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Kubernetes - Services

Step-01: Introduction to Services

  • Service Types
  • ClusterIp
  • NodePort
  • LoadBalancer
  • ExternalName
  • We are going to look in to ClusterIP and NodePort 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: NodePort Service - Frontend Application Setup

  • We have implemented NodePort 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 NodePort 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 
    # 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 ClusterIp Service for Frontend Nginx Proxy
kubectl expose deployment my-frontend-nginx-app  --type=NodePort --port=80 --target-port=80 --name=my-frontend-service
kubectl get svc

# Capture IP and Port to Access Application
kubectl get svc
kubectl get nodes -o wide
http://<node1-public-ip>:<Node-Port>/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://<node1-public-ip>:<Node-Port>/hello

Pending Topics

  • We will look in tho these items when we progress in to course on that respective cloud provider
  • LoadBalancer
  • ExternalName

AWS EKS - Elastic Kubernetes Service - Masterclass

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