp_skip_check_adv_addrvrrp_garp_interval 0vrrp_gna_interval 0
}vrrp_instance VI_1 {state MASTERinterface ens33virtual_router_id 51priority 100advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {192.168.136.250}
}virtual_server 192.168.136.250 80 {delay_loop 6lb_algo rrlb_kind NATpersistence_timeout 50protocol TCPsorry_server 192.168.136.200 80real_server 192.168.136.129 80 {weight 1TCP_CHECK {connect_port 80connect_timeout 3nb_get_retry 3delay_before_retry 3}}real_server 192.168.136.130 80 {weight 1TCP_CHECK {connect_port 80connect_timeout 3nb_get_retry 3delay_before_retry 3}}
}【130】keepalived.conf 文件信息如下：
! Configuration File for keepalivedglobal_defs {notification_email {acassen@firewall.locfailover@firewall.locsysadmin@firewall.loc}notification_email_from Alexandre.Cassen@firewall.locsmtp_server 192.168.200.1smtp_connect_timeout 30router_id LVS_DEVELvrrp_skip_check_adv_addrvrrp_garp_interval 0vrrp_gna_interval 0
}vrrp_instance VI_1 {state BACKUPinterface ens33virtual_router_id 51priority 80advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {192.168.136.250}
}virtual_server 192.168.136.250 80 {delay_loop 6lb_algo rrlb_kind NATpersistence_timeout 50protocol TCPsorry_server 192.168.136.200 80real_server 192.168.136.129 80 {weight 1TCP_CHECK {connect_port 80connect_timeout 3nb_get_retry 3delay_before_retry 3}}real_server 192.168.136.130 80 {weight 1TCP_CHECK {connect_port 80connect_timeout 3nb_get_retry 3delay_before_retry 3}}
}重点配置如下：
【129】state MASTER；【130】state BACKUP；
interface ens33 ：网卡名称
virtual_ipaddress 192.168.136.250：虚拟地址，就是客户端可以访问的地址
【129】priority 100；【130】priority 80；【129】的优先级高
real_server 192.168.136.129 80 真实的nginx地址
real_server 192.168.136.130 80 真实的nginx地址
6、【129】、【130】分别启动keepalived并测试
cd /etc/keepalived
service keepalived start
service keepalived status浏览器输入虚地址：http://192.168.136.250/ ，由于129是master，显示129的ip地址
当129虚拟机宕机时（模拟关闭电源），再次访问 http://192.168.136.250/是，显示130的ip地址，实现了前台服务的高可用。
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