gke-rightsizing-checks

GKE Rightsizing Checks

Use this skill before you propose a lower request or limit, a machine type or a node count, and before you claim capacity freed. Raising a limit to stop an OOMKill is a fix, not a rightsizing proposal, and this skill does not apply to it. A request is rarely just a number: an HPA scales on it, a limit may be tied to it, a budget or a claim may share its pods, and the file that declares it may render other clusters too. A proposal that skips those reads looks right and changes something nobody asked to change.

The skill is read-only. It produces checks and arithmetic, and a proposal the person applies through the Platform Agent.

The rule

Run all five checks for each workload or pool you propose to change, and show each one in the answer: what you checked, the command, and what it returned. A check you could not run is reported as not run, with the reason, and you propose no number for the dimension it governs. Every effect claim (nodes freed, CPU or memory freed, a percentage, "fits without scale-up") carries its calculation, with the inputs it used. Give no prices: this deployment has no price data, and a dollar figure here is a guess.

Set the context once:

gcloud container clusters get-credentials <cluster_name> --region <cluster_location>

1. HPA or KEDA on the target

kubectl get hpa -n <namespace> -o jsonpath='{range .items[*]}{.metadata.name} {.spec.scaleTargetRef.kind}/{.spec.scaleTargetRef.name} min={.spec.minReplicas} max={.spec.maxReplicas} {.spec.metrics}{"\n"}{end}'
kubectl get scaledobjects.keda.sh -n <namespace> 2>&1 | head -5

A KEDA error that the resource type does not exist means KEDA is not installed; say so. If an HPA targets the workload on CPU or memory utilization, that utilization is usage divided by the request. A lower request raises the reading, and the HPA adds replicas. Show it with the HPA's own numbers: desired = ceil(current_replicas × (usage / new_request) / target). For example, 4 replicas using 300m each against a 70% target: at a 500m request, ceil(4 × 0.60 / 0.70) = 4; at 350m, ceil(4 × 0.86 / 0.70) = 5. More replicas reserve more in total, so the cut can free nothing. Where the pods also cannot be placed (Pending replicas, a capped pool), the cut makes the backlog larger. The lever is usually the HPA target or minReplicas, not the request.