1. weight 大于0
如果脚本监测失败，优先级不变，如果成功，优先级增加，如果后续监测失败，则优先级在增加的基础上回退，这个weight不会持续增加或减小，只会存在两个值
2. weight 小于0
如果脚本监测失败，优先级降低，如果成功，优先级不变，这个weight不会持续增加或减小，只会存在两个值
另外，keepalived启动时，不论rise和fall的设置的是多少，首次监测脚本，都会根据上面的原则调整，后续的调整则要只有在进入fall和rise到达之后才会调整
The default weight equals 0, which means that any VRRP instance moni-
toring the script will transition to the fault state after
consecutive failures of the script. After that,consecu-
tive successes will cause VRRP instances to leave the fault state,
unless they are also in the fault state due to other scripts or inter-
faces that they are tracking.
A positive weight means thatsuccesses will add
to the priority of all VRRP instances which monitor it.
On the opposite, a negative weight will be subtracted from the initial
priority in case offailures.
