参考文章：
http://www.cnblogs.com/holbrook/archive/2012/10/25/2738475.html
http://blog.zhuyin.org/866.html
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
- 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.gz cd nginx-1.2.4 ./configure --with-http_stub_status_module make && make install
- 安装keepalived
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_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 keepalived global_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 keepalived global_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:
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 }
主nginx负载均衡器：172.26.11.99 （通过keepalived配置了VIP：172.26.11.101供外使用）
副nginx负载均衡器：172.26.11.100 （通过keepalived配置了VIP：172.26.11.101供外使用）
后端web服务器：
172.26.11.73
172.26.11.74
一、172.26.11.99 以及 172.26.11.100的关键nginx配置如下：
vim /etc/nginx/nginx.conf
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#################
....
upstream www.xxx.com {
server 172.26.11.73:8080 max_fails=1;#max_fails 表示健康检查失败的次数，这里表示次数为一次，即标记该服务器down了
server 172.26.11.74:8080 max_fails=1;
}
server
{
listen 80;
server_name www.xxx.com;
location / {
proxy_next_upstream error timeout http_500 http_502 http_504; #这里表示健康检查涉及到的情形，有这些情形的，都切换到另外的web服务器访问
proxy_read_timeout 10s; #这里表示程序返回的时间，请参考php.ini的max_exe_time来设置。
proxy_pass http://www.xxx.com;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
#access_log /var/log/nginx/xxx.log;
}
##########################
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二、安装keepalive (centos)
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#安装 popt
yum -y install popt popt-devel
cd /data/software
wget http://www.keepalived.org/software/keepalived-1.2.8.tar.gz
cd /data/src
tar zxf ../software/keepalived-1.2.8.tar.gz
cd keepalived-1.2.8
./configure --prefix=/usr/local/keepalived --sysconf=/etc
make && make install
cp /usr/local/keepalived/sbin/keepalived /bin/
chkconfig --add keepalived
#设置开机启动
chkconfig keepalived on
#启动keepalive服务
/etc/init.d/keepalived start
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如果是ubuntu 直接 apt-get install keepalived 吧….
三、keepalive设置
cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf_bak
MASTER
vim /etc/keepalived/keepalived.conf
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! Configuration File for keepalived
global_defs {
notification_email {
admin@test.com
}
notification_email_from admin@test.com
smtp_server xxx.smtp.com
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_script Monitor_Nginx {
script "/root/monitor_nginx.sh"
interval 2
weight 2
}
vrrp_instance VI_1 {
state MASTER #(主机为MASTER，备用机为BACKUP)
interface eth0 #(HA监测网络接口)
virtual_router_id 61 #(主、备机的virtual_router_id必须相同)
#mcast_src_ip 172.26.11.99 #(多播的源IP，设置为本机外网IP，与VIP同一网卡)此项可不设置
priority 90 #(主、备机取不同的优先级，主机值较大，备份机值较小,值越大优先级越高)
advert_int 1 #(VRRP Multicast广播周期秒数)
authentication {
auth_type PASS #(VRRP认证方式)
auth_pass 1234 #(密码)
}
track_script {
Monitor_Nginx #(调用nginx进程检测脚本)
}
virtual_ipaddress {
172.26.11.101 #(VRRP HA虚拟地址)
}
}
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BACKUP方面只需要修改state为BACKUP , priority比MASTER稍低即可
四、监控nginx进程的脚本：monitor_nginx.sh 内容如下：
vim /root/monitor_nginx.sh
当检测到nginx进程不存在的时候，就干掉所有的keepalived，这时候，请求将会由keepalived的backup接管！！
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#!/bin/bash
if [ "$(ps -ef | grep "nginx: master process"| grep -v grep )" == "" ]
then
killall keepalived
fi
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chmod +x /root/monitor_nginx.sh
172.26.11.99 172.26.11.100都重新启动keepalived：
service keepalived restart
这里请注意，当keepalived启动后，我们可以用命令：
ip add show eth0 来看我们的eth0网卡确实被添加了虚拟IP，如下图：
完毕，可以测试了！
------------正 文 已 结 束， 感 谢 您 的 阅 读 （折雨的天空）--------------------
转载请注明本文标题和链接：《用nginx和keepalived配置了一个简单的负载均衡》
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