Expose pods: Creating Nodeport service

Networking in Kubernetes it´s not a simple matter but it is possible to advance a little beginning for a simple step: expose the pods, and make it accessible from a web browser.

Pods with nginx servers created in the last article are in a subnet different not the 192.168.0.X used in the previous examples ...Why??

So we have pods running nginx in a flat, cluster-wide, address space. In theory, you could talk to these pods directly, but what happens when a node dies? The pods die with it, and the ReplicaSet inside the Deployment will create new ones, with different IPs. This is the problem a Service solves.

A Kubernetes Service is an abstraction that defines a logical set of Pods running somewhere in your cluster, that all provide the same functionality. When created, each Service is assigned a unique IP address (also called clusterIP). This address is tied to the lifespan of the Service, and will not change while the Service is alive. Pods can be configured to talk to the Service, and know that communication to the Service will be automatically load-balanced out to some pod that is a member of the Service.

Steps to access the POD from outside the cluster using Nodeport

Create a Kubernetes pod

For instance, we create an Nginx pod and try to access it outside the world.

create a YAML file using your favorite text editor

nginx sample yaml file.

apiVersion: v1
kind: Pod
metadata:
  name: nginx
  labels:
    name: nginx
spec:
  containers:
  - name: nginx
    image: nginx

nginx.yaml

*We tied pods with services using Labels.

create a pod using below comment
```
kubectl create -f <filename.yaml>
```
To check pod is created or not.
```
kubectl get pod
```

Create a service yaml file for ngnix using nodeport

To create a service.yaml file.

    apiVersion: v1
    kind: Service
    metadata:
      name: nginx
      labels:
        name: nginx
    spec:
      type: NodePort
      ports:
        - port: 80
          nodePort: 30080
          name: http
        - port: 443
          nodePort: 30443
          name: https
      selector:
        name: nginx

The service.yaml file we used Nodeport as a 30080.

*Nodeport range: 30,000 TO 32767

The selector work here is to choose a specific pod among many pods, so here we give the Nginx pod labels name so selector only chooses Nginx pod.

Create a service file.
```
kubectl create -f service.yaml
```

To check service is created or not use below cmd.

 kubectl get svc

 NAME            TYPE           CLUSTER-IP     EXTERNAL-IP                                           PORT(S)                      AGE
 kubernetes      ClusterIP      10.43.0.1      <none>                                                443/TCP                      29h
 nginx           NodePort       10.43.58.151   <none>                                                80:30080/TCP,443:30443/TCP   7m49s
 nginx-project   LoadBalancer   10.43.83.4     192.168.0.80,192.168.0.81,192.168.0.82,192.168.0.83   80:30751/TCP                 54m

To cross-check the Nodeport you must describe the svc using below cmd.

kubectl describe svc <servicename>

Name:                     nginx
Namespace:                default
Labels:                   name=nginx
Annotations:              <none>
Selector:                 name=nginx
Type:                     NodePort
IP Family Policy:         SingleStack
IP Families:              IPv4
IP:                       10.43.58.151
IPs:                      10.43.58.151
Port:                     http  80/TCP
TargetPort:               80/TCP
NodePort:                 http  30080/TCP
Endpoints:                10.42.2.7:80
Port:                     https  443/TCP
TargetPort:               443/TCP
NodePort:                 https  30443/TCP
Endpoints:                10.42.2.7:443
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

Verification:

Open the web browser from the local machine and access type the Kubernetes node IP (one of the external ip provided by load balancer) along with the Node port (30080 in this example).

We are able to access the Nginx homepage successfully. It’s a containerized web server listening in the port 80 and we mapped it to 30080 in every node in the cluster.

browser