Diegolden

Topic 4: Controllers And Reconciliation

2 min read

Topic 4: Controllers And Reconciliation

Official baseline: (The Kubernetes Authors, 2026b, 2026a, 2026c). My working version: Kubernetes works because controllers keep comparing desired state with observed state. That loop is the product.

Mental Model

Kubernetes works because controllers keep comparing desired state with observed state. That loop is the product.

Notes

  • A controller does not usually perform one big action; it keeps making small corrections.
  • Most higher-level resources are contracts that controllers interpret.
  • Debugging means reading events and asking which controller owns the stalled transition.

Homelab Angle

This model is what makes GitOps natural: Git changes desired state, controllers do the mechanical work.

Verify It

  • Read the object status before changing the manifest.
  • Check events for the controller or node that is actually complaining.
  • Confirm the official source linked below still matches the cluster version you run.

Common Failure Modes

  • Treating the YAML object as the system, instead of one input to a reconciliation loop.
  • Debugging from outside the cluster when the failure only exists inside cluster networking or node state.
  • Forgetting that Kubernetes version, addon version, and runtime behavior are linked.

Sources

  • Kubernetes Components - source path: content/en/docs/concepts/overview/components.md, commit 8cc9e19b8eec8d5cf49eacd66f86a81648edb1a0.
  • Cluster Architecture - source path: content/en/docs/concepts/architecture/_index.md, commit 8cc9e19b8eec8d5cf49eacd66f86a81648edb1a0.
  • The Kubernetes API - source path: content/en/docs/concepts/overview/kubernetes-api.md, commit 8cc9e19b8eec8d5cf49eacd66f86a81648edb1a0.
  • Kubernetes documentation is licensed under CC BY 4.0; these notes are original commentary and link back to the official source.
The Kubernetes Authors. (2026a). Cluster Architecture. https://kubernetes.io/docs/concepts/architecture/
The Kubernetes Authors. (2026b). Kubernetes Components. https://kubernetes.io/docs/concepts/overview/components/
The Kubernetes Authors. (2026c). The Kubernetes API. https://kubernetes.io/docs/concepts/overview/kubernetes-api/

Graph View

Backlinks