如何从节点 ip 开始使用 docker 运行访问容器

Question

I have one web application which I am trying to run on k8s cluster. I build the image from DockerFile and was testing locally till now using the command:

docker run --name web-app -d -p 8888:80 web-app

and I was able to access the GUI using http://localhost:8888.

Now, I am trying to run it in k8s cluster, so I executed the same docker run command in my k8s cluster and I am getting the o/p when I am trying to curl http://localhost:8888 from my cluster. But this is not I want in production, I want to access the web application using node ip like http://<node_ip>:8888. I tried a few times but not able to access it using node ip.

Now, I have 2 questions:

1. What changes I need to make in docker run command in order to access the application using node IP?
2. I also tried running the container using helm charts and by creating a service of type NodePort but it is also not working. Is there anything we need to take care while running any frontend web application using helm install?

Answer 1

For NodePort type service, you need to hit in <node_ip>:<nodePort> . NodePort is the port which you have exposed in you service maniest.

• kubectl get nodes -o wide : To get the NodeIP

For example, in this service manifest the nodePort is 31000 . Remember one thing nodePort range is from 30000 to 32767.

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  type: NodePort
  ports:
    - port: 80
      targetPort: 80
      nodePort: 31000

You don't need docker run if you deploy your application in kube.netes. Have you created a deployment of your application in k8s? If yes then you can enter your application via kubectl exec -it <pod_nam> sh . If you want to communicate from outside the cluster you need to create se NodePort type service as i said and then you can get the access by http://<node_ip>:<node_port> .

Here I have given a yaml for deployment as an example.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: nginx:1.14.1
          ports:
            - containerPort: 80

By the way, your containerPort in deployment must need to be equal to the targetPort in service.

Answer 2

it seems like you are trying with the wrong port. 8888 this is not a NodePort . NodePort range is (30000-32767) . better you look into the exact nodeport .

try this command kubectl get svc . output will be something like this.

kubectl get svc
NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP          17h
test-srv    NodePort    10.102.92.219   <none>        4000:31553/TCP   9s

For test-srv service, the nodeport is 31553 . And you can find your node's IP with

kubectl get nodes -o wide
NAME                 STATUS   ROLES    AGE   VERSION   INTERNAL-IP   EXTERNAL-IP   OS-IMAGE       KERNEL-VERSION     CONTAINER-RUNTIME
kind-control-plane   Ready    master   17h   v1.18.2   172.18.0.2    <none>        Ubuntu 19.10   5.8.0-41-generic   containerd://1.3.3-14-g449e9269

for me, nodeIp is 172.18.0.2 . Now just try with curl -k 172.18.0.2:31553 . The template is like <node_ip>:<node_port>