注意：
(1) 做负载均衡技术至少需要三台服务器：一台独立的负载均衡器，两台web服务器做集群
(2) keeplived（高可用）+nginx（负载均衡） 可以实现多域名对应一个VIP,并且访问不同域名，显示不同主页，可行，已测
一、nginx分别代理后端web1 和 web2的三台虚拟主机
1、web1（nginx-10.0.0.7）配置基于域名的虚拟主机（以下配置了3个虚拟主机）
[root@Oldboy extra]# cat www.conf
server {listen 80;server_name www.etiantian.org;location / {root html/www; #这个地方指向nginx安装目录的html/www/目录下index index.html index.htm;}
}
[root@Oldboy extra]# cat bbs.conf
server {listen 80;server_name bbs.etiantian.org; location / {root html/bbs;index index.php index.html index.htm;}
}
[root@Oldboy extra]# cat blog.conf
server {listen 80;server_name blog.etiantian.org;location / {root html/blog;index index.php;
}location ~ .*\.(php|php5)?$ {root html/blog;fastcgi_pass 127.0.0.1:9000;fastcgi_index index.php;include fastcgi.conf;}
}
2、web2（apache-10.0.0.8）配置基于域名的虚拟主机（以下配置了3个虚拟主机）
[root@Oldboy extra]# egrep -v "#|^$" httpd-vhosts.conf NameVirtualHost *:80
<VirtualHost *:80>ServerAdmin oldboy@oldboyedu.comDocumentRoot "/application/apache2.2.31/htdocs/www"ServerName www.etiantian.orgServerAlias etiantian.orgErrorLog "/app/logs/www-error_log"CustomLog "/app/logs/www-access_log" common
</VirtualHost>
<VirtualHost *:80>ServerAdmin oldboy@oldboyedu.comDocumentRoot "/application/apache2.2.31/htdocs/bbs"ServerName bbs.etiantian.orgErrorLog "/app/logs/bbs-error_log"CustomLog "/app/logs/bbs-access_log" common
</VirtualHost>
<VirtualHost *:80>ServerAdmin oldboy@oldboyedu.comDocumentRoot "/application/apache2.2.31/htdocs/blog"ServerName blog.etiantian.orgErrorLog "/app/logs/blog-error_log"CustomLog "/app/logs/blog-access_log" common
</VirtualHost>
3、负载均衡器（LB-nginx-10.0.0.6）配置反向代理
[root@Oldboy conf]# cat nginx.conf
worker_processes 1;
events {worker_connections 1024;
}
http {include mime.types;default_type application/octet-stream;sendfile on;keepalive_timeout 65;upstream web_pool ｛ 地址池server 10.0.0.7:80 weight=1;server 10.0.0.8:80 weight=1;
}server {listen 80;server_name www.etiantian.org bbs.etiantian.org blog.etiantian.org;#ssl on;#ssl_certificate /usr/local/nginx/conf/33iq.crt;#ssl_certificate_key /usr/local/nginx/conf/33iq_nopass.key;location / {index index.html index.htm;proxy_pass http://web_pool; 反向代理到地址池proxy_set_header Host $host; 将请求头信息也一起反代给后端的服务器proxy_set_header X-Forwarded-For $remote_addr; 将客户端的真实ip映射到后端的web服务器中}}}解释：
当客户端分别访问 www.etiantian.org 、 bbs.etiantian.org、 blog.etiantian.org 时，nginx会带着这些主机头请求后端web集群，web服务器中的虚拟主机会自动识别nginx请求的主机头，并回复nginx请求，nginx再将web端的回复，交给客户端。也可以代理单台服务器：
location / {index index.html index.htm;proxy_pass http://172.16.100.100; proxy_set_header Host $host; proxy_set_header X-Forwarded-For $remote_addr; }
4、修改web端日志访问ip
默认情况下web端日志记录的访问ip是负载均衡器的ip，所以需要修改为真实客户端ip
(1) 负载均衡器（LB）配置
server {listen 80;server_name blog.etiantian.org;location / {index index.html index.htm;proxy_pass http://blog_pool; 代理blog动态页面proxy_set_header Host $host;proxy_set_header X-Forwarded-For $remote_addr; 负载均衡器开启ip转发，将客户端ip映射到web服务器}}
(2) web1端修改日志格式来接收客户端的真实ip（nginx主配置文件）
cat nginx.conflog_format main '$http_x_forwarded_for $remote_addr - $remote_user [$time_local] "$request" ''$status $body_bytes_sent "$http_referer" ''"$http_user_agent"';
(3) web2端修改日志格式来接收客户端的真实ip （apache主配置文件）
LogFormat "%{X-Forwarded-For}i %h %l %u %t \"%r\" %>s %b" common
