nginx + keepalive 实现高可用负载均衡

一、拓扑环境：

主nginx负载均衡器 192.168.166.203
辅nginx负载均衡器 192.168.166.177
VIP地址 192.168.166.178

http://www.keepalived.org/download.html
tar -zxvf keepalived-1.2.1.tar.gz
cd keepalived-1.2.1
./configure --prefix=/usr/local/keepalived --sysconf=/etc

make && make install

cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
cp /usr/local/keepalived/sbin/keepalived /bin/
chkconfig --add keepalived
chmod 755 /etc/init.d/keepalived
chkconfig keepalived on
service keepalived start

二．修改配置文件为以下内容:　[master slave]
MASTER
vim /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {

notification_email {
[email protected]
}

notification_email_from [email protected]
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 192.168.166.203 #(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 {
192.168.166.178 #(VRRP HA虚拟地址)
}
}

###BACKUP方面只需要修改state为BACKUP , priority比MASTER稍低就OK了

三：注：monitor_nginx.sh为监控nginx进程的脚本,内容如下

#!/bin/bash
if [ "$(ps -ef | grep "nginx: master process"| grep -v grep )" == "" ]
then
/usr/local/nginx/sbin/nginx
sleep 5
if [ "$(ps -ef | grep "nginx: master process"| grep -v grep )" == "" ]
then
killall keepalived
fi
fi

#chmod +x monitor_nginx.sh

四.启动keepalived
service keepalived start
或
/usr/local/keepalived/sbin/keepalived -D -f /etc/keepalived/keepalived.conf

五．测试步骤

1． 访问VIP看是否能够正常访问后端的web
2． 停止其中一个web看是否能将访问转到另一台上
3． 停止两台nginx上任何一个nginx进程看监控进程脚本是否会自动启动nginx
4． 停止任何一台nginx上的keepalived进程看另一台是否接管vip

track_interface的意思是将Linux中你想监控的网络接口卡监控起来，当其中的一块出现故障是keepalived都将视为路由器出现故障。
这里请注意： virtual_router_id 61，同一组master/backup中，也就是如果你设置了多个VRRP，同一组这个ID必须相同，不然启动的时候主从都会把VIP给启动了

keepalived 通过发送和接收组播包中的同一个virtual_router_id 的中的成员的存活，来确定对方的不可用，一旦检测到对方的不可用，即会切换它的备份角色为主。
即：当真实机192.168.166.177上的keepalived 检测到 真实机192.168.166.203上的keepalived 不可用时，177上将使用vip:192.168.166.178对外服务并由backup角色转变为master

keepalived+nginx实现 HA与负载均衡中keepalived负责实现HA功能，控制VIP(虚拟网络地址)转移功能，nginx实现对realserver七层负载均衡功能，nginx提供代理服务和cache功能，DNS服务可以负责前段VIP的负载均衡。

keepalived的配置
192.168.200.1 keepalived配置
! Configuration File for keepalived

global_defs {
notification_email {
[email protected]
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_TEST_YDQ
}

vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 61
priority 150
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.200.101/24 dev eth0 label eth0:0
}
}

vrrp_instance VI_2 {
state BACKUP
interface eth0
virtual_router_id 62
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 2222
}
virtual_ipaddress {
192.168.200.102/24 dev eth0 label eth0:1
}
}

vrrp_instance VI_3 {
state BACKUP
interface eth0
virtual_router_id 63
priority 50
advert_int 1
authentication {
auth_type PASS
auth_pass 3333
}
virtual_ipaddress {
192.168.200.103/24 dev eth0 label eth0:1
}
}

nginx配置 ：

user nobody nobody;                                                          
worker_processes 1;                                                          
                                                                             
#error_log logs/error.log;                                                   
#error_log logs/error.log notice;                                            
error_log logs/error.log debug;                                              
                                                                             
pid logs/nginx.pid;                                                          
                                                                             
                                                                             
events {                                                                     
use epoll;                                                                   
worker_connections 1024;                                                     
}                                                                            
                                                                             
                                                                             
http {                                                                       
include mime.types;                                                          
default_type application/octet-stream;                                       
                                                                             
log_format main '$remote_addr - $remote_user [$time_local] "$request" '      
'$status $body_bytes_sent "$http_referer" '                                  
'"$http_user_agent" "$http_x_forwarded_for"';                                
                                                                             
access_log logs/access.log main;                                             
                                                                             
sendfile on;                                                                 
#tcp_nopush on;                                                              
                                                                             
#keepalive_timeout 0;                                                        
keepalive_timeout 65;                                                        
                                                                             
gzip on;                                                                     
gzip_min_length 1k;                                                          
gzip_buffers 6 16k;                                                          
gzip_http_version 1.1;                                                       
gzip_comp_level 2;                                                           
gzip_types text/plain application/x-javascript text/css application/xml;     
gzip_vary on;                                                                
# location / {                                                               
# root html;                                                                 
# index index.html index.htm;                                                
# }                                                                          
error_page 404 /404.html;                                                    
                                                                             
upstream www.test.com {                                                      
server 192.168.11.37:80;                                                     
server 192.168.11.38:80;                                                     
}                                                                            
                                                                             
server                                                                       
{                                                                            
listen 80;                                                                   
server_name www.test.com 192.168.166.178;                                    
index index.htm index.html;                                                  
#root /web/wwwroot;                                                          
                                                                             
location / {                                                                 
proxy_pass http://www.test.com;                                              
proxy_next_upstream http_500 http_502 http_503 error timeout invalid_header; 
proxy_set_header Host $host;                                                 
proxy_set_header X-Real-IP $remote_addr;                                     
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;                 
include proxy.conf;                                                          
}                                                                            
log_format blog_test_com '$remote_addr - $remote_user [$time_local] $request '
'"$status" $body_bytes_sent "$http_referer" '                                
'"$http_user_agent" "$http_x_forwarded_for"';                                
access_log logs/blog_test_com;                                               
}                                                                            
}