kubectl-operator VS operator-sdk

Kubernetes Operators simplify the management of complex applications on Kubernetes. In this guide, we'll walk through creating a simple Kubernetes Operator using the Operator Framework. We'll also cover setting up a local Kubernetes cluster with KIND (Kubernetes in Docker) and deploying the Operator to the KIND cluster.

There's a kubectl extension for it too. https://github.com/operator-framework/kubectl-operator

Since Go got generics, working with the Kubernetes API could become far more ergonomic. It's been pulling teeth until now. I'm eager to see how the upstream APIs change over time.

In the mean time, one of the creators of the Operator Framework[0] built a bunch of useful patterns using generics that we used to build the SpiceDB Operator[1] called controller-idioms[2].

Does anyone know of other efforts to improve the status quo?

[0]: https://operatorframework.io

[1]: https://github.com/authzed/spicedb-operator

[2]: https://github.com/authzed/controller-idioms

There are many frameworks, like the Operator Framework (https://operatorframework.io/) to the MetaController (https://github.com/metacontroller/metacontroller) to KubeBuilder(https://github.com/kubernetes-sigs/kubebuilder) to the Kubernetes Operator Framework (kopf, https://kopf.readthedocs.io/en/stable/), among others.

Operator lifecycle manager (OLM) is a Kubernetes feature & is part of Operator framework which provides tools that helps in the development and management of operators. OpenShift 4.x is build using different operators that manages cluster components like api-server, etcd, authentication, OAuth, ingress, etc. OpenShift makes use of OLM to install these operators as part of cluster build & OLM comes by default with OpenShift. OLM is an operator itself and understanding how it manages the operator lifecycle using different CRD’s & its flow is important, which I have explained in my article.

The documentation gives you all available options, but many of them are optional. If you know the package name of the operator (which you can get either via oc get packagemanifests or kubectl operator list-available from the kubectl plugin all you really need is:

client-go is the official Golang client for Kubernetes, responsible for interacting with the Kubernetes API server using REST API. In fact, client-go can do almost anything, not just for writing operators. Even the internal implementation of kubectl is based on client-go. As for more specialized frameworks used to write operators, including controller-runtime, kubebuilder, and operator-sdk, they will be introduced later in this series.

Operator SDK

operator-sdk: brew install operator-sdk

The operator that I've been working on is designed to manage the full lifecycle of a QuestDB database instance, including version and hardware upgrades, config changes, backups, and (eventually) recovery from node failure. I used the Operator SDK and kubebuilder frameworks to provide scaffolding and API support.

I've recently been working on an operator (built using the operator-sdk) that manages cluster node lifecycles. Kind allows you to spin up clusters with multiple nodes, using a Docker container per-node and joining them using a common Docker network. However, the kind executable does not allow you to modify an existing cluster by adding or removing a node.

To illustrate what we can do with an operator, I will create a proof of concept using operator-sdk. According to the official website::

Besides the frameworks TFA lists, you can also build Operators in Ansible or Helm.

https://sdk.operatorframework.io/

Operator SDK is basically just a thin wrapper for kube-builder