marcusbb / kopf-flask-operator

Kubernetes Operator for a 2 tier app

This sample project is to show some conceptual example of how you may build an operator for your application - in this case a python Flask application.

Dependencies

Kopf

kopf python based operator framework. This gives us the base of how we can build hooks into Kubernetes.

This is mainly demonstrative of how you can install something using an operator, but can be extended to many other uses cases of maintaining continuity past day 0.

Helm

Why Helm? https://helm.sh/

• It's ubiquitous
• It works
• You are short on time converting or building a deployment mechanism for your favourite DB (or any other software packaged with Helm)

In this case the operator is wrapping Helm to use it as a convenitent installation mechanism for a Postgres.

Pre-requisites

Helm - this is really part of the demonstration to show that you can wrap Helm into your operator

MacOs

brew install helm

Or on your preferred system of choice https://helm.sh/docs/intro/install/

Install Dependencies

pip install -r requirements.txt

[Optional] Install Minikube - this is optional but for testing is quick and painless. https://minikube.sigs.k8s.io/docs/start/

I tested everything locally using minikube on Docker. Feel free to try this out on a full k8s setup! Helm and the kubernetes client will automatically pick up your KUBE_CONFIG.

Install CRD

This is the bit that describes the customized app that you are creating.

kubectl apply -f crd.yaml

Install your application

The code requires a namespace to be present

kubectl create namespace kopf-helm-2-tier
# And use it by default
kubectl config set-context --current --namespace kopf-helm-2-tier

kubectl apply -f my-app.yaml

Operating

All relevant code is in flask-postgres-operator.py This is a realitively naive demonstration, for the most part just demonstrating the mechanics of the operator.

Run the operator using kopf command line. There is some great documentation on

kopf run flask-postgres-operator.py [--verbose]

This should install postgres and the flask deployment on the namespace kopf-helm-2-tier.