This is a small project to demonstrate a basic understanding of Kubernetes.

Prompt:

• Create a hello world application and deploy it within Kubernetes.
• The application should accept HTTP requests from clients and simply return “Hello, world!”.
• The application should be reachable from a browser/client outside of the cluster.
• The application should keep an audit log of IP addresses which sent a request to the application.
• Be prepared to talk about how your application works, paying particular attention to the path the HTTP request takes from the browser to the application.

Requirements:

• The application can be written by you, or you can use one from the internet.
• The application can be written in any language. Using Golang is a stretch goal.
• The Kubernetes cluster can be any distribution. For simplicity, kind is recommended.
• The audit log should persist through container restarts. Strive to persist the audit log permanently.
• There are no limitations on the technologies used for traffic ingress or storage.
• Accepting HTTPS requests is not a requirement.

Github Project

I created the application in go; see main.go in the app folder. The app exposes two resources:

/hello returns the “Hello, world!” string and logs the ip address.
/logs returns the contents of the log file for test verification purposes.

As suggested I used kind for the distribution and created the kind-config.yml file in the kubernetes folder. I also created the kube-config.yml to define all the kubernetes components (deployment, service, persistent volume, etc.).

With everything created, I then ran through the below steps to test and verify the requirements.

Note, these steps assume docker desktop, go, kubectl, and kind are installed

1. Build main.go.

% go build
% go mod tidy

2. Build the image.

% docker build -t hello-app $KUBE_HOME/app

3. Create the cluster and load the image into the worker. Add the nginx controller and wait for it to be ready.

% kind create cluster --name=hello-cluster --config=$KUBE_HOME/kubernetes/kind-config.yml
% kind load docker-image hello-app --name hello-cluster --nodes hello-cluster-worker
% kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/main/deploy/static/provider/kind/deploy.yaml
% kubectl wait --namespace ingress-nginx \
  --for=condition=ready pod \
  --selector=app.kubernetes.io/component=controller \
  --timeout=90s

4. Apply the kubernetes config file.

% kubectl apply -f $KUBE_HOME/kubernetes/kube-config.yml

5. Verify accessibility and cause a log event.

% curl http://localhost/hello 
  OR 
view at http://localhost/hello

6. Verify the log was created in the logs directory.

% curl http://localhost/logs 
  OR 
view at http://localhost/logs

7. Restart the pod by scaling instances down to 0 and back up.

% kubectl scale deployment hello --replicas=0
% kubectl get pods // ensure the pod is gone
% kubectl scale deployment hello --replicas=1

8. Add another log event.

% curl http://localhost/hello 
  OR 
view at http://localhost/hello

9. Verify the log has two entries.

% curl http://localhost/logs 
  OR 
view at http://localhost/logs

10. Clean up.

% kind delete cluster --name=hello-cluster
% docker image rm hello-app

References

• Docker Go Image Building
• Kind Quick Start
• Persistent Volumes
• Restarting Pods
• Kind Ingress