# KubeCon NA, 2021
## Title: "Trigger" Warning: An Autopsy of The Kubernetes Core

> - What do you expect the audience to gain from your presentation?
> - Why should YOU be the one to give this talk? You have a unique story. Tell it.
> - Be prepared to explain how this fits into the CNCF and overall Open Source Ecosystem.

## Session description
"Kubernetes is a platform for building platforms", is a well-known statement today, but why is it built the way it is?

Kubernetes is designed to be "Level Triggered" as opposed to an "Edge Triggered", meaning that it cares more about the "state" that it is in rather than the individual "events" that occur. But why?

Other than being level triggered, Kubernetes is a fairly Declarative system with the Controller pattern at its core. We will look at how these design decisions enable K8s to work towards a state of "homeostasis" and how controllers enable this. But, why controllers and how did they come about? Let's dive into the field of control theory, more specifically -- PID control to see what inspired the controller pattern.

This talk will dive deep into the fundamental 'why' of the Kubernetes design saga and help you understand the Kubernetes machine in a deeper sense, bringing together the concepts of Level Triggered Systems, Declarative Systems and Control Theory.

## Benefits to the ecosystem
This talk dives deep into the intuition behind the theoretical underpinnings of the K8s design such as Level Triggering, PID Control, and Declarative Design, explained with the help of demos, in hopes of better understanding K8s and making the journey of becoming comfortable with what's what, a little easier.

I had a difficult time understanding how K8s worked, understanding these topics was the most helpful because by understanding declarative design and control loops, I was able to understand the finer implementation details such as informers, list+watch, finalizers, reflectors and their purpose and is largely the reason I've been able to contribute to sig-apimachinery.

Note: there have been talks in the past related to these topics but none that talk about all of them together. This talk ties together these topics and their relation to K8s. Ex: HPA is a P controller that changes the spec and does not actually touch the pods (level-triggered - care about state and not events).

A (very) naive version of this talk that I gave in my college:
| Type | Link |
| ---------------- | -------- |
| Recording | https://youtu.be/nz99WrdgRuA |
| Demo Source Code | https://github.com/MadhavJivrajani/pesos-imperative-declarative |