---------------------这里非常感谢田逸老师的文档，在我学习lvs的时候给了我很大的帮助！
一、为什么要使用负载均衡技术？
1、系统高可用性
2、 系统可扩展性
3、 负载均衡能力
LVS+keepalived能很好的实现以上的要求，LVS提供负载均衡，keepalived提供健康检查，故障转移，提高系统的可用性！采用这样的架构以后很容易对现有系统进行扩展，只要在后端添加或者减少realserver，只要更改lvs的配置文件，并能实现无缝配置变更！
二、LVS+Keepalived介绍
1、 LVS
LVS是一个开源的软件，可以实现LINUX平台下的简单负载均衡。LVS是Linux Virtual Server的缩写，意思是Linux虚拟服务器。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）。
2、 keepalived
Keepalived 是运行在lvs 之上，它的主要功能是实现真实机的故障隔离及负载均衡器间的失败切换，提高系统的可用性
三、LVS+keepalived负载均衡架构图
四、LVS+keepalived的安装和配置
1. 配置环境
System OS：CentOS release 5.4
Software：ipvsadm-1.24.tar.gz, keepalived-1.1.19.tar.gz
2. 信息列表
| 名称 |
IP |
| LVS-Master |
192.168.1.112 |
| LVS-BACKUP |
192.168.1.113 |
| LVS-VIP |
192.168.1.115 |
| Realserver1 |
192.168.1.105 |
| Realserver2 |
192.168.1.103 |
| Realserver3 |
192.168.1.104 |
3. 安装lvs
分别在backup lvs和master lvs上安装
wget http://www.linuxvirtualserver.org/software/kernel-2.6/ipvsadm-1.24.tar.gz
ln -s /usr/src/kernels/2.6.18-164.el5-i686/ /usr/src/linux
tar zxvf ipvsadm-1.24.tar.gz
cd ipvsadm-1.24
make && make install
4. 安装keepalived
分别在backup lvs和master lvs上安装
wget http://www.keepalived.org/software/keepalived-1.1.19.tar.gz
tar zxvf keepalived-1.1.19.tar.gz
cd keepalived-1.1.19
./configure --prefix=/usr/local/keepalived
make
make install
cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
mkdir /etc/keepalived
5. 配置keepadlived
LVS-Master的配置文件如下
[root@linux5 ~]# cat /etc/keepalived/keepalived.conf
global_defs {
notification_email {
[email protected] #email 通知
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS1 # 设置lvs的id，在一个网络内应该是唯一的
}
vrrp_sync_group test { #设置vrrp组
group {
loadbalance
}
}
vrrp_instance loadbalance {
state MASTER #设置lvs的状态，报错MASTER和BACKUP两种，必须大写
interface eth0 #设置对外服务的接口
lvs_sync_daemon_inteface eth0 #设置lvs监听的接口
virtual_router_id 51 #设置虚拟路由表示
priority 180 #设置优先级，数值越大，优先级越高
advert_int 5 #设置同步时间间隔
authentication { #设置验证类型和密码
auth_type PASS
auth_pass 1111
}
virtual_ipaddress { #设置lvs vip
192.168.1.115
}
}
virtual_server 192.168.1.115 80 {
delay_loop 6 #健康检查时间间隔
lb_algo rr #负载均衡调度算法
lb_kind DR #负载均衡转发规则
#persistence_timeout 20 #设置会话保持时间，对bbs等很有用
protocol TCP #协议
real_server 192.168.1.105 80 {
weight 3 #设置权重
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
real_server 192.168.1.103 80 {
weight 3
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
real_server 192.168.1.104 80 {
weight 3
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
}
LVS-backup的配置文件如下
global_defs {
notification_email {
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS2
}
vrrp_sync_group test {
group {
loadbalance
}
}
vrrp_instance loadbalance {
state BACKUP
interface eth0
lvs_sync_daemon_inteface eth0
virtual_router_id 51
priority 150
advert_int 5
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.1.115
}
}
virtual_server 192.168.1.115 80 {
delay_loop 6
lb_algo rr
lb_kind DR
#persistence_timeout 20
protocol TCP
real_server 192.168.1.105 80 {
weight 3
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
real_server 192.168.1.103 80 {
weight 3
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
real_server 192.168.1.104 80 {
weight 3
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
}
6. Realserver的配置
三台客户端的脚本都一样！
cat /etc/rc.d/init.d/realserver.sh
#!/bin/bash
# description: Config realserver lo and apply noarp
SNS_VIP=192.168.1.115
/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
7. 测试
1) 首先测试各个readserver，确定各个readserver都能正常访问，测试realserver.sh脚本，看启动后能不能绑定lvs vip，停止后能不能去除绑定的vip
2) 测试lvs能否进行负载均衡转发，利用ipvsadm命令查看，如果想只当当前的请求转发到哪个服务器去了，可以用ipvsadm加选项来查看，其完整形式为：ipvsadm –lcn | grep 192.168.1.115
3) 停掉主lvs看lvs backup是否接管！
4) 更详细信息请查看日志，tail -f /var/log/messages