Local kubernetes Hello World in nodejs with Docker - docker

Question

I've been following tutorial videos and trying to understand to build a small minimalistic application. The videos I followed are pulling containers from the registries while I'm trying to test, build and deploy everything locally at the moment if possible. Here's my setup.
I've the latest docker installed with Kubernetes enabled on mac OS.
A helloworld NodeJS application running with Docker and Docker Compose
TODO: I'd like to be able to start my instances, let's say 3 in the kubernetes cluster
Dockerfile
FROM node:alpine
COPY package.json package.json
RUN npm install
COPY . .
CMD ["npm", "start"]
docker-compose.yml
version: '3'
services:
user:
container_name: users
build:
context: ./user
dockerfile: Dockerfile
Creating a deployment file with the help of this tutorial and it may have problems since I'm merging information both from youtube as well as the web link.
Creating a miminalistic yml file for to be able to get up and running, will study other aspects like readiness and liveness later.
apiVersion: v1
kind: Service
metadata:
name: user
spec:
selector:
app: user
ports:
- port: 8080
type: NodePort
Please review the above yml file for correctness, so the question is what do I do next?

Answer 1

The snippets you provide are regrettably insufficient but you have the basics.
I had a Google for you for a tutorial and -- unfortunately -- nothing obvious jumped out. That doesn't mean that there isn't one, just that I didn't find it.
You've got the right idea and there are quite a few levels of technology to understand but, I commend your approach and think we can get you there.
Let's start with a helloworld Node.JS tutorial
https://nodejs.org/en/docs/guides/getting-started-guide/
Then you want to containerize this
https://nodejs.org/de/docs/guides/nodejs-docker-webapp/
For #3 below, the last step here is:
docker build --tag=<your username>/node-web-app .
But, because you're using Kubernetes, you'll want to push this image to a public repo. This is so that, regardless of where your cluster runs, it will be able to access the container image.
Since the example uses DockerHub, let's continue using that:
docker push <your username>/node-web-app
NB There's an implicit https://docker.io/<your username>/node-web-app:latest here
Then you'll need a Kubernetes cluster into which you can deploy your app
I think microk8s is excellent
I'm a former Googler but Kubernetes Engine is the benchmark (requires $$$)
Big fan of DigitalOcean too and it has Kubernetes (also $$$)
My advice is (except microk8s and minikube) don't ever run your own Kubernetes clusters; leave it to a cloud provider.
Now that you have all the pieces, I recommend you just:
kubectl run yourapp \
--image=<your username>/node-web-app:latest \
--port=8080 \
--replicas=1
I believe kubectl run is deprecated but use it anyway. It will create a Kubernetes Deployment (!) for you with 1 Pod (==replica). Feel free to adjust that value (perhaps --replicas=2) if you wish.
Once you've created a Deployment, you'll want to create a Service to make your app accessible (top of my head) this command is:
kubectl expose deployment/yourapp --type=NodePort
Now you can query the service:
kubectl get services/yourapp
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
yourapp NodePort 10.152.183.27 <none> 80:32261/TCP 7s
NB The NodePort that's been assigned (in this case!) is :32261 and so I can then interact with the app using curl http://localhost:32261 (localhost because I'm using microk8s).
kubectl is powerful. Another way to determine the NodePort is:
kubectl get service/yourapp \
--output=jsonpath="{.spec.ports[0].nodePort}"
The advantage of the approach of starting from kubectl run is you can then easily determine the Kubernetes configuration that is needed to recreate this Deployment|Service by:
kubectl get deployment/yourapp \
--format=yaml \
> ./yourapp.deployment.yaml
kubectl get service/yourapp \
--format=yaml \
> ./yourapp.service.yaml
These commands will interrogate the cluster, retrieve the configuration for you and pump it into the files. It will include some instance data too but the gist of it shows you what you would need to recreate the deployment. You will need to edit this file.
But, you can test this by first deleting the deployment and the service and then recreating it from the configuration:
kubectl delete deployment/yourapp
kubectl delete service/yourapp
kubectl apply --filename=./yourapp.deployment.yaml
kubectl apply --filename=./yourapp.service.yaml
NB You'll often see multiple resource configurations merged into a single YAML file. This is perfectly valid YAML but you only ever see it used by Kubernetes. The format is:
...
some: yaml
---
...
some: yaml
---
Using this you could merge the yourapp.deployment.yaml and yourapp.service.yaml into a single Kubernetes configuration.