CODEWITHSUNDEEP
kubernetescluster-computingautoscalinghorizontal-pod-autoscalinghorizontalpodautoscaler
Jatin Goyal I
Jatin Goyal I

Reputation: 11

Does Cluster Autoscaler Work Independently of Horizontal Pod Autoscaler (HPA) in Kubernetes?

I'm working on optimizing the scalability of my Kubernetes cluster, and I'm confused about the interaction between Cluster Autoscaler (CA) and Horizontal Pod Autoscaler (HPA).I want to know if Cluster Autoscaler will function independently of HPA, or if they are interdependent.

Scenario: Let's say I have Cluster Autoscaler enabled in my Kubernetes cluster, but Horizontal Pod Autoscaler is disabled. In this setup, if there's a sudden increase in traffic to my services, will Cluster Autoscaler automatically create more pods(and then consequently more nodes) to handle the increased load, or does it require HPA to create more pods?

Background: I understand that Horizontal Pod Autoscaler scales the number of pods based on observed CPU utilization or other metrics. However, I'm not clear on whether Cluster Autoscaler operates independently of HPA or if it relies on HPA for scaling decisions.

Clarifications:

Does Cluster Autoscaler have the capability to scale the number of pods in the absence of Horizontal Pod Autoscaler? If HPA is disabled, will Cluster Autoscaler still monitor the cluster's resource usage and adjust the number of nodes accordingly? Are there any best practices or recommended configurations for using Cluster Autoscaler without Horizontal Pod Autoscaler, or vice versa?

PS: I am working on Azure K8's.

Upvotes: 0

Views: 74

Answers (1)

Daly
Daly

Reputation: 879

The Cluster Autoscaler (CA) and Horizontal Pod Autoscaler (HPA) are not directly dependent on each other. They both looks directly at pod resource metrics to make their scaling decisions.

If there is an HPA but no CA, and a traffic spike comes in, then more pods will be spun up until they use all the resources of the cluster. However the cluster itself will not expand by adding more nodes.

If there is CA but no HPA, and a traffic spike comes in, then the pods will reach their maximum resource constrains. Assuming the pod resource limits are below the node resource limits (which is very typical) then the cluster will not grow. This is because there are still unused resources in the node.

Upvotes: 0

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