Kubernetes Services

Step-01: Introduction to Services¶

Service Types
ClusterIp
NodePort
LoadBalancer
ExternalName
Ingress
We are going to look in to ClusterIP and LoadBalancer Service in this section with a detailed example.
LoadBalancer Type is primarily for cloud providers and it will differ cloud to cloud, so we will do it accordingly (per cloud basis)
ExternalName doesn't have Imperative commands and we need to write YAML definition for the same, so we will look in to it as and when it is required in our course.

Step-02: ClusterIP Service - Backend Application Setup¶

Create a deployment for Backend Application (Spring Boot REST Application)

Create a ClusterIP service for load balancing backend application.

# Create Deployment for Backend Rest App
kubectl create deployment my-backend-rest-app --image=stacksimplify/kube-helloworld:1.0.0 
kubectl get deploy

# Create ClusterIp Service for Backend Rest App
kubectl expose deployment my-backend-rest-app --port=8080 --target-port=8080 --name=my-backend-service
kubectl get svc
Observation: We don't need to specify "--type=ClusterIp" because default setting is to create ClusterIp Service.

Important Note: If backend application port (Container Port: 8080) and Service Port (8080) are same we don't need to use --target-port=8080 but for avoiding the confusion i have added it. Same case applies to frontend application and service.
Backend HelloWorld Application Source kube-helloworld

Step-03: LoadBalancer Service - Frontend Application Setup¶

We have implemented LoadBalancer Service multiple times so far (in pods, replicasets and deployments), even then we are going to implement one more time to get a full architectural view in relation with ClusterIp service.
Create a deployment for Frontend Application (Nginx acting as Reverse Proxy)
Create a LoadBalancer service for load balancing frontend application.
Important Note: In Nginx reverse proxy, ensure backend service name my-backend-service is updated when you are building the frontend container. We already built it and put ready for this demo (stacksimplify/kube-frontend-nginx:1.0.0)

Nginx Conf File

server {
    listen       80;
    server_name  localhost;
    location / {
    # Update your backend application Kubernetes Cluster-IP Service name  and port below      
    # proxy_pass http://<Backend-ClusterIp-Service-Name>:<Port>;      
    proxy_pass http://my-backend-service:8080;
    }
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /usr/share/nginx/html;
    }
}

Docker Image Location: https://hub.docker.com/repository/docker/stacksimplify/kube-frontend-nginx

Frontend Nginx Reverse Proxy Application Source kube-frontend-nginx

# Create Deployment for Frontend Nginx Proxy
kubectl create deployment my-frontend-nginx-app --image=stacksimplify/kube-frontend-nginx:1.0.0 
kubectl get deploy

# Create LoadBalancer Service for Frontend Nginx Proxy
kubectl expose deployment my-frontend-nginx-app  --type=LoadBalancer --port=80 --target-port=80 --name=my-frontend-service
kubectl get svc

# Get Load Balancer IP
kubectl get svc
http://<External-IP-from-get-service-output>/hello
curl http://<External-IP-from-get-service-output>/hello

# Scale backend with 10 replicas
kubectl scale --replicas=10 deployment/my-backend-rest-app

# Test again to view the backend service Load Balancing
http://<External-IP-from-get-service-output>/hello
curl http://<External-IP-from-get-service-output>/hello

Step-04: Clean-Up Kubernetes Deployment and Services¶

# List Services
kubectl get svc 

# Delete Services
kubectl delete service my-backend-service 
kubectl delete service my-frontend-service 

# List Deployments
kubectl get deploy

# Delete Deployments
kubectl delete deployment my-backend-rest-app   
kubectl delete deployment my-frontend-nginx-app