Process to expose application using the Kubernetes NodePort type service object

NodePort - Exposes the Service on the same port of each selected Node in the cluster using NAT. It Makes a Service accessible from outside the cluster using :. Superset of ClusterIP.

How to create NodePort?
NodePort can be created by specifying a type in specs while creating Service object.For example, you have a node with IP address 172.18.0.6 and a spring-deployment pod running under it. NodePort will expose 172.18.0.6:30005, assuming the port exposed is 30005, which you can then access outside the Kubernetes cluster.

Example

apiVersion: v1
kind: Service
metadata:
  name: spring-service
spec:
  type: NodePort 
  selector:
    app: spring-app
  ports:
    - protocol: TCP
      port: 8081
      targetPort: 8081
      nodePort: 30005

note: The range of node port is 30000-32767

Let's expose our deployment created previously in NodePort type service.Here we will only change spec type as NodePort and assign nodePort as 30005. If we do not specify nodePort value service object will automatically assign from the range 30000-32767.

Let's modify our deploy-service.yaml created in the last blog.

vim deploy-service.yaml

Output

apiVersion: v1
kind: Service
metadata:
  creationTimestamp: null
  labels:
    app: spring-service
  name: spring-service
spec:
  type: NodePort
  ports:
   - nodePort: 30005
     port: 8081
     protocol: TCP
     targetPort: 8081
  selector:
    app: spring-service


---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-deployment
spec:
  replicas: 3 
  selector:
    matchLabels:
      app: spring-service
  template:
    metadata:
      labels:
        app: spring-service
    spec:
      containers:
      - name: demo-springapp
        image: jeewangautam02261995/springbootapp:v2

In this file below changes are made.
type as NodePort and added nodePort as 30005

Let's apply this changes and run below command to verify service type.

kubectl get svc -l app=spring-service

Result

you can see, spring-service is. NodePort type assigned IP 10.96.89.35 and which will listen port '30005' and forward the traffic to pod's port '8081'.

Let's try to access our application from one of the master node as we deployed application in multi-node cluster architecture.

let's list out all the nodes first.

kubectl get nodes

Result

There are 3 master nodes and 5 worker nodes but we deploy application in 3 replicas so let’s filter it out using pod's labels.

kubectl get pods  -l app=spring-service -o wide

Result

From above command you can see application is deployed in spring-app-worker spring-app-worker3 spring-app-worker5. Now we will access application from spring-app-control-plane master node.

Run below command to access master node first.

docker exec -it spring-app-control-plane sh

Docker command is used here to access master node because kind cluster runs in the docker container.

Result

Let's use ip address of spring-app-worker3 which is 10.244.7.4 and user curl command. syntax is given below.

Syntax

curl http://<nodeIP>:<nodeport>

Example

curl http://172.18.0.5:30005

Result

We can see, Application is accessible.

In the next blog, we will discuss how to create LoadBalancer type service locally in Kind and expose it to the external user.