⚠️ THIS PROJECT IS NO LONGER MAINTAINED ⚠️

This repository has been archived and is no longer actively maintained.

If you have questions or need information about this project, please contact: tim@kartoza.com

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Kubernetes Flask "Hello World" Environment

This directory sets up a simple Kubernetes environment using Minikube with Podman, featuring a Flask server that serves a "Hello World" page. This setup uses Nix and Direnv to automatically activate the environment.

Prerequisites

Ensure you have Nix, Direnv, and Podman installed on your system.

Setting up NixOS for rootless Podman

1. Edit your configuration.nix to include the following settings:

   {
     # Note mutually exclusive with the docker service
     environment.systemPackages = with pkgs; [
       podman
       docker-compose
     ];
   
     virtualisation = {
       podman = {
         enable = true;
         # Create a `docker` alias for podman, to use it as a drop-in replacement
         dockerCompat = true;
         # Required for containers under podman-compose to be able to talk to each other.
         defaultNetwork.settings = {
           dns_enabled = true;
         };
       };
     };
   
     # Other configuration settings...
   
     # Set kernel parameters
     boot.kernelParams = ["unprivileged_userns_clone=1"];
   
     # Set sysctl settings
     boot.kernel.sysctl."kernel.unprivileged_userns_clone" = true;
   
     # Enable Podman socket for rootless mode
     systemd.user.services.podman = {
       description = "Podman API Socket";
       serviceConfig = {
         ExecStart = "${pkgs.podman}/bin/podman system service --time=0";
         Restart = "always";
         ExecStartPost = "-${pkgs.podman}/bin/podman info";
       };
       wantedBy = ["default.target"];
     };
   
     # Add Polkit rule to allow users in the wheel group to manage services
     environment.etc."polkit-1/rules.d/10-wheel-group.rules".text = ''
       polkit.addRule(function(action, subject) {
         if (action.id == "org.freedesktop.systemd1.manage-units" &&
             subject.isInGroup("wheel")) {
           return polkit.Result.YES;
         }
       });
     '';
   }

2. Apply the configuration:

   sudo nixos-rebuild switch

Setup

1. Clone the repository and navigate into the directory:

   git clone <your-repo-url>
   cd <your-repo-directory>

2. Allow Direnv to load the environment:

   direnv allow

3. Enter the directory:

   Simply entering the directory will automatically start the Nix shell, Podman, Minikube, and deploy the Flask Helm chart.

Managing the Cluster with kubectl

Check Pod Status

To check the status of the pods:

kubectl get pods -A

This command lists all the pods running in your cluster, along with their status. It helps you verify if your application pods are running correctly.

Scaling the Deployment

To scale the Flask deployment to 3 replicas:

kubectl scale deployment flask-app --replicas=3

This command scales the number of replicas (instances) of the Flask application. Scaling up increases the application's availability and load capacity.

Adding Nodes to the Minikube Cluster

To add more nodes to the Minikube cluster:

minikube node add

This command adds an additional node to your Minikube cluster, which can help distribute the workload and improve the cluster's resilience and capacity.

Restarting the Flask Service

To restart the Flask service:

kubectl rollout restart deployment flask-app

This command restarts the deployment by rolling out a new version of the pods. It's useful for applying configuration changes or recovering from errors.

Checking Logs

To check the logs of the Flask pod:

kubectl logs <flask-app-pod-name>

Replace <flask-app-pod-name> with the actual name of the Flask pod. This command fetches the logs from a specific pod, which helps in debugging and monitoring the application.

Checking Service Health

To describe the Flask service and check its health:

kubectl describe service flask-app

This command provides detailed information about the Flask service, including its configuration, status, and events. It's useful for diagnosing issues with the service.

Stopping the Minikube Cluster

To stop the Minikube cluster:

minikube stop

This command stops all nodes in the Minikube cluster. It's useful for conserving resources when the cluster is not needed.

Deleting the Flask Deployment

To delete the Flask deployment:

helm uninstall flask-app

This command removes the Flask application deployed via Helm. It cleans up all associated resources like pods, services, and configuration.

Accessing the Flask Application

Using Port Forwarding

Forward a local port to the Flask application's service port:

kubectl port-forward svc/flask-app 8080:80

You should now be able to access the Flask application at http://localhost:8080.

Using Minikube Tunnel

Alternatively, you can use Minikube's tunnel to expose the service:

minikube tunnel

Notes

• Ensure Podman is running on your machine, as Minikube requires a container runtime to function properly.
• The Flask application runs on port 8080 by default. Adjust the configuration if needed.
• Use the kubectl commands provided to manage and monitor your Kubernetes cluster effectively.

Files

• shell.nix: Nix shell configuration to set up the environment.
• .envrc: Direnv configuration to automatically activate the Nix shell.
• values.yaml: Helm values file for the Flask application.
• flask_app/app.py: Simple Flask application.
• flask_app/Dockerfile: Dockerfile to build the Flask application image.

This README.md file provides comprehensive instructions on setting up and managing the Kubernetes cluster with the Flask application, including detailed explanations of each management action.