feat: add ContainerResource type for HPA cpu/memory scaler

[surki]

Context: https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/#container-resource-metrics

Added feature to target to a specific container in cpu/memory scalers

Checklist

• Commits are signed with Developer Certificate of Origin (DCO - learn more)
• Tests have been added
• A PR is opened to update our Helm chart (repo) (if applicable, ie. when deployment manifests are modified)
• A PR is opened to update the documentation on feat: add ContainerResource type for HPA cpu/memory scaler keda-docs#876
• Changelog has been updated and is aligned with our changelog requirements

Fixes #1378

[zroubalik]

What happens if we apply this resource on k8s < 1.20?

[zroubalik]

/run-e2e cpu*
Update: You can check the progress here

[zroubalik]

/run-e2e memory*
Update: You can check the progress here

[surki]

What happens if we apply this resource on k8s < 1.20?

When we run it in k8s < 1.20 or with 1.20+ with the HPAContainerMetrics feature disabled, HPA object creation will fail, which I suppose the KEDA will propagate back to the user.

[zroubalik]

/run-e2e cpu*
Update: You can check the progress here

[tomkerkhove]

What happens if we apply this resource on k8s < 1.20?

When we run it in k8s < 1.20 or with 1.20+ with the HPAContainerMetrics feature disabled, HPA object creation will fail, which I suppose the KEDA will propagate back to the user.

I would, however, improve this so that there is no HPA failure and we log an error + block ScaledObject/ScaledJob creation/edit to fail fast and notify the user.

[zroubalik]

What happens if we apply this resource on k8s < 1.20?

When we run it in k8s < 1.20 or with 1.20+ with the HPAContainerMetrics feature disabled, HPA object creation will fail, which I suppose the KEDA will propagate back to the user.

I would, however, improve this so that there is no HPA failure and we log an error + block ScaledObject/ScaledJob creation/edit to fail fast and notify the user.

That happens already, failure in HPA -> failure in ScaledObject/Job.

[aaron-sysdig]

hey @zroubalik was this change ever released? I dont see it in main? https://github.com/surki/keda/commits/main/pkg/scalers/cpu_memory_scaler.go

[zroubalik]

Yes, it was. You need to check https://github.com/kedacore/keda/ not a fork