Building ferctl top: Kubernetes resource usage vs requests and limits
Series: Platform engineering with Go | Topics: Go, Kubernetes, Cobra, client-go, metrics-server, Platform Engineering This is part of the Platform Engineering with Go series. This post builds on the Cobra CLI patterns from post 4 and client-go from post 3. Read post 4 first if you haven't yet. kubectl top tells you what's happening. It doesn't tell you how close to the edge you are. In post 3 and post 4 , we built a health reporter and learned how to structure a Go CLI with Cobra. Now we put both together into something with real operational value. kubectl top pods -n production NAME CPU ( cores ) MEMORY ( bytes ) go-api-7d6b9f8c4-xk2pq 240m 490Mi go-api-7d6b9f8c4-mn9rt 180m 210Mi go-api-7d6b9f8c4-p8wvz 200m 198Mi That first pod is using 490Mi of memory. Is that fine or is that a problem? Without knowing the limit, you can't tell. You'd have to run kubectl describe pod go-api-7d6b9f8c4-xk2pq , find the resources section, do the mental arithmetic, and repeat for every pod you care about. ferctl top does all of that in one command: ferctl top -n production NAMESPACE NAME CPU USE CPU REQ CPU LIM CPU% MEM USE MEM REQ MEM LIM MEM% STATUS production go-api-7d6b9f8c4-xk2pq 240m 250m 500m 48% 490Mi 256Mi 512Mi 95% !! CRITICAL production go-api-7d6b9f8c4-mn9rt 180m 250m 500m 36% 210Mi 256Mi 512Mi 41% OK production go-api-7d6b9f8c4-p8wvz 200m 250m 500m 40% 198Mi 256Mi 512Mi 38% OK One pod is at 95% of its memory limit. In production, that's a page waiting to happen. ferctl top catches it before it becomes an incident. What you'll learn How to extend the Cobra CLI structure from post 4 with a real subcommand How to query the metrics-server API using k8s.io/metrics How to correlate live metrics with pod specs to show usage vs limits How to implement configurable near-limit warnings How to format clean aligned output with tabwriter How to verify the tool against your real minikube cluster Prerequisites Posts 1–4 read; client-go patterns from post 3 , Cobra CLI structure from pos