Python App Deployment Guide

This guide will help you set up and run a Python app locally, and explain how continuous delivery for staging or production is achieved with the help of ArgoCD.

Prerequisites

Before you start, make sure the following tools are installed on your MacOS:

• Docker Desktop with Kubernetes: Download and install from Docker Official Website.
• Kind: Install using Homebrew with brew install kind.
• Kustomize: Install using Homebrew with brew install kustomize.

Local Development

Follow these steps to run the app locally:

1. Create a new cluster using kind with kind create cluster --name local-app.
2. Switch to the newly created cluster with kubectl config use-context kind-local-app.
3. Create a new namespace for the app using kubectl create namespace python-app-develop.
4. Clone the Kustomize repository using git clone https://github.com/Agotfrid/kustomize-example.
5. Navigate to the base of kustomize-example and apply the manifests to the new namespace using kubectl apply -k overlays/develop -n python-app-develop. This command will set up all the required Kubernetes resources including the app, a small MySQL server, required services, secret, ConfigMap, and PVC and PV for database usage.
6. Forward the port of the app service using kubectl port-forward -n python-app-develop svc/python-app-service 5000:80 so that you can use the API on localhost:5000.
7. The API should now be usable!

Continuous Delivery

This section explains how continuous delivery is set up for this project:

1. Once a GitHub Actions task successfully completes the build, tag, and push the Docker image to agotfrid/python-app (or any other artifact registry etc.), the next task updates the kustomization.yaml file in the overlays directory of the Kustomize repo with the new image version for the Python app. The tag used can be either latest or the commit hash of that particular release.
2. In a staging or production environment, we would have ArgoCD installed in the argocd namespace. This namespace includes an argo project and application that monitors the Kustomize repository for any changes. Onc a change is detected (such as an updated image tag), ArgoCD syncs these changes with the cluster, deploying the updated application.