hello-kubernetes

Hello Kubernetes

This project studies the provisioning of interconnected applications ("microservices") as Docker containers and their deployment to Kubernetes.

It has three subprojects, each containing a microservice:

• backend-spring: A trival "hello" Spring Boot application that echos the path part of its URL. For example, when called like http://localhost/World, it replies with "[SPRING] Hello World".
• backend-golang: Identical to backend-spring, but written in Go.
• frontend-nodejs: A node.js "frontend" service that forwards path argument of its URL to the "backend" services backend-spring and backend-golang, collects the results, and returns them.

Preconditions

You need running Docker and Kubernetes installations, either on your workstation or at a public cloud provider.

For example, both Docker and Kubernetes come with Docker Desktop available for Mac and Windows. An alternative is minikube, which also runs on Linux.

If you decide for a public cloud provider, you can use their managed Kubernetes offers, or setup a Kubernetes cluster with Rancher.

Build Docker Images

Note: You can omit this step if you are interested in Kubernetes only. All images are available at Docker Hub in repository mouton4711/kubernetes.

$ sh build-images.sh

Deploy to Kubernetes

$ kubectl create configmap translation-config --from-literal=greetingLabel=Hello # Create config map from literals
$ kubectl apply -f ./backend-spring/kubernetes.yml
$ kubectl apply -f ./backend-golang/kubernetes.yml
$ kubectl apply -f ./frontend-nodejs/kubernetes.yml

Alternatively (and preferably!) you can combine all yaml files using the "kustomize" flag -k and deploy everything together:

$ kubectl apply -k .

The services backend-spring and backend-golang do not expose their endpoints to the outside (they use the default service type ClusterIP).

Service frontend-nodejs has type LoadBalancer. If you run Docker Desktop, there is nothing additional to do, because Docker Deskop exposes services of type LoadBalancer to localhost. You should be able to access the application from a web browser

curl -s http://localhost/World

If your Kubernetes runs on a public cloud, you need to create an Ingress service that connects to the cloud provider's load balancer. Alternatively, you can setup an own load balancer like ingress-nginx. If you manage your Kubernetes cluster with Rancher, you can provision an ingress service using the Rancher UI.

Extras

Change greeting language:

$ kubectl edit configmap translation-config
# Change the value of "greetingLabel" and save
$ kubectl rollout restart deployment backend-spring backend-golang frontend-nodejs