Kubernetes dynamic configuration of CPU resource limit

Question

Kubernetes CPU manager provides a way to configure CPU resource limit statically. However, in some cases it could lead to a waste of cluster resources, for example an application could require significant CPU during its startup, later on allocated resources are not required anymore and it makes sense to optimize CPU in such case and lower CPU limit. I think Kubernetes doesn't provide a support for such scenario as of today, I am wondering if there is any workaround to address this issue, the CPU manager relies on CFS, technically wouldn't be possible to modify system configuration (cpu.cfs_quota_us for instance), dynamically after pod creation by Kubernetes using initial CPU limits?

Answer 1

You can use VerticalPodAutoscaler to achieve this. You'll need to define a CustomResource for this that details which pods to target and the policy to use: example:

apiVersion: autoscaling.k8s.io/v1
kind: VerticalPodAutoscaler
metadata:
  name: my-app-vpa
spec:
  targetRef:
    apiVersion: "apps/v1"
    kind:       Deployment
    name:       my-app
  updatePolicy:
    updateMode: "Auto"

More details on installing and using VPA: https://github.com/kubernetes/autoscaler/tree/master/vertical-pod-autoscaler