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Monitor controller-runtime without melting the Kubernetes API server

A practical workflow to catch LIST storms, stale caches, reconcile queues, and control-plane alerts before your operator becomes the incident. A generous little gift from automation.

Learn how to monitor Kubernetes controllers built with controller-runtime using Prometheus, workqueue metrics, API server signals, promtool rules, and canary validation.

Created: August 27, 2026

Published: August 27, 2026

Estimated time45 min

LevelAdvanced

Before you startPrometheus scraping the API server and custom controllers

PlatformsLinux / Docker

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Linux

Diagnose from a Linux workstation with kubectl, curl against Prometheus, and promtool.

kubectlcurlpromtool

Check controller state

kubectl get pods -n platform -l app=checkout-operator -o wide

Inspect recent errors

kubectl logs deploy/checkout-operator -n platform --tail=120 | egrep -i 'reconcile|watch|cache|timeout|throttle|error'

Query reconcile queues

curl -G 'http://localhost:9090/api/v1/query' --data-urlencode 'query=max by (controller)(workqueue_depth{job="checkout-operator"})'

Test rules

promtool test rules tests/controller-runtime-cache-pressure.test.yaml

Also available inMonitorizar controller-runtime sin fundir el API server de Kubernetes

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