Nodeport.md

Nodeport is used to expose a pod to the outside world from a containerize environemnt.

Suppose we have a service deployment file like this:

apiVersion: v1
kind: Service
metadata:
    name: posts-srv # will be identified as this service name for kubernetes service
spec:
    type: NodePort
    selector:
        app: posts # find this pod and expose this in the outside world
    ports:
        - name: posts
          protocol: TCP
          port: 4000 # Node port
          targetPort: 4000 # container port

when we will create the service using:

kubectl apply -f posts-srv.yaml

then a new service will be created.

as the file describes:

• NodePort is a kind of service that will give us access of a container running inside a pod from the browser in the host computer.
• the port in the ports section is the port of the node service which is running on a dedicated port.
• NodePort -> nodeport service port -> container port that we want to access.
• NodePort can be found here:

  • kubectl describe service posts-srv

  • result will be:

        Name:                     posts-srv
        Namespace:                default
        Labels:                   <none>
        Annotations:              <none>
        Selector:                 app=posts
        Type:                     NodePort
        IP Family Policy:         SingleStack
        IP Families:              IPv4
        IP:                       10.100.28.189
        IPs:                      10.100.28.189
        Port:                     posts  4000/TCP
        TargetPort:               4000/TCP
        NodePort:                 posts  30963/TCP
        Endpoints:                10.1.0.91:4000
        Session Affinity:         None
        External Traffic Policy:  Cluster
        Events:                   <none>

  • Nodeport is specified as NodePort in here.

In a windows or linux machine we can access out post container in this url:

http://localhost:30963/posts

because:

• the targetport is the container port for the nodeport to access from the browser. Quite confusing!
• look at the yaml file for service configuration and you will understand