1 规划和准备两台相同配置的web
用途
ip
MASTER
192.168.1.100
BACKUP
192.1681.101
2 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
yum-y install popt-devel
下载
wget http://nginx.org/download/nginx-1.2.4.tar.gzwget http://www.keepalived.org/software/keepalived-1.2.7.tar.gz
安装NginX
安装keepalive
tar zxvf keepalived-1.2.7.tar.gz
cd keepalived-1.2.7./configure
make
make install
cp/usr/local/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/cp/usr/local/etc/sysconfig/keepalived /etc/sysconfig/mkdir/etc/keepalived
cp/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_typeapplication/octet-stream;
sendfile on;
upstream dev.hysec.com {
server50.1.1.21:80;
}
upstream opslinux.com {
ip_hash;
server192.168.1.102:80server192.168.1.103:80server192.168.1.104:80}
server {
listen80;
server_name opslinux.com;
location/{
proxy_pass http://opslinux.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 Fileforkeepalived
global_defs {
router_id NGINX_DEVEL
}
vrrp_instance VI_1 {
state MASTERinterfaceeth0
virtual_router_id51priority101advert_int1authentication {
auth_type PASS
auth_pass1111}
virtual_ipaddress {192.168.1.100}
}
Backup:! Configuration Fileforkeepalived
global_defs {
router_id NGINX_DEVEL
}
vrrp_instance VI_1 {
state BACKUPinterfaceeth0
virtual_router_id51priority99advert_int1authentication {
auth_type PASS
auth_pass1111}
virtual_ipaddress {192.168.1.100}
}
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/bash
# check nginx server status
NGINX=/usr/local/nginx/sbin/nginx
PORT=8080nmap localhost-p $PORT | grep"$PORT/tcp open"#echo $?if[ $? -ne0];then
$NGINX-s stop
$NGINX
sleep3nmap localhost-p $PORT | grep"$PORT/tcp open"[ $? -ne0] && /etc/init.d/keepalived stop
fi
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：
主keepalived
vrrp_script chk_http_port {
script"/opt/chk_nginx.sh"interval1weight-2}
track_script {
chk_http_port
}
例子：! Configuration Fileforkeepalived
global_defs {
router_id NGINX_UPSTEAM
}
vrrp_script chk_http_port {
script"/opt/chk_nginx.sh"interval1weight-2}
vrrp_instance VI_1 {
state MASTERinterfaceeth0
virtual_router_id51priority100advert_int1authentication {
auth_type PASS
auth_pass1111}
virtual_ipaddress {192.168.1.100}
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
sleep3echo-n $"Starting $prog:"daemon keepalived ${KEEPALIVED_OPTIONS}
RETVAL=$?echo
[ $RETVAL-eq0] && touch /var/lock/subsys/$prog
}
