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CREATE-KUBERNETES-SERVICE.MD

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Create the Kubernetes Service for our Deployment

The Service load balances requests across the Pods. Remember that the pods are ephemeral. So if one of them stops, the ReplicaSet will create a replacement, but that Pod will have a different IP address. For that reason, clients should not communicate directly with the application in a Pod. Instead clients should talk to applications via their service.

Write the Service Specification

The service.yaml is where you specify the selector for the backend pods along with other specifications

apiVersion: v1
kind: Service
metadata:
  labels:
    app: daytrader-web
  name: daytrader-web
  namespace: default
spec:
  ports:
  - port: 443
    protocol: TCP
    targetPort: 5443
  selector:
    app: daytrader-web
  sessionAffinity: None
  type: ClusterIP

Create the Service Resource

  1. $ kubectl apply -f service.yaml

  2. $ kubectl get services

    NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
    daytrader-web ClusterIP 10.7.254.225 <none> 443/TCP 23s

    The above command creates a service resource. This resource listens on the CLUSTER IP and PORT. It is backed by endpoints to one or more pods. You can see the enpoints buy doing kubectl get endpoints. When the service receives an HTTPS request, it selects one of the endpoints (pods) and forwards the HTTPS request to the pod. The application running inside the pod handles the request and returns an HTTPS response.

    See also Kubernetes Concepts - Services, Load Balancing, and Networking

Test the Service Connection

  1. Start the proxy to locate and authenticate to the API Server.

    $ kubectl proxy

    You should see Starting to serve on 127.0.0.1:8001

    If you see a port binding error, start the proxy on a different port, e.g.

    $ kubectl proxy --port=8002

  2. Test the connection using the curl command

    $ curl -k http://localhost:8001/api/v1/namespaces/default/services/https:daytrader-web:/proxy/health

    You should see {"status":"UP"}

    The above curl command sends the HTTP request (without any authentication headers) to the proxy that is running on your local machine. The proxy, then, sends an HTTPS request with appropriate authentication headers to the API server. This is the easiest way to connect to the API server.

  3. See also Access Clusters Using the Kubernetes API