How To Associate Pod With Service In Kubernetes

Answer is to use selector

apiVersion: v1
kind: Service
metadata:
  name: mysql-service
  labels:
    app: mysql
spec:
    selector:
      app: mysql
    ports:
      - port: 3306
        targetPort:  3306
        nodePort:  30301
    clusterIP: None

This specification will create a Service which targets TCP port 3306 on  Pods with the app: mysql label,  in other words, any pods with label  app:mysql  would be associated with this mysql-service automatically in Kubernetes