【Keepalived】抢占模式、延迟抢占模式与非抢占模式详解

本篇博客将介绍Keepalived抢占模式、延迟抢占模式还有非抢占模式的配置流程以及运行的效果,通过本篇博客你可以理解Keepalived的三个模式的配置和使用

环境:

系统:RHEL9.3

Keepalived版本:Keepalived v2.2.8 (04/04,2023)

主机名及IP:

  • KA1,172.25.254.50/24
  • KA2,172.25.254.60/24

1、三种模式的简介

  • 默认为抢占模式preempt,即当高优先级的主机恢复在线后,会抢占低先级的主机的master角色,这样会使vip在KA主机中来回漂移,造成网络抖动,

  • 建议设置为非抢占模式 nopreempt ,即高优先级主机恢复后,并不会抢占低优先级主机的master角色

  • 非抢占模块下,如果原主机down机, VIP迁移至的新主机, 后续也发生down时,仍会将VIP迁移回原主机

2、非抢占模式配置及效果

  • 编辑配置文件
cpp 复制代码
# 编辑KA1子配置文件
[root@KA1 ~]# vim /etc/keepalived/conf.d/WEB_VIP.conf 

vrrp_instance WEB_VIP {
    state BACKUP		# 注意:非抢占模式下主机互为BACKUP
    interface eth0
    virtual_router_id 51
    nopreempt			# 添加该参数,启用非抢占模式
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        172.25.254.100/24 dev eth0 label eth0:0
    }
}

# 重启服务
[root@KA1 ~]# systemctl restart keepalived.service
cpp 复制代码
# 编辑KA2子配置文件
[root@KA2 ~]# vim /etc/keepalived/conf.d/WEB_VIP.conf

vrrp_instance WEB_VIP {
    state BACKUP
    interface eth0
    virtual_router_id 51
    nopreempt
    priority 80
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        172.25.254.100/24 dev eth0 label eth0:0
    }
}

# 重启服务
[root@KA2 ~]# systemctl restart keepalived.service
  • 测试
cpp 复制代码
# 关闭master的服务
[root@KA1 ~]# systemctl stop keepalived.service 

# 查看KA2的VIP情况,可见VIP已经漂移到KA2
[root@KA2 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    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
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:81:44:a2 brd ff:ff:ff:ff:ff:ff
    altname enp3s0
    altname ens160
    inet 172.25.254.60/24 brd 172.25.254.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet 172.25.254.100/24 scope global secondary eth0:0
       valid_lft forever preferred_lft forever
    inet6 fe80::47bf:3a19:f4d5:a851/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

# 开启KA1的服务
[root@KA1 ~]# systemctl start keepalived.service

# 再查看KA2的VIP
# 可见KA2虽然优先级低,但是VIP还在
[root@KA2 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    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
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:81:44:a2 brd ff:ff:ff:ff:ff:ff
    altname enp3s0
    altname ens160
    inet 172.25.254.60/24 brd 172.25.254.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet 172.25.254.100/24 scope global secondary eth0:0
       valid_lft forever preferred_lft forever
    inet6 fe80::47bf:3a19:f4d5:a851/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

可见非抢占模式下不论优先级,只要主机不挂,VIP都不会漂移

3、延迟抢占模式配置及效果

抢占延迟模式,即优先级高的主机恢复后,不会立即抢回VIP,而是延迟一段时间(默认300s)再抢回VIP

cpp 复制代码
preempt_delay #     #指定抢占延迟时间为#s,默认延迟300s
  • 编辑配置文件
cpp 复制代码
# 编辑KA1子配置文件
[root@KA1 ~]# vim /etc/keepalived/conf.d/WEB_VIP.conf 

vrrp_instance WEB_VIP {
    state BACKUP
    interface eth0
    virtual_router_id 51
    preempt_delay 10		# 配置延迟时间为10s,方便观察
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        172.25.254.100/24 dev eth0 label eth0:0
    }
}

# 重启服务
[root@KA1 ~]# systemctl restart keepalived.service
cpp 复制代码
# 编辑KA2子配置文件
[root@KA2 ~]# vim /etc/keepalived/conf.d/WEB_VIP.conf

vrrp_instance WEB_VIP {
    state BACKUP
    interface eth0
    virtual_router_id 51
    preempt_delay 10
    priority 80
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        172.25.254.100/24 dev eth0 label eth0:0
    }
}

# 重启服务
[root@KA2 ~]# systemctl restart keepalived.service
  • 测试
cpp 复制代码
# 关闭KA1服务
[root@KA1 ~]# systemctl stop keepalived.service

# 查看VIP漂移情况
# 可见VIP到了KA2
[root@KA2 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    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
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:81:44:a2 brd ff:ff:ff:ff:ff:ff
    altname enp3s0
    altname ens160
    inet 172.25.254.60/24 brd 172.25.254.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet 172.25.254.100/24 scope global secondary eth0:0
       valid_lft forever preferred_lft forever
    inet6 fe80::47bf:3a19:f4d5:a851/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

# 开启KA1服务后马上查看KA2的VIP
# 可见当前VIP还在KA2上
[root@KA1 ~]# systemctl start keepalived.service
[root@KA2 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    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
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:81:44:a2 brd ff:ff:ff:ff:ff:ff
    altname enp3s0
    altname ens160
    inet 172.25.254.60/24 brd 172.25.254.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet 172.25.254.100/24 scope global secondary eth0:0
       valid_lft forever preferred_lft forever
    inet6 fe80::47bf:3a19:f4d5:a851/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever


# 等待10s后查看KA1VIP情况
# 可见VIP又回到了KA1上
[root@KA1 ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    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
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:93:eb:8f brd ff:ff:ff:ff:ff:ff
    altname enp3s0
    altname ens160
    inet 172.25.254.50/24 brd 172.25.254.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet 172.25.254.100/24 scope global secondary eth0:0
       valid_lft forever preferred_lft forever
    inet6 fe80::e3b4:c2e9:dca7:2b9b/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

可见在延迟抢占模式下会优先级高的主机会等待设定的时间结束后才枪占VIP

至此实验全部结束

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