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Controller-runtime golden signals: catch cache lag before blaming the API server

A practical guide to separate informer lag, saturated queues, REST-client throttling, and real API-server issues in Kubernetes controllers.

Learn how to instrument and diagnose Kubernetes controllers with controller-runtime, workqueue, cache, and REST-client metrics before tuning concurrency or restarting pods blindly.

Created: July 30, 2026

Published: July 30, 2026

Estimated time40 min

LevelAdvanced

Before you startRead kubectl access to the controller namespace

PlatformsLinux

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Linux

kubectl, Prometheus, and ServiceMonitor flow to validate controller-runtime based controllers in Kubernetes.

kubectlcurlPrometheus Operator optional

List recent controller and API events

kubectl get events -n platform-controllers --sort-by=.lastTimestamp | tail -40

Check controller resource pressure

kubectl top pods -n platform-controllers

Inspect recent reconciler errors

kubectl logs deploy/orders-controller -n platform-controllers --tail=120 | egrep 'reconcile|cache|throttle|too old resource version|error'

Read controller metrics locally

kubectl port-forward -n platform-controllers deploy/orders-controller 8080:8080 &
curl -s localhost:8080/metrics | egrep 'workqueue|controller_runtime|rest_client'

Also available inGolden signals para controller-runtime: detectar caché lenta antes de culpar al API server

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