Error Multipath Kubernetes Ingress, Cannot GET /-CodePudding

I'm trying to learn about multipath in Kubernetes Ingress. First of all, I'm using minikube for this tutorial, I created a simple Web API using node js.

NodeJS Code

In this nodeJS, I created a simple Web API, with routing and controller

server.js

const express = require ('express');
const routes = require('./routes/tea'); // import the routes

const app = express();

app.use(express.json());

app.use('/', routes); //to use the routes

const listener = app.listen(process.env.PORT || 3000, () => {
    console.log('Your app is listening on port '   listener.address().port)
})

routes/tea.js

const express = require('express');
const router  = express.Router();
const teaController = require('../controllers/tea');

router.get('/tea', teaController.getAllTea);
router.post('/tea', teaController.newTea);
router.delete('/tea', teaController.deleteAllTea);

router.get('/tea/:name', teaController.getOneTea);
router.post('/tea/:name', teaController.newComment);
router.delete('/tea/:name', teaController.deleteOneTea);

module.exports = router;

controllers/tea.js

const os = require('os');

//GET '/tea'
const getAllTea = (req, res, next) => {
    res.json({message: "GET all tea, "   os.hostname() });
};

//POST '/tea'
const newTea = (req, res, next) => {
    res.json({message: "POST new tea, "   os.hostname()});
};

//DELETE '/tea'
const deleteAllTea = (req, res, next) => {
    res.json({message: "DELETE all tea, "   os.hostname()});
};

//GET '/tea/:name'
const getOneTea = (req, res, next) => {
    res.json({message: "GET 1 tea, os: "   os.hostname()   ", name: "   req.params.name});
};

//POST '/tea/:name'
const newComment = (req, res, next) => {
    res.json({message: "POST 1 tea comment, os: "   os.hostname()   ", name: "   req.params.name});
};

//DELETE '/tea/:name'
const deleteOneTea = (req, res, next) => {
    res.json({message: "DELETE 1 tea, os: "   os.hostname()   ", name: "   req.params.name});
};

//export controller functions
module.exports = {
    getAllTea, 
    newTea,
    deleteAllTea,
    getOneTea,
    newComment,
    deleteOneTea
};

Dockerfile

After that I created a docker image using this Dockerfile

FROM node:18.9.1-slim
WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 3000
CMD [ "node", "server.js" ]

Kubernetes Manifest

And then, I created replicaset and service for this docker image

foo-replicaset.yaml

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: foo
spec:
  selector:
    matchLabels:
      app: foo
  replicas: 3
  template:
    metadata:
      labels:
        app: foo
    spec:
      containers:
        - name: foo
          image: emriti/tea-app:1.0.0
          ports:
            - name: http
              containerPort: 3000
              protocol: TCP

foo-svc-nodeport.yaml

apiVersion: v1
kind: Service
metadata:
  name: foo-nodeport
spec:
  type: NodePort
  ports:
    - port: 3000
      targetPort: 3000
      nodePort: 31234
  selector:
    app: foo

all-ingress.yaml

Ingress for both Foo and Bar backend

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: foobar
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /$1
spec:
  rules:
    - host: foobar.com
      http:
        paths:
          - path: /foo
            pathType: Prefix
            backend:
              service:
                name: foo-nodeport
                port:
                  number: 3000  
          - path: /bar
            pathType: Prefix
            backend:
              service:
                name: bar-nodeport
                port:
                  number: 3000

Additional setup

I also did these:

add 127.0.0.1 foobar.com to /etc/hosts
running minikube tunnel

After that I run curl foobar.com/foo/tea and I get this error:

curl : Cannot GET /
At line:1 char:1
  curl foobar.com/foo
  ~~~~~~~~~~~~~~~~~~~
      CategoryInfo          : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-WebRequest], WebException
      FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand

I'm wondering if maybe someone has experienced a similar problem that I did and maybe already had the answer for that. Secondly how to debug the ingress if I meet similar issues?

The codes and manifest could be accessed on this repo

Thank you!

CodePudding user response：

Your problem is here:

  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /$1

You haven't defined any capture groups in your rules, so this directive is rewriting all requests to /. If a client asks for /foo/tea/darjeeling, you request /. If a client requests /foo/this/does/not/exist, you request /.

To make this work, you need to add appropriate capture groups to your rules:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: foobar
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /$1
spec:
  rules:
    - host: foobar.com
      http:
        paths:
          - path: /foo/(.*)
            pathType: Prefix
            backend:
              service:
                name: foo-nodeport
                port:
                  number: 3000
          - path: /bar/(.*)
            pathType: Prefix
            backend:
              service:
                name: bar-nodeport
                port:
                  number: 3000

I suspect you would have found this much easier to debug if your application were to log incoming requests. You might want to look into that. I figured this by adding a sidecar proxy to your pods that would log requests, which made the problem relatively obvious (I could see that every request was for / regardless of what URL the client was using).

There's more documentation about path rewriting when using the Nginx ingress service here.

Unrelated to your question:

You probably want to update your manifests to create Deployment resources instead of ReplicaSets.
For the way you've configured things here you don't need NodePort services.