Kubernetes - Services 🛎️

Description 👀

A service is a way to expose an application running on a set of pods as a network service. It is services that enables connectivity between pods and external clients.

Types of Services 🟦🟩🟪

• NodePort
  • makes an internal port accessible on the node
  • uses three ports
  • one port on the node, the node port
    • the node ports range is between 30000-32767
  • one port on the pod, the target port
  • one port on the service, the service port
• ClusterIP
  • creates a virtual IP inside the cluster that allows other services to communicate with it
  • helps provide a single interface to a set of pods
• LoadBalancer
  • provisions a load balancer
    • only works on cloud providers that support native load balancers

More on ClusterIP ✨

CusterIP is used to expose a service to other pods in the cluster. It provides a single interface that other pods can use to access the service. This enables the ability to easily and efficiently scale the service by adding or removing pods as needed.

Creating a Service 🛠️

• basic service definition

  apiVersion: v1
  kind: Service
  metadata:
    name: webapp-service
  spec:
    type: NodePort
    ports:
      # only port is needed, other fields are optional 
      - targetPort: 8080
        port: 8080 # port on the service object
        nodePort: 30080 
    # selector is used to find the pods to route traffic to
    selector:
      name: simple-webapp
  

  what do you do when you have multiple pods?

  when the service is created, it will select all pods that match the selector and route traffic to them. No additional configuration is needed. 🌟 It’s magic. 🌟

Basic Commands 📝

• get list of services

kubectl get services

• get descriptive information on the desired service

kubectl describe service <service-name>

• access service in browser running on minikube

minikube service <service-name> --url

Examples 🧩

• sample NodePort service definition

  apiVersion: v1 
  kind: Service
  metadata:
    name: myapp-service
  spec:
    type: NodePort
    ports:
      - targetPort: 80
        port: 80
        nodePort: 30008
    selector:
      app: myapp
      type: front-end
  

• sample ClusterIP service definition

  apiVersion: v1
  kind: Service
  metadata:
    name: back-end
  spec:
    type: ClusterIP
    ports:
      - targetPort: 80
        port: 80
    selector:
      app: myapp
      type: back-end
  

• sample service for deployment with web-hooks

  apiVersion: v1
  kind: Service
  metadata:
    name: webhook-server
    namespace: webhook-demo
  spec:
    selector:
      app: webhook-server
    ports:
      - port: 443
        targetPort: webhook-api
  

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