TIL Using Kompose to generate Kubernetes manifests for Python Flask apps

  • Input: A Flask app that is not Kubernetes-aware
    • Output: Kubernetes manifests for deploying that Flask app

This sounds like a place where kompose can shine. ☀️

🧵 Prerequisites

I am going to deploy httpmeow, the Flask app I built for the HTTP Response Status Cats that I wrote about in November. That project is publicly available if you'd like to follow along. First things first: httpmeow is not presently packaged for use with Docker or Kubernetes. (It doesn't need to be: it's deployed to Google Cloud Run and could probably be a static site.)

It's simple enough that something like this will work:

# docker-compose.yaml
version: '3'

    build: '.'
    image: registry.gitlab.com/brie/httpmeow:v0
      - '5000:8008'

🚀 Let's go!

There are a host of installation options for kompose. Let's use Docker; we'll need to deviate a bit from what is currently in the docs. This is what worked well for me:

git clone https://github.com/kubernetes/kompose.git
cd kompose
docker build -t kompose:v0 .
docker run --rm -it -v $PWD:/opt kompose:v0  sh -c "cd /opt && kompose convert"

Once it's ready, go back to the directory where the Flask app is stored and run:

docker run --rm -it -v $PWD:/opt kompose:v0  sh -c "cd /opt && kompose convert"

The output is promising:

INFO Network opt-default is detected at Source, shall be converted to equivalent NetworkPolicy at Destination
INFO Kubernetes file "httpmeow-service.yaml" created
INFO Kubernetes file "httpmeow-deployment.yaml" created
INFO Kubernetes file "opt-default-networkpolicy.yaml" created

🌈 ...and beyond!

From here, you can add annotations and other adjustments to the manifests. When they are all ready to go, they can be deployed with kubectl apply:

kubectl apply -f httpmeow-service.yaml,httpmeow-deployment.yaml

Depending on where you are deploying, you might want to skip the network policy.

If all is well, things will be created and you can do kubectl get deployments and kubectl logs deployment/httpmeow.

ℹ️ About this TIL snippet: Created 2023-02-22T01:57:11-05:00 · View the source