LVS（DR） + Keepalived 实现负载均衡高可用
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。
一、环境说明
本次试验使用的是2台前端代理服务器(LVS) 加上 keepalived，后端为了方便，使用apache来发布网页，达到测试的目的。
操作系统：centos7 64位
软件源：阿里云
2台服务器（LVS1、LVS2）安装 keepalived 和安装LVS 来反向代理
2台服务器（web1、web2）安装 apache 来提供服务
服务器的防火墙和selinux全部关闭
LVS1 IP：192.168.163.158
LVS2 IP：192.168.163.161
web1 IP：192.168.163.159
web2 IP：192.168.163.160
虚拟IP： 192.168.163.200
拓扑图如下：
二、环境安装
首先配置web服务器
1、首先为后端的2台web服务器安装apache
[root@web1 ~]# yum install -y httpd
[root@web2 ~]# yum install -y httpd
2、创建各自的网页
[root@web1 ~]# echo "web1：192.168.163.159" > /var/www/html/index.html
[root@web2 ~]# echo "web2：192.168.163.160" > /var/www/html/index.html
3、启动服务
[root@web1 ~]# systemctl start httpd
[root@web2 ~]# systemctl start httpd
4、编写脚本，为web服务器设置虚拟IP以及设置抑制ARP包
[root@web1 ~]# vim /root/VIP.sh
#!/bin/bash
VIP=192.168.163.200 #这个为你要设置的VIP
case $1 in
start)
ifconfig lo:0 $VIP netmask 255.255.255.255 broadcast $VIP
/sbin/route add -host $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 $IP >/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
添加执行权限并执行该脚本
[root@web1 ~]# chmod a+x VIP.sh
[root@web1 ~]# bash /root/VIP.sh start
在web2上也执行该操作
在LVS服务器安装 LVS 和 Keepalived
1、安装软件包
[root@LVS1 ~]# yum install -y ipvsadm keepalived
[root@LVS2 ~]# yum install -y ipvsadm keepalived
2、编辑 LVS1的 keepalived 配置文件
[root@LVS1 ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
root@localhost
}
notification_email_from keepalived@localhost
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS
vrrp_mcast_group4 224.0.100.19
}
vrrp_instance VI_1 {
state BACKUP
interface ens32
virtual_router_id 51
priority 100
nopreempt
advert_int 1
authentication {
auth_type PASS
auth_pass xhk
}
virtual_ipaddress {
192.168.163.200 dev ens32
}
}
virtual_server 192.168.163.200 80 { # 定义转移ip端口80的集群服务
delay_loop 3
lb_algo rr
lb_kind DR
protocol TCP
sorry_server 127.0.0.1 80
real_server 192.168.163.159 80 { # 定义集群服务包含的RS 1
weight 1 # 权重为1
HTTP_GET { # 定义RS1的健康状态检测
url {
path /
status_code 200
}
connect_timeout 1
nb_get_retry 3
delay_before_retry 1
}
}
real_server 192.168.163.160 80 { # 定义集群服务包含的RS 2
weight 1 # 权重为1
HTTP_GET { # 定义RS2的健康状态检测
url {
path /
status_code 200
}
connect_timeout 1
nb_get_retry 3
delay_before_retry 1
}
}
}
3、编辑 LVS2的 keepalived 配置文件
[root@LVS2 ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
root@localhost
}
notification_email_from keepalived@localhost
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS
vrrp_mcast_group4 224.0.100.19
}
vrrp_instance VI_1 {
state BACKUP
interface ens32
virtual_router_id 51
priority 99
nopreempt
advert_int 1
authentication {
auth_type PASS
auth_pass xhk
}
virtual_ipaddress {
192.168.163.200 dev ens32
}
}
virtual_server 192.168.163.200 80 { # 定义转移ip端口80的集群服务
delay_loop 3
lb_algo rr
lb_kind DR
protocol TCP
sorry_server 127.0.0.1 80
real_server 192.168.163.159 80 { # 定义集群服务包含的RS 1
weight 1 # 权重为1
HTTP_GET { # 定义RS1的健康状态检测
url {
path /
status_code 200
}
connect_timeout 1
nb_get_retry 3
delay_before_retry 1
}
}
real_server 192.168.163.160 80 { # 定义集群服务包含的RS 2
weight 1 # 权重为1
HTTP_GET { # 定义RS2的健康状态检测
url {
path /
status_code 200
}
connect_timeout 1
nb_get_retry 3
delay_before_retry 1
}
}
}
2个配置文件不同的只是优先级的不同，分出MASTER，并且设置了不抢占模式，为的是防止业务切换国语频繁！
4、开启路由转发
[root@LVS1 ~]# echo "1" /proc/sys/net/ipv4/ip_forward
[root@LVS2 ~]# echo "1" /proc/sys/net/ipv4/ip_forward
5、设置虚拟IP
[root@LVS1 ~]# ifconfig lo:0 192.168.163.200 broadcast 192.168.163.200 netmask 255.255.255.255 up
[root@LVS2 ~]# ifconfig lo:0 192.168.163.200 broadcast 192.168.163.200 netmask 255.255.255.255 up
6、启动keepalived服务
[root@LVS1 ~]# systemctl restart keepalived
[root@LVS2 ~]# systemctl restart keepalived
三、测试环节
1、查看keepalived状态
[root@LVS1 ~]# systemctl status keepalived
● keepalived.service - LVS and VRRP High Availability Monitor
Loaded: loaded (/usr/lib/systemd/system/keepalived.service; disabled; vendor preset: disabled)
Active: active (running) since Sun 2017-10-22 01:26:32 EDT; 3min 48s ago
Process: 2656 ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 2657 (keepalived)
CGroup: /system.slice/keepalived.service
├─2657 /usr/sbin/keepalived -D
├─2658 /usr/sbin/keepalived -D
└─2659 /usr/sbin/keepalived -D
Oct 22 01:26:37 LVS1 Keepalived_vrrp[2659]: Sending gratuitous ARP on ens32 for 192.168.163.200
查看虚拟IP
[root@LVS1 ~]# ip addr sh
1: lo:
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet 192.168.163.200/32 brd 192.168.163.200 scope global lo:0
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens32:
link/ether 00:0c:29:5f:46:a6 brd ff:ff:ff:ff:ff:ff
inet 192.168.163.158/24 brd 192.168.163.255 scope global dynamic ens32
valid_lft 1654sec preferred_lft 1654sec
inet 192.168.163.200/32 scope global ens32
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe5f:46a6/64 scope link
valid_lft forever preferred_lft forever
访问网页
[root@client ~]# curl 192.168.163.200
web1：192.168.163.159
[root@client ~]# curl 192.168.163.200
web2：192.168.163.160
将LVS1的Keepalived停掉
[root@LVS1 ~]# systemctl stop keepalived
可以看到LVS拿到了VIP
[root@LVS2 ~]# systemctl status keepalived
● keepalived.service - LVS and VRRP High Availability Monitor
Loaded: loaded (/usr/lib/systemd/system/keepalived.service; disabled; vendor preset: disabled)
Active: active (running) since Sun 2017-10-22 01:26:38 EDT; 6min ago
Process: 2553 ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 2555 (keepalived)
CGroup: /system.slice/keepalived.service
├─2555 /usr/sbin/keepalived -D
├─2556 /usr/sbin/keepalived -D
└─2557 /usr/sbin/keepalived -D
Oct 22 01:32:50 LVS2 Keepalived_vrrp[2557]: Sending gratuitous ARP on ens32 for 192.168.163.200
继续访问网页
[root@client ~]# curl 192.168.163.200
web1：192.168.163.159
[root@client ~]# curl 192.168.163.200
web2：192.168.163.160
测试成功！！！！！！！！！！！！！！！！！！！