LVS_DR实现（负载均衡）及LVS_DR+keepalived实现（高可用+负载均衡）

client->VS->RS->client(VS只做调度,RS为虚拟服务器)

LVS_DR原理图解：

优点：负载均衡器只负责将请求包分发给物理服务器，而物理服务器将应答包直接发给用户。所以，负载均衡器能处理 很巨大的请求量，这种方式，一台负载均衡能为 超过100台的物理服务器服务，负载均衡器不再是系统的瓶颈.

缺点：这种方式需要所有的DIR和RIP都在同一广播域；不支持异地容灾。

环境：

iptables和selinux关闭

test1(调度器)端(172.25.1.1)：

[root@test1 ~]# yum install -y ipvsadm

Loaded plugins: product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use
subscription-manager to register.
Setting up Install Process
No package ipvsadm available.
Error: Nothing to do

[root@test1 ~]# vim /etc/yum.repos.d/rhel-source.repo
[rhel6.5]
name=rhel6.5
baseurl=http://172.25.1.250/rhel6.5
gpgcheck=0
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
[LoadBalancer]                                               //添加LoadBalancer用来下载ipvsadm服务
name=LoadBalancer
baseurl=http://172.25.1.250/rhel6.5/LoadBalancer
gpgcheck=0
enabled=1

 [root@test1 ~]# yum install -y ipvsadm
[root@test1 ~]# /etc/init.d/ipvsadm start       //启动服务
[root@test1 ~]# ip addr add 172.25.1.100 dev eth0      //添加虚拟IP
[root@test1 ~]# ip addr    //查看是否添加
1: lo: mtu 16436 qdisc noqueue state
UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: mtu 1500 qdisc pfifo_fast
state UP qlen 1000
link/ether 52:54:00:4f:1c:32 brd ff:ff:ff:ff:ff:ff
inet 172.25.1.1/24 brd 172.25.1.255 scope global eth0
inet 172.25.1.100/32 scope global eth0inet6 fe80::5054:ff:fe4f:1c32/64 scope link
valid_lft forever preferred_lft forever
[root@test1 ~]# ipvsadm -A -t 172.25.1.100:80 -s rr            
[root@test1 ~]# ipvsadm -a -t 172.25.1.100:80 -r 172.25.1.2:80 -g        //-a表示在添加虚拟服务中添加，-g表示使用直接模式

[root@test1 ~]# ipvsadm -a -t 172.25.1.100:80 -r 172.25.1.3:80 -g

[root@test1 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port
Forward Weight ActiveConn InActConn
TCP 172.25.1.100:80 rr
-> 172.25.1.2:80   Route    1    0    0
-> 172.25.1.3:80   Route    1    0    0

 服务器 1(server2：172.25.1.2)端:

[root@test2 ~]# ip addr add 172.25.1.100/32 dev eth0      //添加虚拟ip，目的是让test1与其正常进行三次握手。
[root@test2 ~]# vim /var/www/html/index.html

www.westos.org-server2

/etc/init.d/httpd restart

服务器 2(server3：172.25.1.3)端:

[root@test3 ~]# ip addr add 172.25.1.100/32 dev eth0       //添加虚拟ip，目的是让test1与其正常进行三次握手。
[root@test3 ~]# vim /var/www/html/index.html

bbs.westos.org-server3

/etc/init.d/httpd restart

客户端访问:
      调度器 MAC 地址:52:54:00:4f:1c:32
      服务器 1(server2)端 MAC 地址:52:54:00:2b:85:5b
      服务器 2(server3)端 MAC 地址:52:54:00:98:3d:65
注意:访问结果会出现下面三种情况:

[root@foundation1 ~]# arp -d 172.25.1.100        //端开之前的连接
[root@foundation1 ~]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 ~]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 ~]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 ~]# arp -an | grep 100
? (172.25.1.100) at 52:54:00:2b:85:5b [ether] on br0

总结1：从MAC地址可以看出没有经过调度器,直接经过服务器 1 访问

[root@foundation1 ~]# arp -d 172.25.1.100
[r[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

oot@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

? (172.25.1.100) at 52:54:00:2b:85:5b [ether] on

总结2：从MAC地址可以看出没有经过调度器,直接经过服务器 2 访问

[root@foundation1 ~]# arp -d 172.25.1.100
[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server2

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server2

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 ~]# arp -an | grep 100
? (172.25.1.100) at 52:54:00:4f:1c:32 [ether] on br0

总结3：从 MAC 地址可以看出经过了调度器,所以轮询。
总结: 从三种情况可以发现，连接到的 ip(VS 和 两个RS 的 ip 都一样)是随机的,因为三台 server 在同一
VLAN 下具有相同的 vip,故不能保证每次都会访问调度器。

解决：为了解决上面这个问题,需要设置禁止访问连接 RS。

RS（test2） :

[root@test2 ~]# yum install arptables_jf -y          //下载服务arptables
[root@test2 ~]# arptables -A IN -d 172.25.1.100 -j DROP        //目的是不允许客户端直接连接RS1
[root@test2 ~]# arptables -A OUT -s 172.25.1.100 -j mangle --mangle-ip-s 172.25.1.2       //允许VS与RS1连接
[root@test2 ~]# /etc/init.d/arptables_jf save       //保存该策略
[root@test2 ~]# cat /etc/sysconfig/arptables      //查看所写策略
# Generated by arptables-save v0.0.8 on Thu Sep 27 22:31:05 2018
*filter
:IN ACCEPT [0:0]
:OUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0][0:0] -A IN -d 172.25.1.100 -j DROP
[0:0] -A OUT -s 172.25.1.100 -j mangle --mangle-ip-s 172.25.1.2
COMMIT
# Completed on Thu Sep 27 22:31:05 2018

RS（test3）与test2步骤相同 :

[root@test3 ~]# arptables -nL      //用于查看 arptables 的具体内容
[root@test3 ~]# yum install arptables_jf -y   
[root@test3 ~]# arptables -A IN -d 172.25.1.100 -j DROP            //目的是不允许客户端直接连接RS2
[root@test3 ~]# arptables -A OUT -s 172.25.1.100 -j mangle --mangle-ip-s 172.25.1.3      //允许VS与RS1连接
[root@test3 ~]# /etc/init.d/arptables_jf save       //保存该策略
[root@test3 ~]# cat /etc/sysconfig/arptables
[root@test3 ~]# arptables -nL     //用于查看 arptables 的具体内容
# Generated by arptables-save v0.0.8 on Thu Sep 27 22:31:09 2018
*filter
:IN ACCEPT [1:28]
:OUT ACCEPT [1:28]
:FORWARD ACCEPT [0:0]
[0:0] -A IN -d 172.25.1.100 -j DROP
[0:0] -A OUT -s 172.25.1.100 -j mangle --mangle-ip-s 172.25.1.3
COMMIT
# Completed on Thu Sep 27 22:31:09 2018

客户端测试（172.25.1.250）:
[root@foundation1 ~]# arp -an | grep 100
? (172.25.1.100) at 52:54:00:4f:1c:32 [ether] on br0
再次测试时 ip 的 mac 地址是VS 的

[root@foundation1 ~]# arp -d 172.25.1.100      //多次 down 掉后查看是否会依旧是VS的MAC地址
[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 ~]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 ~]# curl 172.25.1.100

www.westos.org-server2

问题：这种服务的缺点在于,如果后端服务器挂掉,比如说停掉 server 真实主机的 httpd 服务,
那么在客户端解析的时候们就会报错,但 server3 还会正常工作。这样用户就将得到错
误的信息:

[root@test2 ~]# /etc/init.d/httpd stop
Stopping httpd:
[ OK
[root@foundation1 ~]# curl 172.25.1.100
curl: (7) Failed connect to 172.25.1.100:80; Connection refused
[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 ~]# curl 172.25.1.100
curl: (7) Failed connect to 172.25.1.100:80; Connection refused
[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

总结： vs 对后端没有健康检查

解决这个问题的方法一:

   用 ldirectord 解决此问题

VS端:

[root@test1 ~]# vim /etc/yum.repos.d/rhel-source.repo                  //配置yum源，下载ldirectord服务
[HighAvailability]
name=HighAvailability
baseurl=http://172.25.1.250/rhel6.5/HighAvailability
gpgcheck=0

[root@test1 ~]# ls
ldirectord-3.9.5-3.1.x86_64.rpm
[root@test1 ~]# yum install * -y
[root@test1 ~]# rpm -ql ldirectord       //查看配置文件
/usr/share/doc/ldirectord-3.9.5/ldirectord.cf
[root@test1 ~]# cp /usr/share/doc/ldirectord-3.9.5/ldirectord.cf  /etc/ha.d/       //拷贝一份到/etc/ha.d/
[root@test1 ~]# cd /etc/ha.d
[root@sest1 ha.d]# ls
ldirectord.cf resource.d shellfuncs
[root@test1 ha.d]# vim ldirectord.cf          //修改配置文件
virtual=172.25.1.100:80            //虚拟vip
real=172.25.1.2:80 gate           //真实服务器1的ip
real=172.25.1.3:80 gate           //真实服务器1的ip
fallback=127.0.0.1:80 gate
service=http
scheduler=rr
#persistent=600
#netmask=255.255.255.255
protocol=tcpchecktype=negotiate
checkport=80
request="index.html"
#receive="Test Page"
#virtualhost=www.x.y.z

[root@test1 ha.d]# ipvsadm -ln      //列出规则
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port
Forward Weight ActiveConn InActConn
TCP 172.25.1.100:80 rr
Route    1    0    3    -> 172.25.1.2:80
Route    1    0    2    -> 172.25.1.3:80

[root@test1 ~]# ipvsadm -C    //清理规则
[root@test1 ~]# ipvsadm -l      //查看是否已经清除
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port
Forward Weight ActiveConn InActConn
[root@test1 ha.d]# /etc/init.d/ldirectord start        //再次打开服务又可以加载出规则
Starting ldirectord... success
[root@test1 ha.d]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port
Forward Weight ActiveConn InActConn
TCP 172.25.1.100:80 rr
Route    1    0    3    -> 172.25.1.2:80
Route    1    0    2    -> 172.25.1.3:80

[root@test1 ha.d]# vim /etc/httpd/conf/httpd.conf          //修改端口为80
Listen 80
[root@test1 ha.d]# /etc/init.d/httpd start           //重起服务
[root@test1 ha.d]# cd /var/www/html/        
[root@test1 html]# vim index.html         //编辑下面内容

网站正在维护中......

客户端测试：

[root@foundation1 ~]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 ~]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@test2 ~]# /etc/init.d/httpd stop        //若后台坏掉一个,则策略会自动更新
[root@test1 ha.d]# ipvsadm -ln                //可以看出已经实时更新坏掉的服务器
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port
Forward Weight ActiveConn InActConn
TCP 172.25.1.100:80 rr
-> 172.25.1.3:80
Route     1     0      2

客户端再次访问：

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 ~]# curl 172.25.1.100

bbs.westos.org-server3

若两个真实服务器都挂掉:

[root@test3 ~]# /etc/init.d/httpd stop
[root@test1 ha.d]# ipvsadm -ln                    //可以看出已经没有正常的服务器了
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port
Forward Weight ActiveConn InActConn
TCP 172.25.1.100:80 rr
-> 127.0.0.1:80
Local 1    0     0

此时客户端再次访问：

[root@foundation1 ~]# curl 172.25.1.100

网站正在维护中......

[root@foundation1 ~]# curl 172.25.1.100

网站正在维护中......

[root@foundation1 ~]# curl 172.25.1.100

网站正在维护中......

总结:
在客户端 curl 172.25.1.100 测试时, RS 轮询,当关闭 test2 时,只访问 test3,
RS 都关闭时会访问本地 test1,故显示“系统正在维护中......”

解决健康检查的方法二:

       用 keepalived 软件解决，

官网下载 keepalived 软件:http://www.keepalived.org/download.html

两个VS分别为：
主:test1
备:test4
VS 端分别安装 keepalived:

1.   安装keepalived服务

2.   ./configure -->openssl-devel -->  make --> make install

在主VR:test1下载keepalived服务

[root@test1 ~]# ls
keepalived-2.0.6.tar.gz
[root@test1 ~]# tar zxf keepalived-2.0.6.tar.gz                //解压压缩包
[root@test1 ~]# ls
keepalived-2.0.6 keepalived-2.0.6.tar.gz
[root@test1 keepalived-2.0.6]# ./configure --prefix=/usr/local/keepalived
--with-init=SYSV
[root@test1 keepalived-2.0.6]# yum install openssl-devel
[root@test1 keepalived-2.0.6]# ./configure --prefix=/usr/local/keepalived
--with-init=SYSV
[root@test1 keepalived-2.0.6]# make        //编译
[root@test1 keepalived-2.0.6]# make install
[root@test1 keepalived-2.0.6]# ln -s
/usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
[root@test1 keepalived-2.0.6]# ln -s /usr/local/keepalived/etc/keepalived/
/etc/
[root@test1 keepalived-2.0.6]# ln -s
/usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
[root@test1 keepalived-2.0.6]# ln -s /usr/local/keepalived/sbin/keepalived
/sbin/
[root@test1 keepalived-2.0.6]# cd /usr/local/
[root@test1 init.d]# chmod +x keepalived           //给keepalived执行权限
[root@test1 init.d]# /etc/init.d/keepalived start    //开启keepalived服务

在备VR:test4

创建一个虚拟机(test4:172.25.1.4),在备VR:test4下载与 test1 相同的服务 keepalived服务：

[root@test4 ~]# yum install openssh-clients -y
[root@test1 local]# scp -r keepalived/ [email protected]:/usr/local/       //将test1已经下载好的keepalived传给 test4
[root@test4 local]# ls
bin etc games include keepalived lib lib64 libexec sbin share src
[root@test4 ~]# ln -s /usr/local/keepalived/etc/rc.d/init.d/keepalived/etc/init.d/
[root@test4 local]# ln -s /usr/local/keepalived/etc/keepalived/ /etc/
[root@test4 local]# ln -s /usr/local/keepalived/etc/sysconfig/keepalived
/etc/sysconfig/
[root@test4 local]# ln -s /usr/local/keepalived/sbin/keepalived /sbin/
[root@test4 keepalived]# /etc/init.d/keepalived start

[root@test1 keepalived]# cd /etc/keepalived/
[root@test1 keepalived]# yum install mailx -y          //下载邮件服务
[root@test1 keepalived]# ip addr del 172.25.1.100/24 dev eth0      //删除虚拟ip
[root@test1 keepalived]# /etc/init.d/ldirectord stop
[root@test1 keepalived]# ip addr
1: lo: mtu 16436 qdisc noqueue state
UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: mtu 1500 qdisc pfifo_fast
state UP qlen 1000
link/ether 52:54:00:4f:1c:32 brd ff:ff:ff:ff:ff:ff
inet 172.25.1.1/24 brd 172.25.1.255 scope global eth0              //可以看到没有虚拟ip
inet6 fe80::5054:ff:fe4f:1c32/64 scope link

[root@test1 keepalived]# vim keepalived.conf            //修改内容
! Configuration File for keepalived
global_defs {
notification_email {
root@localhost      
}
notification_email_from [email protected]
smtp_server 172.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
vrrp_skip_check_adv_addr
#vrrp_strict            //放弃修改防火墙规则

vrrp_garp_interval 0
vrrp_gna_interval 0
}
vrrp_instance VI_1 {

state MASTER         //MASTER表示主模式
interface eth0
virtual_router_id 1     
priority 100            //数值越大，优先级越高

advert_int 1
aauthentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
172.25.1.100           //虚拟ip地址
}
}
virtual_server 172.25.1.100 80 {            //虚拟ip地址 ，服务启动生效时会自动添加
delay_loop 6          //对后端的健康检查时间
lb_algo rr
lb_kind DR              //DR模式

#persistence_timeout 50          //注释持续连接 
protocol TCP
}
real_server 172.25.1.2 80 {        //RS1的ip
weight 1
TCP_CHECK {
connect_timeout 3
retry 3
delay_before_retry 3
}
}
real_server 172.25.1.3 80 {       //RS2的ip
weight 1
TCP_CHECK {
connect_timeout 3
retry 3
delay_before_retry 3
}
}

[root@test1 keepalived]# /etc/init.d/keepalived restart

[root@test1 keepalived]# scp keepalived.conf [email protected]:/etc/keepalived/          //将配置文传给test4
[root@test4 keepalived]# cd /etc/keepalived/

[root@test4 keepalived]# yum install mailx -y
[root@test4 keepalived]# vim keepalived.conf
vrrp_instance VI_1 {
state BACKUP           //该为备模式
interface eth0
virtual_router_id 1 
priority 50                  //优先级要小于 test1 的优先级

[root@test4 keepalived]# >/var/log/messages    //清空日志
[root@test4 keepalived]# /etc/init.d/keepalived restart         //重起服务
[root@test4 keepalived]# cat /var/log/messages          //查看日志，可以看出test4做了BACKUP模式

客户端测试:

此时 test1 和 test4 的 keepalived 都是开启状态,其中 test1 做主,test4 做备

[root@foundation1 lvs]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 lvs]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 lvs]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 lvs]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 lvs]# arp -an | grep 100
? (172.25.1.100) at 52:54:00:4f:1c:32 [ether] on br0

从 MAC 地址可以看出走的是 test1。
若将 test1 的 keepalive 挂掉,则客户端依旧可以正常访问

[root@test1 keepalived]# /etc/init.d/ipvsadm stop
[root@foundation1 lvs]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 lvs]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 lvs]# curl 172.25.1.100

bbs.westos.org-server3

[root@foundation1 lvs]# curl 172.25.1.100

www.westos.org-server2

从 MAC 地址可以看出走的是 test4。
将 test1 的 keepalived 开启,并 test3 的 http 服务关掉,则客户只能访问 test2 的

[root@test3 ~]# /etc/init.d/httpd stop
[root@foundation1 lvs]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 lvs]# curl 172.25.1.100

www.westos.org-server2

[root@foundation1 lvs]# curl 172.25.1.100

www.westos.org-server2

若将两个都挂掉,则 test1,则客户端直接不能正常访问,与 ldirectord 不同的是本地 test1
不会接替让 VS 访问

[root@foundation1 lvs]# curl 172.25.1.100
curl: (7) Failed connect to 172.25.1.100:80; Connection refused
[root@foundation1 lvs]# curl 172.25.1.100
curl: (7) Failed connect to 172.25.1.100:80; Connection refused
[root@foundation1 lvs]# curl 172.25.1.100
curl: (7) Failed connect to 172.25.1.100:80; Connection refused