How to capture subdomain in nginx ingress - nginx

Question

I want to capture subdomain and rewrite URL with /subdomain, For example bhautik.bhau.tk rewrite to bhau.tk/bhautik.
I also https://github.com/google/re2/wiki/Syntax tried group syntax
Here is my nginx ingress config:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: subdomain
namespace: subdomain
annotations:
kubernetes.io/ingress.class: nginx
nginx.ingress.kubernetes.io/use-regex: "true"
# nginx.ingress.kubernetes.io/rewrite-target: /$sub
nginx.ingress.kubernetes.io/server-snippet: |
set $prefix abcd;
if ($host ~ ^(\w+).bhau\.tk$) {
// TODO?
}
nginx.ingress.kubernetes.io/rewrite-target: /$prefix/$uri
spec:
rules:
- host: "*.bhau.tk"
http:
paths:
- pathType: Prefix
path: "/"
backend:
service:
name: subdomain
port:
number: 80
How do I capture subdomain from $host?

Answer 1

I believe you want a redirect instead of rewrite. Here is the server-snippet you need:
nginx.ingress.kubernetes.io/server-snippet: |
if ($host ~ ^(?<subdom>\w+)\.(?<basedom>bhau\.tk)$) {
return 302 https://$basedom/$subdom/ ;
}
If you really want a rewrite where the URL that the user sees remains unchanged but instead the request will be routed to a subpath served by the same service:
nginx.ingress.kubernetes.io/server-snippet: |
if ($host ~ ^(?<subdom>\w+)\.(?<basedom>bhau\.tk)$) {
rewrite ^/(.*)$ /$subdom/$1 ;
}
Remove the rewrite-target annotation that specifies $prefix. You don't need it.
The ?<capturename> and $capturename pair is the trick you are looking for.

Answer 2

You can try out the
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
annotations:
nginx.ingress.kubernetes.io/rewrite-target: /$2
nginx.ingress.kubernetes.io/server-snippet: |
if ($host ~ "bhautik.bhau.tk")
{
rewrite ^ https://bhau.tk$host permanent;
}
name: test-ingress
spec:
rules:
- host: bhau.tk
http:
paths:
- backend:
serviceName: app-service
servicePort: 3000
path: (/|$)(.*)