2.抢占模式和非抢占模式-摩杜云开发者社区

非抢占式模式

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,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

注意: 非抢占模式下,如果原主机down机, VIP迁移至的新主机,后续新主机也发生down时,VIP还会迁移回 修复好的原主机

但如果新主机的服务down掉(keepalived服务正常),原主机也不会接管VIP,仍会由新主机拥有VIP即非抢占式模式,只是适合当主节点宕机,切换到从节点的一次性的高可用性,后续即使当原主节点修复好,仍无法再次起到高用功能

注意：要关闭 VIP抢占,必须将各 Keepalived 服务器 state 配置为 BACKUP

非抢占式配置

节点一：
vrrp_instance VI_1 {
    state BACKUP             #都为BACKUP	
    interface eth1
    virtual_router_id 66
    priority 100             #优先级高
    advert_int 1
    nopreempt                #添加此行设为nopreempt
    
节点二：  
vrrp_instance VI_1 {
    state BACKUP             #都为BACKUP	
    interface eth1
    virtual_router_id 66
    priority 80              #优先级低
    advert_int 1
    nopreempt                #添加此行设为nopreempt
    
所有节点重启keepalived

挂掉节点一，观察结果

[root@ubuntu2004 ~]#tcpdump -i eth1 -nn host 224.0.0.18
23:09:59.835993 IP 192.168.10.100 > 224.0.0.18: VRRPv2, Advertisement, vrid 66, prio 100, authtype simple, intvl 1s, length 20
23:10:00.687778 IP 192.168.10.100 > 224.0.0.18: VRRPv2, Advertisement, vrid 66, prio 0, authtype simple, intvl 1s, length 20
23:10:01.376464 IP 192.168.10.101 > 224.0.0.18: VRRPv2, Advertisement, vrid 66, prio 80, authtype simple, intvl 1s, length 20
节点二接替节点一组播地址信息
[root@ubuntu2004 ~]#hostname -I
10.0.0.102 10.0.0.100 192.168.10.101
VIP地址飘到了节点二上

节点一重启后，观察结果

主节点二IP
[root@ubuntu2004 ~]#hostname -I
10.0.0.102 10.0.0.100 192.168.10.101

节点二依然在组播地址信息
[root@ubuntu2004 ~]#tcpdump -i eth1 -nn host 224.0.0.18
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 262144 bytes
23:13:23.538298 IP 192.168.10.101 > 224.0.0.18: VRRPv2, Advertisement, vrid 66, prio 80, authtype simple, intvl 1s, length 20
23:13:24.539440 IP 192.168.10.101 > 224.0.0.18: VRRPv2, Advertisement, vrid 66, prio 80, authtype simple, intvl 1s, length 20

挂掉节点二，观察结果

回到节点一组播地址信息
[root@ubuntu2004 ~]#tcpdump -i eth1 -nn host 224.0.0.18
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 262144 bytes
23:14:41.199520 IP 192.168.10.100 > 224.0.0.18: VRRPv2, Advertisement, vrid 66, prio 100, authtype simple, intvl 1s, length 20
查看节点一IP信息
[root@ubuntu2004 ~]#hostname -I
10.0.0.101 10.0.0.100 192.168.10.100
查看节点二IP信息
[root@ubuntu2004 ~]#hostname -I
10.0.0.102 192.168.10.101

抢占延迟模式preempt_delay

抢占延迟模式，即优先级高的主机恢复后，不会立即抢回VIP，而是延迟一段时间在抢回VIP
preempt_delay    #指定抢占延迟时间为#s,默认延迟300s

节点一：
vrrp_instance VI_1 {
    state BACKUP             #都为BACKUP	
    interface eth1
    virtual_router_id 66
    priority 100             #优先级高
    advert_int 1
    preempt_delay 60         #抢占延迟模式，默认延迟300s
    
节点二：  
vrrp_instance VI_1 {
    state BACKUP             #都为BACKUP	
    interface eth1
    virtual_router_id 66
    priority 80             #优先级低
    advert_int 1

VIP 单播配置

单播的优点
1、默认keepalived主机之间利用多播相互通告消息,会造成网络拥塞,可以替换成单播,减少网络流量
2、点对点，比较安全
3、在全局配置里面配置多播
vrrp_mcast_group4 239.0.0.0 #单播优于多播


（多播地址范围为D类地址）
A类：1-126
B类：128-191
C类：192-223
D类：224-239
E类：240-254
另外：有些公有云不支持多播,可以单播实现 
注意：启用 vrrp_strict 时,不能启用单播

配置如下：

节点一
[root@ubuntu2004 ~]#vim /etc/keepalived/conf.d/www.meng.org.conf
vrrp_instance VI_1 {
    state BACKUP
    interface eth1
    virtual_router_id 66
    priority 100
    advert_int 1
    #nopreempt
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
    10.0.0.100/24 dev eth0 label eth0:1
    }
    unicast_src_ip 192.168.10.100              #指定发送单播的源IP，心跳线地址
    unicast_peer{
        192.168.10.101                         #其他节点单播接收地址，也是心跳线地址
  }
}
[root@ubuntu2004 ~]#systemctl restart keepalived.service

节点二：
[root@ubuntu2004 ~]#vim /etc/keepalived/conf.d/www.meng.org.conf 
vrrp_instance VI_1 {
    state BACKUP
    interface eth1
    virtual_router_id 66
    priority 80
    advert_int 1
    #nopreempt
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
    10.0.0.100/24 dev eth0 label eth0:1
  }
    unicast_src_ip 192.168.10.101                #指定发送单播的源IP，心跳线地址
    unicast_peer{
        192.168.10.100                           #其他节点单播接收地址，也是心跳线地址
  }
}
[root@ubuntu2004 ~]#systemctl restart keepalived.service

单播抓包 tcpdump -i eth1 -nn host 192.168.10.100

停止节点一服务，查看节点二IP
[root@ubuntu2004 ~]#systemctl stop keepalived.service
[root@ubuntu2004 ~]#hostname -I
10.0.0.102 10.0.0.100 192.168.10.101

Keepalived 通知脚本配置

当keepalived的状态变化时,可以自动触发脚本的执行,比如：发邮件通知用户

默认以用户keepalived_script身份执行脚本,如果此用户不存在,以root执行脚本

通知脚本类型

当前节点成为主节点时触发的脚本

notify_master <STRING>|<QUOTED-STRING>

当前节点转为备节点时触发的脚本

notify_backup <STRING>|<QUOTED-STRING>

当前节点转为“失败”状态时触发的脚本

notify_fault <STRING>|<QUOTED-STRING>

通用格式的通知触发机制,一个脚本可完成以上三种状态的转换时的通知

notify <STRING>|<QUOTED-STRING>

当停止VRRP时触发的脚本

notify_stop <STRING>|<QUOTED-STRING>

ubuntu通过send email命令往外发邮件（根据三种不同的状态发送邮件master|backup|fault）

发邮件脚本
[root@ubuntu2004 ~]#cat notify.sh 
#!/bin/bash
contact='13298188777@163.com'         #接收邮件帐号
email_send='1153454651@qq.com'        #发邮件帐号
email_passwd='bdeuidngbzvufjjf'       #发邮件帐号授权码
email_smtp_server='smtp.qq.com'

. /etc/os-release

msg_error() {
  echo -e "\033[1;31m$1\033[0m"
}

msg_info() {
  echo -e "\033[1;32m$1\033[0m"
}

msg_warn() {
  echo -e "\033[1;33m$1\033[0m"
}

color () {
    RES_COL=60
    MOVE_TO_COL="echo -en \\033[${RES_COL}G"
    SETCOLOR_SUCCESS="echo -en \\033[1;32m"
    SETCOLOR_FAILURE="echo -en \\033[1;31m"
    SETCOLOR_WARNING="echo -en \\033[1;33m"
    SETCOLOR_NORMAL="echo -en \E[0m"
    echo -n "$1" && $MOVE_TO_COL
    echo -n "["
    if [ $2 = "success" -o $2 = "0" ] ;then
        ${SETCOLOR_SUCCESS}
        echo -n $"  OK  "    
    elif [ $2 = "failure" -o $2 = "1"  ] ;then 
        ${SETCOLOR_FAILURE}
        echo -n $"FAILED"
    else
        ${SETCOLOR_WARNING}
        echo -n $"WARNING"
    fi
    ${SETCOLOR_NORMAL}
    echo -n "]"
    echo 
}


install_sendemail () {
    if [[ $ID =~ rhel|centos|rocky ]];then
        rpm -q sendemail &> /dev/null ||  yum install -y sendemail
    elif [ $ID = 'ubuntu' ];then
        dpkg -l |grep -q sendemail  || { apt update; apt install -y libio-socket-ssl-perl libnet-ssleay-perl sendemail ; } 
    else
        color "不支持此操作系统，退出!" 1
        exit
    fi
}

send_email () {
    local email_receive="$1"
    local email_subject="$2"
    local email_message="$3"
    sendemail -f $email_send -t $email_receive -u $email_subject -m $email_message -s $email_smtp_server -o message-charset=utf-8 -o tls=yes -xu $email_send -xp $email_passwd
    [ $? -eq 0 ] && color "邮件发送成功!" 0 || color "邮件发送失败!" 1 
}

notify() {
    if [[ $1 =~ ^(master|backup|fault)$ ]];then
        mailsubject="$(hostname) to be $1, vip floating"
        mailbody="$(date +'%F %T'): vrrp transition, $(hostname) changed to be $1"
        send_email "$contact" "$mailsubject" "$mailbody"
   else
        echo "Usage: $(basename $0) {master|backup|fault}"
        exit 1
   fi
}

install_sendemail 
notify $1

给脚本加执行权限并测试

[root@ubuntu2004 ~]#chmod +x notify.sh
[root@ubuntu2004 ~]#./notify.sh master
可观察到发送的邮件
[root@ubuntu2004 ~]#./notify.sh backup
[root@ubuntu2004 ~]#./notify.sh fault

脚本调用方法

在 vrrp_instance VI_1 语句块的末尾加下面行
notify_master "/etc/keepalived/notify.sh master" 
notify_backup "/etc/keepalived/notify.sh backup"  
notify_fault "/etc/keepalived/notify.sh fault"

范例

各节点配置脚本调用方法（都配置）
[root@ubuntu2004 ~]#vim /etc/keepalived/conf.d/www.meng.org.conf
vrrp_instance VI_1 {
    state BACKUP
    interface eth1
    virtual_router_id 66
    priority 100
    advert_int 1
    #nopreempt
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
    10.0.0.100/24 dev eth0 label eth0:1
    }
    unicast_src_ip 192.168.10.100
    unicast_peer{
        192.168.10.101
  }
notify_master "/etc/keepalived/notify.sh master"  #当节点的状态称为master就会发送邮件
notify_backup "/etc/keepalived/notify.sh backup"  #当节点的状态称为backup就会发送邮件
notify_fault "/etc/keepalived/notify.sh fault"    #当节点的状态称为fault就会发送邮件
}
把脚本移动到/etc/keepalived/路径下
[root@ubuntu2004 ~]#ll /etc/keepalived/notify.sh 
-rwxr-xr-x 1 root root 2431 10月 29 14:33 /etc/keepalived/notify.sh*
重启
[root@ubuntu2004 ~]#systemctl restart keepalived.service
最好把两个节点区别开来，容易辨别哪个节点发送的邮件，可更改主机名

测试邮件性能

目前VIP地址存放节点在ka1，停掉ka1节点keepalived服务，ka2节点状态变了，会发送邮件
[root@ka2 ~]#hostname -I
10.0.0.102 10.0.0.100 192.168.10.101
收到ka2节点发送的邮件（邮件内容如下）
2022-10-29 14:54:05: vrrp transition, ka2 changed to be master

重启ka1节点，由于是抢占式状态，ka1节点会抢占VIP,并且收到三份邮件
[root@ka1 ~]#systemctl start keepalived
[root@ka1 ~]#hostname -I
10.0.0.101 10.0.0.100 192.168.10.100

收到三份邮件
第一份是ka1起来后，还未抢占VIP发送的状态邮件
2022-10-29 14:56:23: vrrp transition, ka1 changed to be backup
第二份是ka2被抢占VIP后发送的状态邮件
2022-10-29 14:56:26: vrrp transition, ka2 changed to be backup
第三份是ka1抢占VIP后发送的状态邮件
2022-10-29 14:56:26: vrrp transition, ka1 changed to be master