Which ports needed to be set for a k8s deployment?-CodePudding

I do not understand how to configure ports correctly for a k8s deployment.

Assume there is a nextJS application which listens to port 3003 (default is 3000). I build the docker image:

FROM node:16.14.0
RUN apk add dumb-init

# ...

EXPOSE 3003

ENTRYPOINT ["/usr/bin/dumb-init", "--"]
CMD npx next start -p 3003

So in this Dockerfile there are two places defining the port value 3003. Is this needed?

Then I define this k8s manifest:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: example
spec:
    spec:
      containers:
        - name: example
          image: "hub.domain.com/example:1.0.0"
          imagePullPolicy: IfNotPresent
          ports:
            - containerPort: 3003
---
apiVersion: v1
kind: Service
metadata:
  name: example
spec:
  ports:
    - protocol: TCP
      port: 80
      targetPort: 3003
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example
  namespace: default
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt-prod
    kubernetes.io/ingress.class: nginx
    kubernetes.io/tls-acme: "true"
    nginx.ingress.kubernetes.io/ssl-passthrough: "true"
spec:
  tls:
    - hosts:
        - domain.com
      secretName: tls-key
  rules:
    - host: domain.com
      http:
        paths:
          - pathType: Prefix
            path: "/"
            backend:
              service:
                name: example
                port:
                  number: 80

The deployment is not working correctly. Calling domain.com shows me a 503 Service Temporarily Unavailable error.

If I do a port forward on the pod, I can see the working app at localhost:3003. I cannot create a port forward on the service.

So obviously I'm doing something wrong with the ports. Can someone explain which value has to be set and why?

CodePudding user response：

You are missing labels from the deployment and the selector from the service. Try this:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: example
  labels:
    app: example
spec:
  selector:
    matchLabels:
      app: example
  template:
    metadata:
      labels:
        app: example
    spec:
      containers:
        - name: example
          image: "hub.domain.com/example:1.0.0"
          imagePullPolicy: IfNotPresent
          ports:
            - containerPort: 3003
---
apiVersion: v1
kind: Service
metadata:
  name: example
spec:
  selector:
    app: example
  ports:
    - protocol: TCP
      port: 80
      targetPort: 3003
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example
  namespace: default
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt-prod
    kubernetes.io/ingress.class: nginx
    kubernetes.io/tls-acme: "true"
    nginx.ingress.kubernetes.io/ssl-passthrough: "true"
spec:
  tls:
    - hosts:
        - domain.com
      secretName: tls-key
  rules:
    - host: domain.com
      http:
        paths:
          - pathType: Prefix
            path: "/"
            backend:
              service:
                name: example
                port:
                  number: 80

Deployment: https://kubernetes.io/docs/concepts/workloads/controllers/deployment/

Service: https://kubernetes.io/docs/concepts/services-networking/service/

Labels and selectors: https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/

You can name your label keys and values anything you like, you could even have a label as whatever: something instead of app: example but these are some recommended labels: https://kubernetes.io/docs/concepts/overview/working-with-objects/common-labels/ https://kubernetes.io/docs/reference/labels-annotations-taints/