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Bootiful Kubernetes

Operators

Tiffany Jernigan �Senior Developer Advocate, www.tiffanyfay.dev�

Ties van de Ven �Software Quality Expert @Alliander www.tiesvandeven.nl

sli.do #geecon

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Bootiful Kubernetes Operators

Tiffany Jernigan �Senior Developer Advocate, www.tiffanyfay.dev�

Ties van de Ven �Software Quality Expert @Alliander

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Who We Are

�

Tiffany Jernigan

Senior Developer Advocate�Open to Hire

www.tiffanyfay.dev

X (Twitter): @tiffany f ayj�linkedin.com/in/tiffanyfayj

�

Ties van de Ven

Software Quality Expert �Alliander

www.tiesvandeven.nl �X (Twitter): @ties_ven�linkedin.com/in/tiesvandeven

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Agenda

What is an Operator?
How does Kubernetes work?
Custom operators
Building our own operator

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The Operator pattern

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[Ties]

There was a time that when you finally after weeks of coding had a finished product, and then actually had to call another team to deploy the application for you because you were not allowed to do that?

Well this is what an operator like our raccoon friend here was supposed to do. (as a side note, Tiffany asked me to do this slide because she can get a bit weird when cute raccoon are involved).

But an Operator is there to pick up the phone, hear what you want done and will then manually do this task for you. In our case, deploy the application

These days we no longer have a raccoon army do do this, and we automated the process using kubernetes

============

* [Operator Pattern](https://kubernetes.io/docs/concepts/extend-kubernetes/operator/)

* Kubernetes implements the Operator pattern using Controllers and Custom Resource Definitions (CRD)

* An example of this is the Configmap Controller which creates a Configmap based on your specifications in YAML

* A Config map is a ...

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High level overview

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Control Loop

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Controller

�SS

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Desired state

+

-

Input

Measured �error

Measured �temperature

Current state

�S��

S

24�

Output

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[Tiffany]

A good analogy of this is the thermostat you have at home. You communicate the desired temperature by turning or pressing some buttons and then it will continuously check if the current temperature matches the desired temperature.

If not it will instruct the heater to turn on, until the room has the desired temperature on which the heater can be turned off.

It then keeps on monitoring in case the room temperature drops again so it can turn the heater on again in case this is needed.

This is called a control loop, and this is how Controllers make sure everything works.

===============

In robotics and automation, a control loop is a non-terminating loop (i.e., a loop that runs forever) that regulates the state of a system and tries to match the current state of the system with a desired state.

For example, when we set the temperature of a thermostat, that's the desired state. The actual room temperature is the current state. The thermostat acts to bring the current state closer to the desired state by turning equipment (heaters, AC, heat pumps...) on or off.

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Built-in Kubernetes Controllers

Deployment
ReplicaSet
DaemonSet
StatefulSet
Job
CronJob

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Kubernetes speak

apiVersion: batch/v1

kind: CronJob

metadata:

name: hello

spec:

schedule: "* * * * *"

…

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Kubernetes Controller Pattern

apiVersion: batch/v1

kind: CronJob

metadata:

name: hello

spec:

schedule: "* * * * *"

Control Plane

API Server

etcd (DB)

scheduler

controller manager

CronJobController

Requeue after error

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Operator chaining

CronJobController

JobController

PodController

Kubernetes API

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Custom Operators

https://spring.io/blog/2021/11/19/get-to-know-a-kubernetes-operator

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Why write your own operator?

I want some functionality

Can I do this in Kubernetes?

Write your own operator

Do not write your own operator

Is there an off the shelf operator?

yes

no

yes

no

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Why write your own operator?

Automating (complex) tasks for teams
Credential management

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[Ties]

### Do complex tasks for teams

Everything operators do can also be done in pipelines, so why use an operator

For example if you want every team in your organisation to set up a specific authentication flow which contains multiple steps it can be beneficial to create an operator to do this for you. This way the team only has to supply the absolute minimum amount of information to have everything configured for them.

### Prevent teams from having privileges

Another reason you want to move creation of certain resources to a controller is if those resources need to have high level privileges. If your authentication flow for example needs to make an adjustment in Active Directory, you do not necessarily want to give all the teams in your organisation privileges to do that. By using an Operator the team can only communicate to the operator using yaml and the Operator can handle everything else. It’s basically a rest api with yaml instead of json

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Pitfalls

Out of sync
Ownership

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Building an Operator

Examples of Operator frameworks/libraries

Or just use a REST client��https://kubernetes.io/docs/reference/using-api/client-libraries/

Officially supported:

C
dotnet
Go
Haskell
Java
JavaScript
Perl
Python
Ruby

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Building our own operator

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What will we need

Custom Resource Definition (CRD)
Controller

Reconciler

Role bindings
Deployment

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@ties_ven�www.tiesvandeven.nl�linkedin.com/in/tiesvandeven �

@tiffanyfayj

www.tiffanyfay.dev�linkedin.com/in/tiffanyfayj

https://via.vmw.com/bootiful-k8s-operators

Thank You