Access NodePort Service Outside Kubeadm K8S Cluster

Question

I have two Ubuntu VMs created using Oracle Virtual Box on my Windows 11 laptop. I setup a k8s cluster using kubeadm with these two Ubuntu VMs, one of them is a master node and an another one is a worker node. Both the nodes are running with Ubuntu 20.04.3 LTS and docker://20.10.7. I deployed my spring boot app into the k8s cluster and exposed a node port service for my spring boot app with port 30000, but I am not really sure on how to access my node port service on the internet outside my cluster. Could you please help me with this issue?

Following are the IP address of my nodes in k8s cluster - master [192.168.254.94] and worker [192.168.254.95]. I tried with the following urls but none of them worked

http://192.168.254.94:30000/swagger-ui.html http://192.168.254.95:30000/swagger-ui.html

These above urls throwing message which says refused to connect

http://192.168.9.13:30000/swagger-ui.html http://192.168.9.14:30000/swagger-ui.html

These above urls says that the site cannot be reached

Below is the content of my application.yaml which I used for deploying the spring boot app and its corresponding service

apiVersion: apps/v1
kind: Deployment
metadata:
   name: dealer-engine
spec:
   replicas: 1
   selector:
      matchLabels:
         app: dealer-engine
   template:
      metadata:
        labels:
           app: dealer-engine
      spec:
         containers:
            - name: dealer-engine
              image: moviepopcorn/dealer_engine:0.0.1
              ports:
                 - containerPort: 9090
              env:
                 - name: MONGO_URL
                   value: mongodb://mongo-service:27017/mazda
              imagePullPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
   name: dealer-engine
spec:
   type: NodePort
   selector:
      app: dealer-engine
   ports:
      - port: 9091
        targetPort: 9090
        nodePort: 30000
   externalIPs:
    - 10.0.0.12

I am a beginner in k8s so please help me on how I can access my node port service outside my k8s cluster.

Answer 1

I created a new simple Springboot application which returns "Hello world!!!" back to the user when the following endpoint "/helloWorld" is invoked. I deployed this spring boot app into my k8s cluster using the below yaml configuration

apiVersion: apps/v1
kind: Deployment
metadata:
   name: hello-world
spec:
   replicas: 1
   selector:
      matchLabels:
         app: hello-world
   template:
      metadata:
        labels:
           app: hello-world
      spec:
         containers:
            - name: hello-world
              image: moviepopcorn/hello_world:0.0.1
              ports:
                 - containerPort: 9091
              imagePullPolicy: Always
---
apiVersion: v1
kind: Service
metadata:
   name: hello-world
spec:
   type: NodePort
   selector:
      app: hello-world
   ports:
      - port: 9091
        targetPort: 9091
        nodePort: 30001

After successful deployment, I am able to access the helloWorld endpoint using the following url <K8S_MASTER_NODE_IP>:<NODE_PORT (30001)>.

Thank you all for your answers and inputs. Very much appreciated.

Answer 2

Have you install any CNI plugin like flannel?

If yes, Check your CIDR setting here

kubectl get node k8s-master -o yaml | grep podCIDR:
kubectl get configmap -n kube-system kube-flannel-cfg -o yaml | grep '"Network":'

Basically yes, CNI is must. flannel is the most simple one.

https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/#pod-network

You must deploy a Container Network Interface (CNI) based Pod network add-on so that your Pods can communicate with each other. Cluster DNS (CoreDNS) will not start up before a network is installed.

1. Download cni pulgin on every server.

# download cni plugin
wget https://github.com/containernetworking/plugins/releases/download/v0.9.1/cni-plugins-linux-amd64-v0.9.1.tgz
sudo mkdir -p /opt/cni/bin
sudo tar -xzvf cni-plugins-linux-amd64-v0.9.1.tgz -C /opt/cni/bin

2. Reset you cluster

kubeadm reset

3. Init your cluster with cidr setting must same as flannel config, default 10.244.0.0

kubeadm init --pod-network-cidr=10.244.0.0/16

4. Apply cni plugin.

kubectl apply -f https://raw.githubusercontent.com/flannel-io/flannel/master/Documentation/kube-flannel.yml