Setting up the Vertical Pod Autoscaler

Kubernetes vpa Pod cluster autoscaler Karpenter

3 min read | by Jordi Prats

To be able take advantage of using a Cluster Autoscaler (same applies to AWS Karpenter) we need make sure we properly set the resources any scheduled Pod is requesting to Kubernetes:

  • If we are requesting too much resources, we will be wasting resources
  • If we are requesting too few, the application might end up on a node where it needs to constantly share resources with other Pods

When we are not use the resources a given Pod or container is going to use, we can use the Vertical Pod Autoscaler to help us define them

The Vertical Pod Autoscaler can be found as part of the kubernetes autoscaler git repository. We can choose to install it using the script it provides of use one of the available helm charts, for example cowboysysop's helm. We can install it like so:

$ helm repo add cowboysysop https://cowboysysop.github.io/charts/ $ helm install my-release cowboysysop/vertical-pod-autoscaler

Once installed, we will be able to create a VerticalPodAutoscaler object that will define which mode the VPA operates in:

  • The Auto and Recreate modes automatically apply the CPU and memory recommendations throughout the pod lifetime, deleting any pods that are out of alignment with its recommendations.
  • The Initial mode, applies VPA recommendations only at pod creation.
  • The Off mode only analyzes the Pods to calculate it's recommendations, but we will have to manually update it's definitions

A VerticalPodAutoscaler object that is configured to Off would look like this:

apiVersion: autoscaling.k8s.io/v1 kind: VerticalPodAutoscaler metadata:  name: pet2cattle-webserver spec:  targetRef:  apiVersion: "apps/v1"  kind: Deployment  name: pet2cattle-webserver  updatePolicy:  updateMode: "Off"

Once it's been applied to the system and have been able to collect metrics to make it's recommendations, we can retrieve them using kubectl describe vpa:

$ kubectl get vpa NAME MODE CPU MEM PROVIDED AGE pet2cattle-webserver Off 11m 26214400 True 107s $ kubectl describe vpa pet2cattle-webserver Name: pet2cattle-webserver Namespace: pet2cattle Labels: <none> Annotations: <none> API Version: autoscaling.k8s.io/v1 Kind: VerticalPodAutoscaler Metadata:  (...) Spec:  Target Ref:  API Version: apps/v1  Kind: Deployment  Name: pet2cattle-webserver  Update Policy:  Update Mode: Off Status:  Conditions:  Last Transition Time: 2022-02-07T11:23:51Z  Status: True  Type: RecommendationProvided  Recommendation:  Container Recommendations:  Container Name: webapp  Lower Bound:  Cpu: 10m  Memory: 26214400  Target:  Cpu: 11m  Memory: 26214400  Uncapped Target:  Cpu: 11m  Memory: 26214400  Upper Bound:  Cpu: 541m  Memory: 1160861333  Container Name: socat  Lower Bound:  Cpu: 10m  Memory: 26214400  Target:  Cpu: 11m  Memory: 26214400  Uncapped Target:  Cpu: 11m  Memory: 26214400  Upper Bound:  Cpu: 541m  Memory: 566273869  Container Name: git-sync  Lower Bound:  Cpu: 10m  Memory: 26214400  Target:  Cpu: 11m  Memory: 26214400  Uncapped Target:  Cpu: 11m  Memory: 26214400  Upper Bound:  Cpu: 541m  Memory: 566273869  Container Name: static  Lower Bound:  Cpu: 203m  Memory: 1967849540  Target:  Cpu: 671m  Memory: 2162292018  Uncapped Target:  Cpu: 671m  Memory: 2162292018  Upper Bound:  Cpu: 37571m  Memory: 106473866755 Events: <none>

If we are using the Auto mode but want to skip some of the containers, we can add a containerPolicies to skip it as follows: Exempting containers from applying VPA recommendations

apiVersion: autoscaling.k8s.io/v1 kind: VerticalPodAutoscaler metadata:  name: pet2cattle-webserver spec:  targetRef:  apiVersion: "apps/v1"  kind: Deployment  name: pet2cattle-webserver  updatePolicy:  updateMode: "Auto"   resourcePolicy:   containerPolicies:  - containerName: my-opt-sidecar  mode: "Off"

Posted on 14/02/2022

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