Ingress Nginx inject subpath to root URI

Question

I'm trying to do the following uri manipulation in the Ingress-Nginx controller ( helm.sh/chart=ingress-nginx-4.2.0 )

If the URI is exactly / , pass https://example.com/ -to-> https://backend_server/devportal/

But if the URI matches this pattern (/a|/b|/c) , then just forward to https://backend_server/a|b|c

The seemingly simple requirement worked like this in an Nginx config:

server {
  listen       *:443 ssl; # Listen on port 443 
  location / {
    proxy_pass            https://backend_server/devportal/;
    proxy_redirect        https://backend_server/devportal/ /;
    # proxy_cookie_path     /devportal /;
  }
  location ~ (/a|/b|/c) {
    proxy_pass      https://backend_server;
    proxy_redirect  https://backend_server/devportal/ /;
  }
}

Which I can't replicate on ingress-nginx . I tried the following:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    kubernetes.io/ingress.class: nginx
    nginx.ingress.kubernetes.io/backend-protocol: HTTPS
    nginx.ingress.kubernetes.io/proxy-connect-timeout: 90s
    nginx.ingress.kubernetes.io/proxy-read-timeout: 90s
    nginx.ingress.kubernetes.io/proxy-redirect-from: /devportal/
    nginx.ingress.kubernetes.io/proxy-redirect-to: /
    nginx.ingress.kubernetes.io/proxy-send-timeout: 90s
    nginx.ingress.kubernetes.io/rewrite-target: /devportal/$1
    # nginx.ingress.kubernetes.io/app-root: /devportal
  name: multitenancy-ingress
  namespace: wso2
spec:
  rules:
  - host: example.com
    http:
      paths:
      - backend:
          service:
            name: my-svc
            port:
              name: servlet-https
        path: /(.*)
        pathType: ImplementationSpecific
  tls:
  - hosts:
    - example.com
    secretName: my-tls

When going to https://example.com/ , the backend application receives a / request ( GET / HTTP/1.1 302 )

1. Why isn't the rewrite working
2. How would I cater for both use-cases in the ingress object

Answer 1

Did you try to use nginx.ingress.kube.netes.io/stream-snippet annotation for ingress?

Can you try to use the working configuration by using this annotation like the in the docs: https://github.com/kube.netes/ingress-nginx/blob/main/docs/user-guide/nginx-configuration/annotations.md#stream-snippet