Services

Background

When we deploy an application and the pods is already running, we want to be able to access the application. But we can’t directly access the pods due to :

• Pods are often isolated in a private network of the cluster
• Pods IP is changing dynamically based on multiple trigger (no static IP)

Thus, we need a Service, a method for exposing a network application that is running as one or more Pods in your cluster. A key aim of Services in Kubernetes is that you don’t need to modify your existing application to use an unfamiliar service discovery mechanism.
You use a Service to make that set of Pods available on the network so that clients can interact with it.

Details

There are 4 types of Services in K8s, and we’re going to use NodePort. For other Service type, please refer to THIS We’re going to use NodePort because its simpler and works out of the box. We can append below config in the deployments.yaml:

[... Deployment detail]
---
apiVersion: v1
kind: Service
metadata:
  name: order-service
  annotations:
    prometheus.io/scrape: "true"
    prometheus.io/path: "/actuator/prometheus"
    prometheus.io/port: "9873"
spec:
  selector:
    app: order-service
  ports:
    - port: 9873
      targetPort: 9873
  type: NodePort

And to access, we can use command :

minikube service order-service --url

# http://127.0.0.1:55588 (sample output)