基于VMware环境Linux服务器集群方案--LVS+Keepalived (2)

在上文中《基于VMware环境Linux服务器集群方案--LVS+Keepalived (1)》，其实仅使用了三台服务器（1LB+2Real Server），一旦LB挂掉，则整个服务瘫痪。或者Real Server的某台服务器挂掉，LB依然会将部分用户分配到这个服务器而使该用户无法访问。如何保证LVS服务器集群的高可用性呢？

本文将采用LVS+Keepalived，并增加一台Backup 服务器以备LB无法提供服务时自动接管负载均衡工作的方案。当然你也可以采用LVS+Heartbeat+Ldirectord方案，不过该方案配置比Keepalived稍显复杂（可参考文章：双机热备份及高密度集群）。

一、服务器设置及IP分配：（详细拓扑图请查看上文）

Virtual IP：192.168.195.10 -- 虚拟服务器IP，用户通过该IP入口

Load Balancer(Active Router)：192.168.195.3 -- 真实服务器IP

Backup Router：192.168.195.4 -- 备份服务器IP

Real Server 1：192.168.195.5 -- WEB服务器IP

Real Server 2：192.168.192.6 -- WEB服务器IP

二、安装配置Keepalived

1、下载Keepalived最新版本，下载地址：http://www.keepalived.org/download.html，eg:keepalived-1.1.20.tar.gz，在Load Balancer和Backup Router均需安装Keepalived，安装过程如下：

#tar -zvxf keepalived-1.1.20.tar.gz

#cd keepalived-1.1.20

#./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/
#service keepalived start|stop #做成系统启动服务方便管理

2、配置Keepalived，#vim /etc/keepalived/keepalived.conf，内容如下：

! Configuration File for keepalived

global_defs {
notification_email {
admin@admin.com #接收Real Server 失效通知信息
}
notification_email_from lvs@admin.com
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL_1 #Backup服务器将此项改为LVS_DEVEL_2
}

vrrp_instance VI_1 {
state MASTER #Backup服务器将此项改为BACKUP
interface eth0
virtual_router_id 51
priority 150 #Backup服务器将此项改为100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.195.10 #VIP
}
}

virtual_server 192.168.195.10 80 {
delay_loop 6
lb_algo wrr
lb_kind DR
persistence_timeout 50
protocol TCP

real_server 192.168.195.5 80 { #Real Server 1
weight 3
TCP_CHECK {
connect_timeout 10
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}

real_server 192.168.195.6 80 { #Real Server 2
weight 3
TCP_CHECK {
connect_timeout 10
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
}

3、运行Keepalived，在运行Keepalived之前，请先把上文中"lvsDR"脚本删除或停止运行。在Load Balancer和Backup Router分别执行：#service keepalived start。在浏览器输入http://192.168.195.10即可查看效果。关闭Load Balancer服务器，LVS将会自动切换至Backup Router。

三、错误调试

1、 keepalived的日志可以查看/var/log/messages中，命令：#tail -f /var/log/messages
2、在同一网段内virtual_router_id 值不能相同，如果相同会在messages中收到VRRP错误包，如下所示：
Mar 9 07:32:52 keepalivet2 Keepalived_vrrp: VRRP_Instance(VI_1) Dropping received VRRP packet...
Mar 9 07:32:53 keepalivet2 Keepalived_vrrp: ip address associated with VRID not present in received packet : 1992032266
Mar 9 07:32:53 keepalivet2 Keepalived_vrrp: one or more VIP associated with VRID mismatch actual MASTER advert
Mar 9 07:32:53 keepalivet2 Keepalived_vrrp: bogus VRRP packet received on eth0 !!!

解决办法：修改virtual_router_id的值，记住MASTER和BACKUP服务器的virtual_router_id值要相同，重启服务即可。

参考文档：

Keepalived手册：http://www.sanotes.net/html/y2009/331.html

CentOS5.2上配置Keepalived+LVS集群(DR模式)：http://hi.baidu.com/lanbo0829/blog/item/b308f38a04614498a4c272de.html

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