Starting the operator

Previously, we have defined a problem that we are solving, and created the custom resource definitions for the ephemeral volume claims.

Now, we are ready to write some logic for this kind of object. Let us start with an operator skeleton that does nothing useful — just to see how it can be started.

ephemeral.py

import kopf
import logging
from typing import Any

@kopf.on.create('ephemeralvolumeclaims')
def create_fn(body: kopf.Body, **_: Any) -> None:
    logging.info(f"A handler is called with body: {body}")

Note

Despite an obvious desire, do not name the file operator.py, since there is a built-in module in Python 3 with this name, and there could be potential conflicts on the imports.

Let us run the operator and see what happens:

kopf run ephemeral.py --verbose

The output looks like this:

[2019-05-31 10:42:11,870] kopf.config          [DEBUG   ] configured via kubeconfig file
[2019-05-31 10:42:11,913] kopf.reactor.peering [WARNING ] Default peering object is not found, falling back to the standalone mode.
[2019-05-31 10:42:12,037] kopf.reactor.handlin [DEBUG   ] [default/my-claim] First appearance: {'apiVersion': 'kopf.dev/v1', 'kind': 'EphemeralVolumeClaim', 'metadata': {'annotations': {'kubectl.kubernetes.io/last-applied-configuration': '{"apiVersion":"kopf.dev/v1","kind":"EphemeralVolumeClaim","metadata":{"annotations":{},"name":"my-claim","namespace":"default"}}\n'}, 'creationTimestamp': '2019-05-29T00:41:57Z', 'generation': 1, 'name': 'my-claim', 'namespace': 'default', 'resourceVersion': '47720', 'selfLink': '/apis/kopf.dev/v1/namespaces/default/ephemeralvolumeclaims/my-claim', 'uid': '904c2b9b-81aa-11e9-a202-a6e6b278a294'}}
[2019-05-31 10:42:12,038] kopf.reactor.handlin [DEBUG   ] [default/my-claim] Adding the finalizer, thus preventing the actual deletion.
[2019-05-31 10:42:12,038] kopf.reactor.handlin [DEBUG   ] [default/my-claim] Patching with: {'metadata': {'finalizers': ['KopfFinalizerMarker']}}
[2019-05-31 10:42:12,165] kopf.reactor.handlin [DEBUG   ] [default/my-claim] Creation is in progress: {'apiVersion': 'kopf.dev/v1', 'kind': 'EphemeralVolumeClaim', 'metadata': {'annotations': {'kubectl.kubernetes.io/last-applied-configuration': '{"apiVersion":"kopf.dev/v1","kind":"EphemeralVolumeClaim","metadata":{"annotations":{},"name":"my-claim","namespace":"default"}}\n'}, 'creationTimestamp': '2019-05-29T00:41:57Z', 'finalizers': ['KopfFinalizerMarker'], 'generation': 1, 'name': 'my-claim', 'namespace': 'default', 'resourceVersion': '47732', 'selfLink': '/apis/kopf.dev/v1/namespaces/default/ephemeralvolumeclaims/my-claim', 'uid': '904c2b9b-81aa-11e9-a202-a6e6b278a294'}}
[2019-05-31 10:42:12,166] root                 [INFO    ] A handler is called with body: {'apiVersion': 'kopf.dev/v1', 'kind': 'EphemeralVolumeClaim', 'metadata': {'annotations': {'kubectl.kubernetes.io/last-applied-configuration': '{"apiVersion":"kopf.dev/v1","kind":"EphemeralVolumeClaim","metadata":{"annotations":{},"name":"my-claim","namespace":"default"}}\n'}, 'creationTimestamp': '2019-05-29T00:41:57Z', 'finalizers': ['KopfFinalizerMarker'], 'generation': 1, 'name': 'my-claim', 'namespace': 'default', 'resourceVersion': '47732', 'selfLink': '/apis/kopf.dev/v1/namespaces/default/ephemeralvolumeclaims/my-claim', 'uid': '904c2b9b-81aa-11e9-a202-a6e6b278a294'}, 'spec': {}, 'status': {}}
[2019-05-31 10:42:12,168] kopf.reactor.handlin [DEBUG   ] [default/my-claim] Invoking handler 'create_fn'.
[2019-05-31 10:42:12,173] kopf.reactor.handlin [INFO    ] [default/my-claim] Handler 'create_fn' succeeded.
[2019-05-31 10:42:12,210] kopf.reactor.handlin [INFO    ] [default/my-claim] All handlers succeeded for creation.
[2019-05-31 10:42:12,223] kopf.reactor.handlin [DEBUG   ] [default/my-claim] Patching with: {'status': {'kopf': {'progress': None}}, 'metadata': {'annotations': {'kopf.zalando.org/last-handled-configuration': '{"apiVersion": "kopf.dev/v1", "kind": "EphemeralVolumeClaim", "metadata": {"name": "my-claim", "namespace": "default"}, "spec": {}}'}}}
[2019-05-31 10:42:12,342] kopf.reactor.handlin [DEBUG   ] [default/my-claim] Updating is in progress: {'apiVersion': 'kopf.dev/v1', 'kind': 'EphemeralVolumeClaim', 'metadata': {'annotations': {'kopf.zalando.org/last-handled-configuration': '{"apiVersion": "kopf.dev/v1", "kind": "EphemeralVolumeClaim", "metadata": {"name": "my-claim", "namespace": "default"}, "spec": {}}', 'kubectl.kubernetes.io/last-applied-configuration': '{"apiVersion":"kopf.dev/v1","kind":"EphemeralVolumeClaim","metadata":{"annotations":{},"name":"my-claim","namespace":"default"}}\n'}, 'creationTimestamp': '2019-05-29T00:41:57Z', 'finalizers': ['KopfFinalizerMarker'], 'generation': 2, 'name': 'my-claim', 'namespace': 'default', 'resourceVersion': '47735', 'selfLink': '/apis/kopf.dev/v1/namespaces/default/ephemeralvolumeclaims/my-claim', 'uid': '904c2b9b-81aa-11e9-a202-a6e6b278a294'}, 'status': {'kopf': {}}}
[2019-05-31 10:42:12,343] kopf.reactor.handlin [INFO    ] [default/my-claim] All handlers succeeded for update.
[2019-05-31 10:42:12,362] kopf.reactor.handlin [DEBUG   ] [default/my-claim] Patching with: {'status': {'kopf': {'progress': None}}, 'metadata': {'annotations': {'kopf.zalando.org/last-handled-configuration': '{"apiVersion": "kopf.dev/v1", "kind": "EphemeralVolumeClaim", "metadata": {"name": "my-claim", "namespace": "default"}, "spec": {}}'}}}

Note that the operator detected an object that was created before the operator itself was started, and handled it because it had not been handled before.

Now, you can stop the operator with Ctrl-C (twice), and start it again:

kopf run ephemeral.py --verbose

The operator will not handle the object again, as it has already been successfully handled. This is important when the operator is restarted — whether running as a deployed pod or restarted manually for debugging.

Let us delete and re-create the same object to see the operator reacting:

kubectl delete -f obj.yaml
kubectl apply -f obj.yaml