安装
两台接入服务器分别安装NginX和keepalived:
准备依赖包：
yum -y install gcc pcre-devel zlib-devel openssl-devel
下载
wget http://nginx.org/download/nginx-1.2.4.tar.gz wget http://www.keepalived.org/software/keepalived-1.2.7.tar.gz
安装NginX
tar zxvf nginx-1.2.4.tar.gzcd nginx-1.2.4./configure --with-http_stub_status_modulemake && make install
安装keepalived
tar zxvf keepalived-1.2.7.tar.gzcd keepalived-1.2.7./configuremake make installcp /usr/local/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/mkdir /etc/keepalivedcp /usr/local/etc/keepalived/keepalived.conf /etc/keepalived/cp /usr/local/sbin/keepalived /usr/sbin/
加入启动服务
echo "/usr/local/nginx/sbin/nginx" >> /etc/rc.local
echo "/etc/init.d/keepalived start" >> /etc/rc.local
3 配置
3.1 配置NginX
两台接入服务器的NginX的配置完全一样,主要是配置/usr/local/nginx/conf/nginx.conf的http。其中多域名指向是通过虚拟主机（配置http下面的server）实现；同一域名的不同虚拟目录通过每个server下面的不同location实现；到后端的服务器在http下面配置upstream,然后在server或location中通过proxypass引用。要实现前面规划的接入方式，http的配置如下：
http { include mime.types; default_type application/octet-stream; sendfile on; upstream dev.hysec.com { server 50.1.1.21:80; } upstream www.hysec.com { ip_hash; server 50.1.1.10:80; server 50.1.1.11:80; server 50.1.1.12:80; } upstream oa.hysec.com { ip_hash; server 50.1.1.13:8080; server 50.1.1.14:8080; server { listen 80; server_name dev.hysec.com; location /svn { proxy_pass http://dev.hysec.com; } location /submin { proxy_pass http://dev.hysec.com; } } server { listen 80; server_name www.hysec.com; location / { proxy_pass http://www.hysec.com; } server { listen 80; server_name oa.hysec.com; location / { proxy_pass http://oa.hysec.com; }}
验证方法：
首先用IP访问前表中各个应用服务器的url
再用域名和路径访问前表中各个应用系统的域名/虚拟路径
3.2 配置keepalived
按照上面的安装方法，keepalived的配置文件在/etc/keepalived/keepalived.conf。主、从服务器的配置相关联但有所不同。如下：
Master:
! Configuration File for keepalivedglobal_defs {notification_email { wanghaikuo@hysec.com wanghaikuo@gmail.com } notification_email_from wanghaikuo@hysec.com smtp_server smtp.hysec.com smtp_connect_timeout 30 router_id nginx_master}vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 51 priority 101 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 50.1.1.2 }}
Backup:
! Configuration File for keepalivedglobal_defs {notification_email { wanghaikuo@hysec.com wanghaikuo@gmail.com } notification_email_from wanghaikuo@hysec.com smtp_server smtp.hysec.com smtp_connect_timeout 30 router_id nginx_backup}vrrp_instance VI_1 { state BACKUP interface eth0 virtual_router_id 51 priority 99 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 50.1.1.2 }}
验证：
先后在主、从服务器上启动keepalived: /etc/init.d/keepalived start
在主服务器上查看是否已经绑定了虚拟IP： ip addr
停止主服务器上的keepalived: /etc/init.d/keepalived stop 然后在从服务器上查看是否已经绑定了虚拟IP：
启动主服务器上的keepalived，看看主服务器能否重新接管虚拟IP
3.3 让keepalived监控NginX的状态
经过前面的配置，如果主服务器的keepalived停止服务，从服务器会自动接管VIP对外服务；一旦主服务器的keepalived恢复，会重新接管VIP。 但这并不是我们需要的，我们需要的是当NginX停止服务的时候能够自动切换。
keepalived支持配置监控脚本，我们可以通过脚本监控NginX的状态，如果状态不正常则进行一系列的操作，最终仍不能恢复NginX则杀掉keepalived，使得从服务器能够接管服务。
如何监控NginX的状态
最简单的做法是监控NginX进程，更靠谱的做法是检查NginX端口，最靠谱的做法是检查多个url能否获取到页面。
如何尝试恢复服务
如果发现NginX不正常，重启之。等待3秒再次校验，仍然失败则不再尝试。
根据上述策略很容易写出监控脚本。这里使用nmap检查nginx端口来判断nginx的状态，记得要首先安装nmap。监控脚本如下:
#!/bin/sh# check nginx server statusNGINX=/usr/local/nginx/sbin/nginxPORT=80nmap localhost -p $PORT | grep "$PORT/tcp open"#echo $?if [ $? -ne 0 ];then $NGINX -s stop $NGINX sleep 3 nmap localhost -p $PORT | grep "$PORT/tcp open" [ $? -ne 0 ] && /etc/init.d/keepalived stopfi
不要忘了设置脚本的执行权限，否则不起作用。
假设上述脚本放在/opt/chk_nginx.sh，则keepalived.conf中增加如下配置：
vrrp_script chk_http_port { script "/opt/chk_nginx.sh" interval 2 weight 2}track_script { chk_http_port}
更进一步，为了避免启动keepalived之前没有启动nginx , 可以在/etc/init.d/keepalived的start中首先启动nginx:
start() { /usr/local/nginx/sbin/nginx sleep 3 echo -n $"Starting $prog: " daemon keepalived ${KEEPALIVED_OPTIONS} RETVAL=$? echo [ $RETVAL -eq 0 ] && touch /var/lock/subsys/$prog}