911 platform engineers report that HorizontalPodAutoscalers never scale and kubectl top nodes/pods returns errors. Which missing component most directly explains both symptoms?
Select an answer to reveal the explanation.
Short Explanation
HPA and kubectl top both shop at the same metrics counter. If metrics-server is missing, the store is closed—no scaling decisions and no top output.
Full Explanation
metrics-server aggregates resource usage and exposes the metrics.k8s.io API used by kubectl top and by resource-based HorizontalPodAutoscalers. Without it, top commands fail and HPAs lack the CPU/memory signals needed to scale. kube-proxy, StorageClass, and Ingress controllers are not the usual providers of that metrics API.