Is it possible to rewrite HOST header in k8s Ingress Controller? - nginx

Question

Due to some legacy application that relies on Host header to function correctly, I need to have an Ingress (proxy, etc) that capable of rewrite Host header and pass that to downstream (backend). Is there any Ingress Controller that supports this functionality?
Example:
End user access our website through foo.com/a for backend a and foo.com/b for backend b. But since a and b are legacy app, it only accept:
a accepts connection when Host: a.foo.com
b accepts connection when Host: b.foo.com

Answer 1

This can be done using this annotation: nginx.ingress.kubernetes.io/upstream-vhost: host.example.com

Answer 2

I'm not sure whether you can find appropriate annotation within NGINX Ingress Controller for Host header modification to match your requirement as well. However, you can consider using nginx.ingress.kubernetes.io/configuration-snippet annotation in order to append configuration snippet to the location block inside nginx.conf of the particular Nginx controller pod:
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
annotations:
kubernetes.io/ingress.class: nginx
nginx.ingress.kubernetes.io/configuration-snippet: |
proxy_set_header Host www.example-host.com;
name: my-app
spec:
rules:
- host: my-app.example.com
http:
paths:
- backend:
path: /app
serviceName: my-app
servicePort: http
We set here Host header www.example-host.com for target URL my-app.example.com.

Answer 3

I want to add my finding to this question of mine.
Although my solution is not using k8s Ingress Controller, our cluster is using Istio and Istio's VirtualService supports rewrite the uri and authority (Host header) as documented in this link: https://istio.io/docs/reference/config/istio.networking.v1alpha3/#HTTPRewrite
To know how I implement that in my case, you can take a look at this link: https://github.com/istio/istio/issues/11668

Answer 4

you can use ingress nginx controller on Kubernetes and set head and also transfer to backend and manage services connection from ingress objects.
here sharing link for rewrite target from header: https://kubernetes.github.io/ingress-nginx/examples/rewrite/
ingress nginx will be also good with SSL cert manager you can add it.
manage other thing using annotations of ingress.
check this out for ingress SSL setup you can modify it and per your need: https://www.digitalocean.com/community/tutorials/how-to-set-up-an-nginx-ingress-with-cert-manager-on-digitalocean-kubernetes
ingress will be like at last
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: ingress
annotations:
kubernetes.io/ingress.class: nginx
nginx.ingress.kubernetes.io/rewrite-target: /
spec:
tls:
- hosts:
- myapp.abc.com
secretName: ingress-tls
rules:
- host: myapp.abc.com
http:
paths:
- path: /my-service
backend:
serviceName: my-backend
servicePort: 80