Summary - Operator

Combine CRD and reconcile to describe an operator.

Summary: operators

In this group:

Operator = CRD + a controller containing operational knowledge; it manages the app after installation too.
Reconcile is idempotent: read the custom resource, create/conform the child objects, write the status, requeue if needed.
ownerReferences enable garbage collection and triggering; finalizers clean up external resources.
Operator SDK/Kubebuilder: init, create api, make manifests from markers, make install/run/deploy.
The user only interacts with the custom resource; status.conditions and kubectl wait report readiness.

kubectl apply -f yedek.yaml
kubectl wait --for=condition=Ready yedek/magaza-gece -n magaza

Exercise Inspect a stuck object

Write three commands: print the finalizers of the magaza-gece Yedek in magaza with jsonpath='{.metadata.finalizers}'; show the last 20 lines of the operator's logs from deploy/yedek-operator-controller-manager in yedek-operator-system; list the pods in yedek-operator-system.

Show example solution

kubectl get yedek magaza-gece -n magaza -o jsonpath='{.metadata.finalizers}'
kubectl logs -n yedek-operator-system deploy/yedek-operator-controller-manager --tail=20
kubectl get pods -n yedek-operator-system

Test yourself

If a custom resource gets stuck in Terminating while being deleted, what is the likely cause?
- The disk is full
- The name is too long
- A printcolumn is missing in the CRD
- The operator that would remove the finalizer isn't running
Show answer

The operator that would remove the finalizer isn't running — The object isn't deleted until the finalizer list is empty.

Add a marker for cleanup before deletion.

metadata:
  ____: ["ornek.com/s3-temizle"]

Show answer

metadata:
  finalizers: ["ornek.com/s3-temizle"]

Match.

CRD

Data model
denetleyici

Behaviour
ownerReferences

Garbage collection
finalizer

Deletion hook

Next lesson: What is a service mesh?

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