Reference nginx-ingress host name to internal service - kubernetes-ingress

Question

After creating all require resource and config the nginx-ingress controller.
apiVersion: apps/v1
kind: Deployment
metadata:
name: user-api
spec:
replicas: 1
selector:
matchLabels:
app: user-api
strategy: {}
template:
metadata:
labels:
app: user-api
spec:
dnsPolicy: ClusterFirstWithHostNet
hostNetwork: true
containers:
- name: user-api
image: doumeyi/user-api-amd64:1.0
ports:
- name: user-api
containerPort: 3000
resources: {}
---
apiVersion: v1
kind: Service
metadata:
name: user-api
spec:
selector:
app: user-api
ports:
- name: user-api
port: 3000
targetPort: 3000
type: LoadBalancer
---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: app-ingress
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /
spec:
rules:
- host: example.com
http:
paths:
- path: /user-api
backend:
serviceName: user-api
servicePort: 3000
I can view example.com show the 404 not found page, but also can not see example.com/user-api to show any message I build in user-api service.
It seems the nginx-ingress cannot resolve the host name to the internal service, how should I fix it?

Answer 1

If NGINX cannot find a route to your Pod, it should not respond with 404. Instead it should give an 502 (Bad Gateway) AFAIK. I assume the 404 is from your application.
NGINX-Ingress changed behavior in 0.22 as mentioned here
The ingress resource should look like this:
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: app-ingress
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /$2
spec:
rules:
- host: example.com
http:
paths:
- path: /user-api(/|$)(.*)
backend:
serviceName: user-api