Skafos

Framework for Kubernetes/Openshift Operators in Python

About

The initial open-source release of this project is provided as-is. That implies that the codebase is only a slightly modified version of what we at ING are using. In the future we would like to extend this Open Source repository with the appropriate pipelines and contribution mechanics. This does imply that your journey for using this project for your own purposes can use some improvement, and we will work on that.

This project is part of the ING Neoria. Neoria contains parts of the ING Container Hosting Platform (ICHP) stack which is used to deliver Namespace-as-a-Service on top of OpenShift.

Quickstart

pip install git+https://github.com/ing-bank/skafos

Create an EventListener, e.g.:

from skafos.event_listener import EventListener


class MyCustomResource(EventListener):
    def create(self):
        print('MyCustomResource was created')

    def update(self):
        print('MyCustomResource was updated')

class Metrics(EventListener):
    pass # TODO: implement metrics here

Register your EventListener, and listen for events:

from skafos.stream_watch import StreamWatch
from kubernetes import config

config.load_incluster_config()
listeners = [Metrics(), MyCustomResource] # Metrics object will be re-used, MyCustomResource will be instantiated on every event
StreamWatch('./crd.yaml', listeners).run() # Blocks forever

In this example we listen to events for a CRD defined in crd.yaml. Note that on startup all existing objects will be passed as Created events (default Kubernetes watch behavior).

For a more detailed example implementation: see the basic example More details on how this framework works can be found in the docs folder

My First Operator

1. Create a basic crd description ( https://kubernetes.io/docs/tasks/access-kubernetes-api/custom-resources/custom-resource-definitions/#create-a-customresourcedefinition ) NOTE: if you are not on kubernetes 1.16 or higher: use "apiextensions.k8s.io/v1beta1"
2. Create your resources implementation with inheriting the EventLister class, with at least the create method Example
3. Create your app.py
4. Start it python3 app.py

Note, in Kubernetes watches when an event stream starts all the existing objects will be passed as Created events.

Running without CRD

It is possible to create an Operator without CRD. In this case you are not listening to custom objects, but the Core API. You can specify what object you want to watch by using a dict:

crd = {
    'args': [],
    'kwargs': {},
    'method': lambda x: x.list_namespace
}

OPERATOR = StreamWatch(crd, [MyCustomListener])
OPERATOR.run()  # Blocking call

Using args and kwargs you can add parameters to the Core API method that you want to watch. In this case the list_namespace method is watched, and it has no parameters.