Keepalived主要用于实现LVS负载均衡和系统服务的高可用，借助VRRP协议进行故障切换。当主节点故障时，备节点接管IP资源，确保业务连续性。本文介绍了Keepalived的重要功能、VRRP协议以及部署步骤。
keepalived简介
Keepalived 软件起初是专为LVS负载均衡软件设计的，用来管理并监控LVS集群系统中各个服务节点的状态，后来又加入了可以实现高可用的VRRP功能。因此，Keepalived除了能够管理LVS软件外，还可以作为其他服务（例如：Nginx、Haproxy、MySQL等）的高可用解决方案软件。
Keepalived软件主要是通过VRRP协议实现高可用功能的。VRRP是Virtual Router RedundancyProtocol(虚拟路由器冗余协议）的缩写，VRRP出现的目的就是为了解决静态路由单点故障问题的，它能够保证当个别节点宕机时，整个网络可以不间断地运行。
所以，Keepalived 一方面具有配置管理LVS的功能，同时还具有对LVS下面节点进行健康检查的功能，另一方面也可实现系统网络服务的高可用功能。
Keepalived官网
Keepalived的重要功能
keepalived 有三个重要的功能，分别是：
（1）管理LVS负载均衡软件
（2）实现LVS集群节点的健康检查
（3）作为系统网络服务的高可用性
3、keepalived高可用故障转移的原理
Keepalived 高可用服务之间的故障切换转移，是通过 VRRP (Virtual Router Redundancy Protocol ,虚拟路由器冗余协议）来实现的。
在 Keepalived 服务正常工作时，主 Master 节点会不断地向备节点发送（多播的方式）心跳消息，用以告诉备 Backup 节点自己还活看，当主 Master 节点发生故障时，就无法发送心跳消息，备节点也就因此无法继续检测到来自主 Master 节点的心跳了，于是调用自身的接管程序，接管主 Master 节点的 IP 资源及服务。而当主 Master 节点恢复时，备 Backup 节点又会释放主节点故障时自身接管的IP资源及服务，恢复到原来的备用角色。
keepalived原理
Keepalived高可用对之间是通过VRRP通信的，因此，我们从 VRRP开始了解起：
（1） VRRP,全称 Virtual Router Redundancy Protocol,中文名为虚拟路由冗余协议，VRRP的出现是为了解决静态路由的单点故障。
（2）VRRP是通过一种竟选协议机制来将路由任务交给某台 VRRP路由器的。
（3）VRRP用 IP多播的方式（默认多播地址（224.0.0.18))实现高可用对之间通信。
（4）工作时主节点发包，备节点接包，当备节点接收不到主节点发的数据包的时候，就启动接管程序接管主节点的资源。备节点可以有多个，通过优先级竞选，但一般 Keepalived系统运维工作中都是一对。
（5）VRRP使用了加密协议加密数据，但Keepalived官方目前还是推荐用明文的方式配置认证类型和密码。
介绍完 VRRP,接下来我再介绍一下 Keepalived服务的工作原理：
Keepalived高可用是通过 VRRP 进行通信的， VRRP是通过竞选机制来确定主备的，主的优先级高于备，因此，工作时主会优先获得所有的资源，备节点处于等待状态，当主挂了的时候，备节点就会接管主节点的资源，然后顶替主节点对外提供服务。
在 Keepalived 服务之间，只有作为主的服务器会一直发送 VRRP 广播包,告诉备它还活着，此时备不会枪占主，当主不可用时，即备监听不到主发送的广播包时，就会启动相关服务接管资源，保证业务的连续性.接管速度最快可以小于1秒。
keepalived部署
| 主机名 | IP | 系统 |
|---|---|---|
| Master | IP:192.168.40.99 --VIP: 192.168.40.111 | rhel8/centos8 |
| Slave | IP:192.168.40.100 | rhel8/centos8 |
Master主节点和slave备份节点
关闭防火墙和selinux
systemctl stop firewalld
systemctl disable firewalld
cat /etc/sysconfig/selinux
SELINUX=disabled
配置yum源--阿里源centos8和epel源
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-vault-8.5.2111.repo
yum install -y https://mirrors.aliyun.com/epel/epel-release-latest-8.noarch.rpm
sed -i 's|^#baseurl=https://download.example/pub|baseurl=https://mirrors.aliyun.com|' /etc/yum.repos.d/epel*
sed -i 's|^metalink|#metalink|' /etc/yum.repos.d/epel*
安装一下常用命令
dnf -y install gcc gcc-c++
安装keepalived
dnf -y install keepalived
在master节点安装nginx
[root@Master ~]# dnf -y install nginx
[root@Master ~]# systemctl restart nginx.service
[root@Master ~]# systemctl enable nginx.service
Created symlink /etc/systemd/system/multi-user.target.wants/nginx.service → /usr/lib/systemd/system/nginx.service.
在nginx中添加测试网页
[root@Master ~]# cd /usr/share/nginx/html/
[root@Master html]# ls
404.html 50x.html index.html nginx-logo.png poweredby.png
[root@Master html]# echo 'hi Master' > index.html
在slave节点安装nginx
[root@Slave ~]# systemctl restart nginx.service
[root@Slave ~]# systemctl enable nginx.service
Created symlink /etc/systemd/system/multi-user.target.wants/nginx.service → /usr/lib/systemd/system/nginx.service.
[root@Slave ~]# dnf -y install nginx
在nginx中添加测试网页
[root@Slave ~]# cd /usr/share/nginx/html/
[root@Slave html]# ls
404.html 50x.html index.html nginx-logo.png poweredby.png
[root@Slave html]# echo "hi Slave" > index.html
配置主keepalived
例子：
at keepalived.conf //查看配置文件
! Configuration File for keepalived
global_defs { //全局配置
notification_email { //定义报警收件人邮件地址
acassen@firewall.loc
failover@firewall.loc
sysadmin@firewall.loc
}
notification_email_from Alexandre.Cassen@firewall.loc //定义报警发件人邮箱
smtp_server 192.168.200.1 //邮箱服务器地址
smtp_connect_timeout 30 //定义邮箱超时时间
router_id LVS_DEVEL //定义路由标识信息，同局域网内唯一
vrrp_skip_check_adv_addr
vrrp_strict
vrrp_garp_interval 0
vrrp_gna_interval 0
}
vrrp_instance VI_1 { //定义实例
state MASTER //指定keepalived节点的初始状态，可选值为MASTER/BACKUP
interface eth0 //VRRP实例绑定的网卡接口，用户发送VRRP包
virtual_router_id 51 //虚拟路由的ID，同一集群要一致
priority 100 //定义优先级，按优先级来决定主备角色，优先级越大越优先
advert_int 1 //主备通讯时间间隔
authentication { //配置认证
auth_type PASS //认证方式，此处为密码
auth_pass 1111 //同一集群中的keepalived配置里此处必须一致，推荐使用8为随机数
}
virtual_ipaddress { //配置要使用的VIP
192.168.200.16
192.168.200.17
192.168.200.18
}
}
virtual_server 192.168.200.100 443 { //配置虚拟服务器
delay_loop 6 //健康检查的时间间隔
lb_algo rr //lvs调度算法
lb_kind NAT //lvs模式
persistence_timeout 50 //持久化超时时间，单位为秒
protocol TCP //4层协议
sorry_server 192.168.200.200 1358 //定义备用服务器，当所有RS都故障时，用sorry_server来响应客户端
real_server 192.168.201.100 443 { //定义真是处理请求的服务器
weight 1 //给服务器指定权重，默认为1
SSL_GET {
url {
path / //指定要检查的URL路径
digest ff20ad2481f97b1754ef3e12ecd3a9cc //摘要信息
}
url {
path /mrtg/
digest 9b3a0c85a887a256d6939da88aabd8cd
}
connect_timeout 3 //连接超时时间
retry 3 //get尝试次数
delay_before_retry 3 //在尝试之前延迟多长时间
}
}
}
real_server 192.168.100.100 80 {
weight 1
TCP_CHECK {
connect_port 80 //连接端口
connect_timeout 3 //连接超时时间，默认为5秒
nb_get_retry 3
delay_before_retry 3 //在重试之前延迟多少秒
[root@Master ~]# cd /etc/keepalived/
[root@Master keepalived]# cp keepalived.conf keepalived.conf.bak
[root@Master keepalived]# vim keepalived.conf
! Configuration File for keepalived
global_defs {
router_id haha
}
vrrp_instance VI_1 {
state MASTER
interface ens33
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.40.111
}
}
virtual_server 192.168.40.111 80 {
delay_loop 6
lb_algo rr
lb_kind DR
persistence_timeout 50
protocol TCP
real_server 192.168.40.99 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
real_server 192.168.40.100 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
重启服务并设置下次启动生效
[root@Master keepalived]# systemctl restart keepalived.service
[root@Master keepalived]# systemctl enable keepalived.service
Created symlink /etc/systemd/system/multi-user.target.wants/keepalived.service → /usr/lib/systemd/system/keepalived.service.
在slave节点配置备份keepalived
[root@Slave ~]# cd /etc/keepalived/
[root@Slave keepalived]# cp keepalived.conf keepalived.conf.bak
[root@Slave keepalived]# vim keepalived.conf
! Configuration File for keepalived
global_defs {
router_id hehe
}
vrrp_instance VI_1 {
state BACKUP
interface ens33
virtual_router_id 51
priority 90
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.40.111
}
}
virtual_server 192.168.40.111 80 {
delay_loop 6
lb_algo rr
lb_kind DR
persistence_timeout 50
protocol TCP
real_server 192.168.40.99 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
real_server 192.168.40.100 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
重启服务并设置下次启动生效
[root@Slave keepalived]# systemctl restart keepalived.service
[root@Slave keepalived]# systemctl enable keepalived.service
Created symlink /etc/systemd/system/multi-user.target.wants/keepalived.service → /usr/lib/systemd/system/keepalived.service.
在master中配置VIP
[root@Master ~]# ip addr add 192.168.40.111/32 dev ens33
root@Master ~]# ip addr show ens33
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:0c:29:a3:51:0a brd ff:ff:ff:ff:ff:ff
inet 192.168.40.99/24 brd 192.168.40.255 scope global noprefixroute ens33
valid_lft forever preferred_lft forever
inet 192.168.40.111/32 scope global ens33
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fea3:510a/64 scope link noprefixroute
valid_lft forever preferred_lft forever
修改内核参数，开启侦听VIP功能
此步可做可不做，该功能可用于仅监听VIP的时候
Master和slave
vim /etc/sysctl.conf
net.ipv4.ip_nonlocal_bind = 1
sysctl -p
net.ipv4.ip_nonlocal_bind = 1
让keepalived监控nginx负载均衡
在master上编写脚本
[root@Master ~]# mkdir /scripts
[root@Master ~]# cd /scripts/
[root@Master scripts]# vim check.sh
[root@Master scripts]# cat check.sh
#!/bin/bash
nginx_status=`ps -ef | grep -v "grep" | grep "nginx" | wc -l`
if [ $nginx_status -lt 1 ];then
systemctl stop keepalived
fi
[root@Master scripts]# chmod +x check.sh
[root@Master scripts]# vim notify.sh
[root@Master scripts]# cat notify.sh
#!/bin/bash
VIP=$2
sendmail () {
subject="${VIP}'s server keepalived state is translate"
content="`date +'%F %T'`: `hostname`'s state change to master"
echo $content | mail -s "$subject" haha@example.com
}
case "$1" in
master)
nginx_status=$(ps -ef|grep -Ev "grep|$0"|grep '\bnginx\b'|wc -l)
if [ $nginx_status -lt 1 ];then
systemctl start nginx
fi
sendmail
;;
backup)
nginx_status=$(ps -ef|grep -Ev "grep|$0"|grep '\bnginx\b'|wc -l)
if [ $nginx_status -gt 0 ];then
systemctl stop nginx
fi
;;
*)
echo "Usage:$0 master|backup VIP"
;;
esac
[root@Master scripts]# chmod +x notify.sh
在slave上编写脚本
[root@Slave ~]# mkdir /scripts
[root@Slave ~]# cd /scripts/
[root@Slave scripts]# scp -r root@192.168.40.99:/scripts/* .
root@192.168.40.99's password:
check.sh 100% 144 198.3KB/s 00:00
notify.sh 100% 595 914.7KB/s 00:00
[root@Slave scripts]# ll
总用量 8
-rwxr-xr-x. 1 root root 144 10月 8 01:18 check.sh
-rwxr-xr-x. 1 root root 595 10月 8 01:18 notify.sh
配置master的keepalived
[root@Master keepalived]# cat keepalived.conf
[root@Master keepalived]# cat keepalived.conf
! Configuration File for keepalived
global_defs {
router_id haha
}
vrrp_script nginx_check {
script "/scripts/check.sh"
interval 10
weight -20
}
vrrp_instance VI_1 {
state MASTER
interface ens33
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.40.111
}
track_script {
nginx_check
}
notify_master "/scripts/notify.sh master 192.168.40.111"
notify_backup "/scripts/notify.sh backup 192.168.40.111"
}
virtual_server 192.168.40.111 80 {
delay_loop 6
lb_algo rr
lb_kind DR
persistence_timeout 50
protocol TCP
real_server 192.168.40.99 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
real_server 192.168.40.100 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
[root@Master keepalived]# systemctl restart keepalived.service
配置slave的keepalived
[root@Slave keepalived]# cat keepalived.conf
! Configuration File for keepalived
global_defs {
router_id hehe
}
vrrp_instance VI_1 {
state BACKUP
interface ens33
virtual_router_id 51
priority 90
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.40.111
}
notify_master "/scripts/notify.sh master 192.168.40.111"
notify_backup "/scripts/notify.sh backup 192.168.40.111"
}
virtual_server 192.168.40.111 80 {
delay_loop 6
lb_algo rr
lb_kind DR
persistence_timeout 50
protocol TCP
real_server 192.168.40.99 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
real_server 192.168.40.100 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
[root@Slave keepalived]# systemctl restart keepalived.service
模拟故障
启用keepalived，开启nginx服务
[root@Master ~]# systemctl restart keepalived.service
[root@Master ~]# systemctl enable keepalived.service
[root@Master ~]# systemctl restart nginx.service
[root@Master ~]# systemctl enable nginx.service
在slave中查看端口80是否开启
[root@Slave keepalived]# ss -antlp
State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
LISTEN 0 128 0.0.0.0:111 0.0.0.0:* users:(("rpcbind",pid=912,fd=4),("systemd",pid=1,fd=40))
LISTEN 0 32 192.168.122.1:53 0.0.0.0:* users:(("dnsmasq",pid=1816,fd=6))
LISTEN 0 128 0.0.0.0:22 0.0.0.0:* users:(("sshd",pid=1000,fd=4))
LISTEN 0 5 127.0.0.1:631 0.0.0.0:* users:(("cupsd",pid=1163,fd=10))
LISTEN 0 128 [::]:111 [::]:* users:(("rpcbind",pid=912,fd=6),("systemd",pid=1,fd=42))
LISTEN 0 128 [::]:22 [::]:* users:(("sshd",pid=1000,fd=6))
LISTEN 0 5 [::1]:631 [::]:* users:(("cupsd",pid=1163,fd=9))
关闭master的nginx服务
[root@Master scripts]# systemctl stop nginx
在slave中查看端口80是否开启
[root@Slave keepalived]# ss -antlp
State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
LISTEN 0 128 0.0.0.0:111 0.0.0.0:* users:(("rpcbind",pid=912,fd=4),("systemd",pid=1,fd=40))
LISTEN 0 128 0.0.0.0:80 0.0.0.0:* users:(("nginx",pid=2892,fd=8),("nginx",pid=2891,fd=8),("nginx",pid=2890,fd=8))
LISTEN 0 32 192.168.122.1:53 0.0.0.0:* users:(("dnsmasq",pid=1816,fd=6))
LISTEN 0 128 0.0.0.0:22 0.0.0.0:* users:(("sshd",pid=1000,fd=4))
LISTEN 0 5 127.0.0.1:631 0.0.0.0:* users:(("cupsd",pid=1163,fd=10))
LISTEN 0 128 [::]:111 [::]:* users:(("rpcbind",pid=912,fd=6),("systemd",pid=1,fd=42))
LISTEN 0 128 [::]:80 [::]:* users:(("nginx",pid=2892,fd=9),("nginx",pid=2891,fd=9),("nginx",pid=2890,fd=9))
LISTEN 0 128 [::]:22 [::]:* users:(("sshd",pid=1000,fd=6))
LISTEN 0 5 [::1]:631 [::]:* users:(("cupsd",pid=1163,fd=9))
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