[TBD]Role of k8s operator for stateful applications

Introduction

Laymen explanation

The Operator pattern captures how you can write code to automate a task beyond what Kubernetes itself provides.

Technical explanation

Operators are controller which acts on CRDs

The Operator pattern aims to capture the key aim of a human operator who is managing a service or set of services. Human operators who look after specific applications and services have deep knowledge of how the system ought to behave, how to deploy it, and how to react if there are problems.

Why operator needed?

Stateful applications, like databases and monitoring systems, require additional domain-specific knowledge that Kubernetes doesn’t have. It needs this knowledge in order to scale, upgrade, and reconfigure these applications.

Features

Operators are clients of the Kubernetes API that act as controllers for a Custom Resource.
A Kubernetes operator is a method of packaging, deploying, and managing a Kubernetes application.
A Kubernetes application is both deployed on Kubernetes and managed using the Kubernetes API (application programming interface) and kubectl tooling.
The actions a Kubernetes operator performs can include almost anything:
- scaling a complex app,
- application version upgrades, or
- even managing kernel modules for nodes in a computational cluster with specialized hardware.