LVS+Keepalived realizes high-availability cluster framework construction

1. LVS+Keepalived high-availability cluster

LVS provides load balancing, keepalived provides health check, failover, and improves system availability! After adopting such an architecture, it is easy to extend the existing system, as long as the realserver is added or reduced in the backend, as long as the configuration file of lvs is changed, and seamless configuration changes can be realized!

1、LVS

Linux Virtual Server
LVS is actually equivalent to a virtualized application based on IP address, and proposes an efficient solution for load balancing based on IP address and content request distribution

2、Keepalived

Support automatic failover (Failover)
Support node health check (Health Checking)
Determine the availability of the LVS load scheduler and node server. When the master host fails, switch to the backup node in time to ensure normal business. When the master fails, it will rejoin the cluster and the business will be switched back to the master node.

3. Analysis of Keepalived Implementation Principle

Keepalived adopts VRRP hot backup protocol to realize the multi-machine hot backup function of Linux server
VRRP (Virtual Routing Redundancy Protocol) is a backup solution for routers.
Multiple routers form a hot backup group, and provide services to the outside through a shared virtual IP address
There is only one master router in each hot standby group to provide services at the same time, and other routers are in redundant state
If the currently online router fails, other routers will automatically take over the virtual IP address according to the set priority and continue to provide services

Two, Ipvsadm tool

Use options:
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Three, LVS+Keepalived architecture construction

Scheduler one IP: 192.168.90.10; scheduler two IP: 192.168.90.60

The configuration steps of the two schedulers are the same here

systemctl stop firewalld.service
setenforce 0

yum -y install ipvsadm keepalived
modprobe ip_vs            #加载ip_vs模块
cat /proc/net/ip_vs       #查看ip_vs版本  

vim /etc/sysctl.conf      #修改内核配置

net.ipv4.conf.all.send_redirects = 0          #以下三条为关闭重定向
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.ens33.send_redirects = 0

sysctl -p                 #加载配置参数

ipvsadm-save > /etc/sysconfig/ipvsadm
systemctl start ipvsadm

ipvsadm -C
ipvsadm -A -t 192.168.184.10:80 -s rr       #这里指定的虚拟IP为ens33网卡ip，重启keepliaved后会自动绑定虚拟网卡
ipvsadm -a -t 192.168.90.10:80 -r 192.168.90.20:80 -g
ipvsadm -a -t 192.168.90.10:80 -r 192.168.90.50:80 -g
ipvsadm

ipvsadm -ln

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NFS shared server (192.168.90.70)

systemctl stop firewalld.service
systemctl disable firewalld.service
setenforce 0

yum -y install nfs-utils rpcbind

systemctl start rpcbind.service
systemctl start nfs.service

systemctl enable nfs.service
systemctl enable rpcbind.service

mkdir /opt/lfp
mkdir /opt/accp

chmod 777 /opt/lfp
chmod 777 /opt/accp

vim /etc/exports
/opt/lfp 192.168.90.0/24(rw,sync)
/opt/accp 192.168.90.0/24(rw,sync)

exportfs -rv

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Configure node server

两台相同配置方法（192.168.90.20、192.168.90.50）

systemctl stop firewalld
setenforce 0

yum -y install httpd
systemctl start httpd

vim /etc/sysconfig/network-scripts/ifcfg-lo:0
DEVICE=lo:0
ONBOOT=yes
IPADDR=192.168.184.188
NETMASK=255.255.255.255

service network restart 或 systemctl restart network
ifup lo:0
ifconfig lo:0
route add -host 192.168.90.188 dev lo:0		#添加VIP本地访问路由，将访问VIP的数据限制在本地，以避免通信紊乱

vim /etc/sysctl.conf

net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.lo.arp_announce = 2
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2

sysctl -p

Web-1（192.168.90.20）

mount.nfs 192.168.90.70:/opt/lfp /var/www/html
echo 'this is lfp web!' > /var/www/html/index.html

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Web-2（192.168.90.50）

mount.nfs 192.168.90.70:/opt/accp /var/www/html
echo 'this is accp web!' > /var/www/html/index.html

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Configure keeplived (set on the primary and standby DR servers)

Configure on the scheduler server

cd /etc/keepalived/
cp keepalived.conf keepalived.conf.bak
vim keepalived.conf

global_defs {						#定义全局参数

10行修改，邮件服务指向本地
smtp_server 127.0.0.1

12行修改，指定服务器（路由器）的名称，主备服务器名称须不同，主为LVS_01，备为LVS_02
router_id LVS_01

14行修改，vrrp_strict：严格遵守VRRP协议。下列情况将会阻止启动Keepalived
1. 没有VIP地址。2. 单播邻居。3. 在VRRP版本2中有IPv6地址。
#vrrp_strict						#加注释
           
vrrp_instance VI_1 {				#定义VRRP热备实例参数

20行修改，指定热备状态，主为MASTER，备为BACKUP
state MASTER

21行修改，指定承载vip地址的物理接口
interface ens33

22行修改，指定虚拟路由器的ID号，每个热备组保持一致
virtual_router_id 10

23行修改，指定优先级，数值越大优先级越高，主为100，备为99
priority 100                    #优先级
advert_int 1					#通告间隔秒数(心跳频率)
authentication {				#定义认证信息,每个热备组保持一致
auth_type PASS				    #认证类型

27行修改，指定验证密码，主备服务器保持一致
auth_pass 123123

30行修改，群集vip地址
virtual_ipaddress {				#指定群集vip地址
192.168.90.188

34行修改，指定虚拟服务器地址(VIP)、端口，定义虚拟服务器和Web服务器池参数

virtual_server 192.168.90.188 80 {
delay_loop 6					#健康检查的间隔时间(秒)
lb_algo rr						#指定调度算法，轮询(rr)

37行修改，指定群集工作模式，直接路由(DR)
lb_kind DR
persistence_timeout 50			#连接保持时间(秒)
protocol TCP					#应用服务采用的是 TCP协议

41行修改，指定第一个Web节点的地址、端口
real_server 192.168.90.20 80 {
weight 1						#节点的权重

42行往下删除，添加以下健康检查方式
 TCP_CHECK {
		connect_port 80			#添加检查的目标端口
		connect_timeout 3		#添加连接超时(秒)
		nb_get_retry 3			#添加重试次数
		delay_before_retry 4	#添加重试间隔
	}
}

real_server 192.168.90.50 80 {		#添加第二个 Web节点的地址、端口
    weight 1
    TCP_CHECK {
		connect_port 80
		connect_timeout 3
		nb_get_retry 3
		delay_before_retry 4
	}
}
}

After saving and exiting

systemctl start keepalived
ip addr show dev ens33				#查看虚拟网卡vip

Client access to 192.169.90.188
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and refresh after a period of time:

turn off the main scheduling server ens33:0 network card, and verify again

ifdown ens33
ifconfig

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