Creating the objects

Previously (Starting the operator), we have created a skeleton operator and learned to start it and see the logs. Now, let’s add a few meaningful reactions to solve our problem (Sample Problem).

We want to create a real PersistentVolumeClaim object immediately when an EphemeralVolumeClaim is created this way:

evc.yaml

apiVersion: kopf.dev/v1
kind: EphemeralVolumeClaim
metadata:
  name: my-claim
spec:
  size: 1G

kubectl apply -f evc.yaml

First, let’s define a template of the persistent volume claim (with the Python template string, so that no extra template engines are needed):

pvc.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: "{name}"
  annotations:
    volume.beta.kubernetes.io/storage-class: standard
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: "{size}"

Let’s extend our only handler. We will use the official Kubernetes client library (pip install kubernetes):

ephemeral.py

import os
import kopf
import kubernetes
import yaml

@kopf.on.create('ephemeralvolumeclaims')
def create_fn(spec, name, namespace, logger, **kwargs):

    size = spec.get('size')
    if not size:
        raise kopf.PermanentError(f"Size must be set. Got {size!r}.")

    path = os.path.join(os.path.dirname(__file__), 'pvc.yaml')
    tmpl = open(path, 'rt').read()
    text = tmpl.format(name=name, size=size)
    data = yaml.safe_load(text)

    api = kubernetes.client.CoreV1Api()
    obj = api.create_namespaced_persistent_volume_claim(
        namespace=namespace,
        body=data,
    )

    logger.info(f"PVC child is created: {obj}")

And let us try it in action (assuming the operator is running in the background):

kubectl apply -f evc.yaml

Wait 1-2 seconds, and take a look:

kubectl get pvc

Now, the PVC can be attached to the pods by the same name, as EVC is named.

Note

If you have to re-run the operator and hit an HTTP 409 error saying “persistentvolumeclaims “my-claim” already exists”, then remove it manually:

kubectl delete pvc my-claim