README.md

Services

Service - Kubernetes Services provide a way to expose an application running as a set of Pods. They provide a way to expose a set of Pods as a single logical service.

ServiceType - Every service has a type. The ServiceType determines how and where the service will expose your application. There are 4 service types:

• ClusterIP - Exposes a service which is only accessible from within the cluster.

• NodePort - Exposee a service via a static port on every node's IP, Expose to outside.

• LoadBalancer - Exposes a service via the cloud provider's load balancer.

• ExternalName - Exposes a service via an arbitrary name. (Outside the CKA scope)

• ClusterIP -

Create a deployment to try out a Service.

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: svc-example
  name: svc-example
  namespace: dev
spec:
  replicas: 3
  selector:
    matchLabels:
      app: svc-example
  strategy: {}
  template:
    metadata:
      labels:
        app: svc-example
    spec:
      containers:
      - image: nginx
        name: nginx
        ports:
          - containerPort: 80
status: {}

Then create the ClusterIP service.

apiVersion: v1
kind: Service
metadata:
  labels:
    app: svc-cluster-ip
  name: svc-cluster-ip
  namespace: dev
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80
  selector:
    app: svc-cluster-ip
  type: ClusterIP

Create the NodePort service.

apiVersion: v1
kind: Service
metadata:
  labels:
    app: svc-nodeport
  name: svc-nodeport
  namespace: dev
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80
    nodePort: 30080
  selector:
    app: svc-nodeport
  type: NodePort

Discovering Services with DNS

K8s DNS assign DNS names to Services, allowing application within the cluster to easily locate them.

A service's fully qualified domain name has the following format:

service-name.namespace.svc.cluster.cluster-domain.example

The default cluster domain is cluster.local.

K8s Ingress

Ingress is a declarative configuration for routing traffic to services.

kubectl create ingress my-ingress --rule=local/api/v1=my-service:8080 --dry-run=client -o yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-ingress
  namespace: dev
spec:
  rules:
  - host: local
    http:
      paths:
      - backend:
          service:
            name: my-service
            port:
              number: 8080
        path: /api/v1
        pathType: Exact
status:
  loadBalancer: {}