CentOS5.2上Keepalived+LVS实现DR集群

以下内容均参考这篇文章：，IP地址和部分内容做了修改和增加。

 

一. LVS+Keepalived 介绍
LVS
LVS是Linux Virtual Server的简写，意即Linux虚拟服务器，是一个虚拟的服务器集群系统。本项目在1998年5月由章文嵩博士成立，是中国国内最早出现的自由软件项目之一。目前有三种IP负载均衡技术（VS/NAT、VS/TUN和VS/DR）；
八种调度算法（rr,wrr,lc,wlc,lblc,lblcr,dh,sh）。

Keepalvied
Keepalived在这里主要用作RealServer的健康状态检查以及LoadBalance主机和BackUP主机之间failover的实现

二. 网站负载均衡拓朴图
系统：CentOS5.2

LVS-DR-Master        10.129.60.185        
LVS-DR-BACKUP        10.129.60.188        
LVS-DR-VIP        10.129.60.199        
WEB1-Realserver        10.129.60.197        
WEB2-Realserver        10.129.60.198      
GateWay        10.129.60.129   

     

三. 安装LVS和Keepalvied软件包
安装LVS

#yum install ipvsadm

安装keepalived

#wget

#ln -s /usr/src/kernels/2.6.18-92.el5-i686 /usr/src/linux

#tar zxvf keepalived-1.1.15.tar.gz
#cd keepalived-1.1.15
#CFLAGS="-O3 -pipe" ./configure && make && make install
#find / -name keepalived  # 查看keepalived位置                
#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/
#chkconfig --level 23456 keepalived on    #做成系统启动服务方便管理.

 

四. 配置RealServer脚本

#vi /usr/local/sbin/realserver.sh 
#!/bin/bash
# description: Config realserver lo and apply noarp
#Written by :NetSeek [url=][/url]
     
SNS_VIP=10.129.60.199
   
. /etc/rc.d/init.d/functions
 
case "$1" in
start)
       ifconfig lo:0 $SNS_VIP netmask 255.255.255.255 broadcast $SNS_VIP
       /sbin/route add -host $SNS_VIP dev lo:0
       echo "1" >/proc/sys/net/ipv4/conf/lo/arp_ignore
       echo "2" >/proc/sys/net/ipv4/conf/lo/arp_announce
       echo "1" >/proc/sys/net/ipv4/conf/all/arp_ignore
       echo "2" >/proc/sys/net/ipv4/conf/all/arp_announce
       sysctl -p >/dev/null 2>&1
       echo "RealServer Start OK"
 
       ;;
stop)
       ifconfig lo:0 down
       route del $SNS_VIP >/dev/null 2>&1
       echo "0" >/proc/sys/net/ipv4/conf/lo/arp_ignore
       echo "0" >/proc/sys/net/ipv4/conf/lo/arp_announce
       echo "0" >/proc/sys/net/ipv4/conf/all/arp_ignore
       echo "0" >/proc/sys/net/ipv4/conf/all/arp_announce
       echo "RealServer Stoped"
        ;;
 *)
       echo "Usage: $0 {start|stop}"
       exit 1
esac
       
exit 0

 

#chmod 755 /usr/local/sbin/realserver.sh

#echo '/usr/local/sbin/realserver.sh start' >> /etc/rc.local

     

五．利用Keepalvied实现负载均衡和和高可用性

1.配置在主负载均衡服务器上配置keepalived.conf

产生用于健康检测的url的digest值

#genhash -s 10.129.60.197 -p 80 -u /hb.html

MD5SUM = 348099c57ebe33689c82198672f86984

#genhash -s 10.129.60.198 -p 80 -u /hb.html

MD5SUM = 348099c57ebe33689c82198672f86984
#vi /etc/keepalived/keepalived.conf

 ! Configuration File for keepalived

global_defs {
   notification_email {
     
   }
   notification_email_from 
   smtp_server 10.129.60.11
   smtp_connect_timeout 30
   router_id LVS_DEVEL
}

# 20081013 written by :netseek
# VIP1
vrrp_instance VI_1 {
    state BACKUP             #备份服务器上将MASTER改为BACKUP 
    interface eth0
    virtual_router_id 51
    priority 99    # 备份服务上将100改为99
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        10.129.60.199
        #(如果有多个VIP，继续换行填写.)
    }
}

virtual_server 10.129.60.199 80 {
    delay_loop 5                  #(每隔6秒查询realserver状态)
    lb_algo wrr                  #(lvs 算法)
    lb_kind DR                  #(Direct Route)
#    persistence_timeout 60        #(同一IP的连接60秒内被分配到同一台realserver)
    protocol TCP                #(用TCP协议检查realserver状态)

    sorry_server 127.0.0.1 80   #realserver全部失败，vip指向本机80端口。在VIP维护的时候非常有用

    real_server 10.129.60.197 80 {
        weight 3               #(权重)
        HTTP_GET {             #通过检查指定url的校验和是否正确来判断RealServer的健康状态
            url {
              path /hb.html
              digest 348099c57ebe33689c82198672f86984  #刚才genhash产生的md5值
            }
            connect_timeout 10
            nb_get_retry 3
            delay_before_retry 3
            connect_port 80
        }
    }
    real_server 10.129.60.198 80 {
        weight 3
        HTTP_GET {
            url {
              path /hb.html
              digest 348099c57ebe33689c82198672f86984  #刚才genhash产生的md5值
            }
            connect_timeout 10
            nb_get_retry 3
            delay_before_retry 3
            connect_port 80
        }
     }
}

      

2. BACKUP服务器同上配置，先安装lvs再按装keepalived,仍后配置/etc/keepalived/keepalived.conf，只需将红色标示的部分改一下即可.

3. 启动keepalived 服务
#/etc/init.d/keepalived start  #keepalived就能利keepalived.conf 配置文件，实现负载均衡和高可用.

4. 启动RealServer

#/usr/local/sbin/realserver.sh start

#service httpd start

 

5. 测试lvs服务是否正常

5.1 通过浏览器访问是否正常

5.2 多次刷新浏览器，在主LVS上看连接数变化

#watch ipvsadm -l

5.3 停止主LVS上的keepalived 看看备份keepalived是否正常接管服务

六．相关参考
1．LVS 基础知识汇总
LVS的算法介绍               
学习LVS的三种转发模式      
LVS中的IP负载均衡技术      
更多的请到 负载均衡版查看

 

2. keepalived使用gratuitous ARP技术实现VIP的漂移，无论在主lvs服务器还是备份lvs服务器上是看不到vip的。

gratuitous ARP的知识请参考：