Keepalived双主模型中vrrp_script中权重改变故障排查

ispsh

故障重现
keepalived配置如下
# vi /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
root@localhost
}
notification_email_from admin@lnmmp.com
smtp_connect_timeout 3
smtp_server 127.0.0.1
router_id LVS_DEVEL
}
vrrp_script chk_maintaince_down {
script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"
interval 1
weight 2
}
vrrp_script chk_haproxy {
script "killall -0 haproxy"
interval 1
weight 2
}
vrrp_instance VI_1 {
interface eth0
state MASTER
priority 100
virtual_router_id 125
garp_master_delay 1
authentication {
auth_type PASS
auth_pass 1e3459f77aba4ded
}
track_interface {
eth0
}
virtual_ipaddress {
172.16.25.10/16 dev eth0 label eth0:0
}
track_script {
chk_haproxy
chk_maintaince_down
}
notify_master "/etc/keepalived/notify.sh master 172.16.25.10"
notify_backup "/etc/keepalived/notify.sh backup 172.16.25.10"
notify_fault "/etc/keepalived/notify.sh fault 172.16.25.10"
}
vrrp_instance VI_2 {
interface eth0
state BACKUP
priority 99
virtual_router_id 126
garp_master_delay 1
authentication {
auth_type PASS
auth_pass 7615c4b7f518cede
}
track_interface {
eth0
}
virtual_ipaddress {
172.16.25.11/16 dev eth0 label eth0:1
}
track_script {
chk_haproxy
chk_maintaince_down
}
notify_master "/etc/keepalived/notify.sh master 172.16.25.11"
notify_backup "/etc/keepalived/notify.sh backup 172.16.25.11"
notify_fault "/etc/keepalived/notify.sh fault 172.16.25.11"
}
# vi /etc/keepalived/notify.sh
#!/bin/bash
# Author: Jason.Yu
# description: An example of notify script
#
contact='root@localhost'
notify() {
mailsubject="`hostname` to be $1: $2 floating"
mailbody="`date '+%F %H:%M:%S'`: vrrp transition, `hostname` changed to be $1"
echo $mailbody | mail -s "$mailsubject" $contact
}
case "$1" in
master)
notify master $2
/etc/rc.d/init.d/haproxy start
exit 0
;;
backup)
notify backup $2
/etc/rc.d/init.d/haproxy stop
exit 0
;;
fault)
notify fault $2
/etc/rc.d/init.d/haproxy stop
exit 0
;;
*)
echo 'Usage: `basename $0` {master|backup|fault}'
exit 1
;;
esac引发的故障1：keepalived宕机恢复后VIP集体漂移故障

引发的故障2：haproxy服务停止后重启VIP集体漂移故障





原因
每次主备状态切换时，会引发notify_backup，而在notify.sh脚本中backup部分会执行/etc/rc.d/init.d/haproxy stop，导致权重在2个节点上都改变一次，从而单一节点上对于所有instance的权重都处于最大或者最小，故VIP集体漂移也就不奇怪了；




解决方法
修改notify.sh脚本，在处理backup部分，只发送通知邮件，而无需刻意停止haproxy服务；
# vi /etc/keepalived/notify.sh
#!/bin/bash
# Author: Jason.Yu
# description: An example of notify script
#
contact='root@localhost'
notify() {
mailsubject="`hostname` to be $1: $2 floating"
mailbody="`date '+%F %H:%M:%S'`: vrrp transition, `hostname` changed to be $1"
echo $mailbody | mail -s "$mailsubject" $contact
}
case "$1" in
master)
notify master $2
/etc/rc.d/init.d/haproxy start
exit 0
;;
backup)
notify backup $2
# /etc/rc.d/init.d/haproxy stop # 注释掉或删除此行
exit 0
;;
fault)
notify fault $2
# /etc/rc.d/init.d/haproxy stop # 同上
exit 0
;;
*)
echo 'Usage: `basename $0` {master|backup|fault}'
exit 1
;;
esac

调整后的正常权重改变流程



vrrp_script中节点权重改变算法
vrrp_script 里的script返回值为0时认为检测成功，其它值都会当成检测失败；

• weight 为正时，脚本检测成功时此weight会加到priority上，检测失败时不加；
  
  
  
  • 主失败:
    
    
    
    • 主 priority < 从 priority + weight 时会切换。
      
    
    
  • 主成功：
    
    
    
    • 主 priority + weight > 从 priority + weight 时，主依然为主
      
    
    
  
  
• weight 为负时，脚本检测成功时此weight不影响priority，检测失败时priority – abs(weight)
  
  
  
  • 主失败:
    
    
    
    • 主 priority – abs(weight) < 从priority 时会切换主从
      
    
    
  • 主成功:
    
    
    
    • 主 priority > 从priority 主依然为主