k8s Practices

 

Deployment of Simple Nginx

• minikube status
• minikube start

• kubectl create deployment my-nginx --image=nginx:latest
• kubectl get deployments
• kubectl get pods
• minikube dashboard

Try http://localhost/

• kubectl expose deployment my-nginx --port=80 --type=LoadBalancer
• minikube service my-nginx

Try Again http://localhost/

• kubectl get pods
• kubectl delete deployment my-app

Demo Reactjs Webapp Project

Step 1) Setup Fresh React Project On local

Step 2) Craete Dockerfile

FROM node
WORKDIR /app/
COPY . .
RUN npm install
EXPOSE 3000
CMD ["npm", "start"]

Step 3) Build and deploy to Dockerhub

docker build -t subhash1583/webapp:V1
docker login
docker push subhash1583/webapp:V1

Step 4) Create Project

kubectl create deployment my-webapp --image=reponame/webapp-demo:V1
kubectl get deployments
kubectl get pods

Step 5) Exposing Port

kubectl expose deployment my-webapp --port=3000 --type=LoadBalancer

kubectl get services
minikube service my-webapp

Scaling our App

• kubectl scale deployment node-app --replicas=4
• kubectl get pods
• kubectl scale deployment node-app --replicas=2
• kubectl get pods

Rollout in K8

Make Changes in src/App.js

• docker build -t subhash1583/webapp:v3 .
• docker push subhash1583/webapp:v3

Map Docker image with kubernets so that latest docker build v3 get depolyed

• kubectl set image deployment my-webapp write-container-name=subhash1583/webapp:v3
• kubectl get pods

Rollback in K8

Map intentionally Wrong Docker image tag with kubernets

• kubectl set image deployment my-webapp write-container-name=subhash1583/webapp:v4
• kubectl get pods

Showing error status : ImagePullBackOff 

To Stop(Rollout) this

• kubectl rollout undo deployment my-webapp

Self-Healing in K8

Demo In local System:

https://drive.google.com/drive/folders/1PsUe7IV5BGoSN7ieiXMKzJ4gBOVgsJjM

npm i
node index.js

• http://localhost:3000/
• http://localhost:3000/exit

Demo With K8: Using Existing docker image to save time

• kubectl create deployment node-app --image=philippaul/node-demo-app:v1
• kubectl get deployment
• kubectl get pods

• kubectl expose deployment node-app --port=3000 --type=LoadBalancer
• minikube service node-app

• http://localhost:3000/
• http://localhost:3000/exit

• YAML config For Deployment: 1

https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.32/#deployment-v1-apps

vim deployment-node-app.yaml

apiVersion: apps/v1 kind: Deployment metadata: name: my-node-app spec: replicas: 3 selector: matchLabels: app: node-app template: metadata: labels: app: node-app spec: containers: - name: node-app #docker image with tag image: subhash1583/webapp:v6

• kubectl apply -f deployment-node-app.yaml
• kubectl get pods

vim deployment-node-app.yaml

Change Replica no (in up or down)

• kubectl apply -f deployment-node-app.yaml
• kubectl get pods

• YAML config For Services: 2

https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.32/#service-v1-core

vim service-node-app.yaml

apiVersion: v1 kind: Service metadata: name: service-my-node-app spec: selector: app: node-app ports: - protocol: TCP port: 8080 targetPort: 3000 type: LoadBalancer

• kubectl apply -f service-node-app.yaml
• minikube service service-my-node-app

Multiple containers in single POD

Not Configured Yet.

Multiple containers in Separate POD

https://drive.google.com/drive/folders/1Fqjxbf1N1BY-vTveAT-itnUCjsDZ-j0b?usp=sharing

* Changes in node project (Dynamic Host & Port For DB URL)

* Building image & pushing image with 03 version

vim index.js

• add :

const mongoHost = process.env.MONGO_HOST || 'localhost';
const mongoPort = process.env.MONGO_PORT || '27017';

• Replace from : mongoose.connect('mongodb://mongo:27017/yourDatabaseName'
• Replace this : mongoose.connect(`mongodb://${mongoHost}:${mongoPort}/yourDatabaseName`

• docker build --platform linux/amd64 -t subhash1583/node-mongo-db:v3 .
• docker push subhash1583/node-mongo-db:v3

First create combine deployment and service config file for MONGO APP so we will be having service name

vim mongo-db.yaml

apiVersion: apps/v1 kind: Deployment metadata: name: mongo-app spec: replicas: 1 selector: matchLabels: app: mongo-app template: metadata: labels: app: mongo-app spec: containers: - name: mongo-app image: mongo:latest --- apiVersion: v1 kind: Service metadata: name: service-mongodb spec: selector: app: mongo-app ports: - name: TCP port: 27017 targetPort: 27017

• kubectl apply -f mongo-db.yaml
• kubectl get pods

Now create deployment and service config for NODE APP and explain how to use env variables in config

vim node-app.yaml

apiVersion: apps/v1 kind: Deployment metadata: name: node-app spec: replicas: 2 selector: matchLabels: app: node-app template: metadata: labels: app: node-app spec: containers: - name: node-app image: subhash1583/node-mongo-db:v9 --- apiVersion: v1 kind: Service metadata: name: service-node-app spec: ports: - name: http port: 3000 targetPort: 3000 selector: app: node-app type: LoadBalancer

Now we will create configMAP file

vim mongo-config.yaml

apiVersion: v1 kind: ConfigMap metadata: name: mongo-config data: #map with the mongo-service file name as host MONGO_HOST: "service-mongodb" MONGO_PORT: "27017"

Now update Existing file Again

vim node-app.yaml

• From This:

spec:

containers:

- name: node-app

image: subhash1583/node-mongo-db:v9

• To This: 

spec:

containers:

- name: node-app

image: subhash1583/node-mongo-db:v9

env:

- name: MONGO_HOST

valueFrom:

configMapKeyRef:

name: mongo-config

key: MONGO_HOST

- name: MONGO_PORT

valueFrom:

configMapKeyRef:

name: mongo-config

key: MONGO_PORT

 Run node-app deployment

• kubectl apply -f mongo-config.yaml
• kubectl apply -f node-app.yaml
• minikube service service-node-app

Now Try:

• http://localhost:3000/
• http://localhost:3000/exit

Drawback: If the MongoDB pod is deleted, all stored data will be lost since Kubernetes pods are ephemeral.

Solution: To prevent data loss, we will configure Persistent Volumes (PV) and Persistent Volume Claims (PVC), ensuring data persists even if the pod is restarted or replaced.

• Create Persistent Volume

vim host-pv.yml

apiVersion: v1 kind: PersistentVolume metadata: name: host-pv spec: capacity: storage: 1Gi volumeMode: Filesystem storageClassName: standard accessModes: - ReadWriteOnce hostPath: path: /data/ type: DirectoryOrCreate

• Create Persistent Volume Claim

vim host-pvc.yml

apiVersion: v1 kind: PersistentVolume metadata: name: host-pv spec: capacity: storage: 1Gi volumeMode: Filesystem storageClassName: standard accessModes: - ReadWriteOnce hostPath: path: /data/ type: DirectoryOrCreate

Now update Existing file (to add the volume with mongo config)

• From This:

spec:

containers:

- name: mongo-app

image: mongo:latest

• To This: 

spec:

containers:

- name: mongo-app

image: mongo:latest

volumes:

- name: mongo-vol

persistentVolumeClaim:

claimName: host-pvc

Now update Existing file Again (to point the volume with mongo container)

• From This:

spec:

containers:

- name: mongo-app

image: mongo:latest

volumes:

- name: mongo-vol

persistentVolumeClaim:

claimName: host-pvc

• To This: 

spec:

containers:

- name: mongo-app

image: mongo:latest

volumeMounts:

- mountPath: /data/db

name: mongo-vol

volumes:

- name: mongo-vol

persistentVolumeClaim:

claimName: host-pvc

• kubectl apply -f host-pv.yml
• kubectl apply -f host-pvc.yml
• kubectl apply -f mongo-db.yml

• kubectl get pv
• kubectl get pvc

Delete All Setup

• kubectl delete pv pv-name
• kubectl delete pvc pvc-name
• kubectl delete deployment deployment-name
• kubectl delete service service-name