Slide 9
Slide 9 text
Relative vs. Absolute
M e t r i c s ͷ ύ ϥ μ Π Ϝ γ ϑ τ
“We chose values of the target metric to be relative (e.g. 90% of requested CPU resource) rather than
absolute (e.g. 0.6 core) for the following reason. If we choose absolute metric, user will need to
guarantee that the target is lower than the request. Otherwise, overloaded pods may not be able to
consume more than the autoscaler's absolute target utilization, thereby preventing the autoscaler
from seeing high enough utilization to trigger it to scale up. This may be especially troublesome when
user changes requested resources for a pod because they would need to also change the autoscaler
utilization threshold. Therefore, we decided to choose relative metric. For user, it is enough to set it to a
value smaller than 100%, and further changes of requested resources will not invalidate it.”
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https://github.com/kubernetes/community/blob/1a65632090645379db59d0b5d77c502d171ae0ec/contributors/design-proposals/autoscaling/horizontal-pod-autoscaler.md#relative-vs-absolute-metrics