How to rewrite url to backend while preserving browser url in nginx ingress?

Question

I'm trying to rewrite the path to the service while preserving the browser url with nginx ingress on kubernetes.

What I need is this:

http://example.com/path => http://service
http://example.com/path/bar => http://service/bar
http://example.com/path/file.css => http://service/file.css

That is, make the /path be the root (or some different url) in the upstream server.

From what I see here, this is done using a trailing slash on the proxy_pass, but nginx ingress doesn't seem to have this option.

Is this possible nginx ingress?

score 8 · Answer 1 · answered May 18 '20 at 10:05

Is it Possible on Nginx Ingress?

Yes, In order to achieve it you can use rewrite-target.
It will create a capture group and send it to the appropriate service. Here is an Ingress example:

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: "rewrite"
  annotations:
    kubernetes.io/ingress.class: nginx
    nginx.ingress.kubernetes.io/rewrite-target: /$2
spec:
  rules:
    - http: example.com
        paths: 
          - path: /foo(/|$)(.*)
            backend:
              serviceName: echo-svc
              servicePort: 80

In this ingress definition, any characters captured by (.*) will be assigned to the placeholder $2, which is then used as a parameter in the rewrite-target annotation.

This ingress will do the following:

Requests to /foo will be delivered to echo1-svc as /
Requests to /foo/bar will be delivered to echo1-svc as /bar
Requests to /foo/file.css will be delivered to echo-svc as /file.css
Nginx Ingress uses Path Priority:

In NGINX, regular expressions follow a first match policy. In order to enable more accurate path matching, ingress-nginx first orders the paths by descending length before writing them to the NGINX template as location blocks.

Example:

$ kubectl apply -f echo-ingress.yaml 
ingress.networking.k8s.io/echo-ingress created

$ kubectl get ingress
NAME           HOSTS          ADDRESS        PORTS   AGE
echo-ingress   mydomain.com   35.188.7.149   80      48s

$ tail -n 1 /etc/hosts
35.188.7.149 mydomain.com

$ curl mydomain.com/foo/bar
{"path": "/bar",
...suppressed output...
  "os": {"hostname": "echo-deploy-764d5df7cf-6m5nz"}
}

$ curl mydomain.com/foo
{"path": "/",
  "os": {"hostname": "echo-deploy-764d5df7cf-6m5nz"}
}

If you have any question let me know in the comments.

good answer. note that ingress-nginx has to be installed in the cluster to work. also this is interesting to know how to go about multipath : https://github.com/kubernetes/ingress-nginx/issues/6139 (thus making two ingress yaml files). — Vincent Gerris, Feb 01 '21 at 17:59

score 0 · Answer 2 · answered Feb 01 '21 at 18:02

In short: yes it is. Make sure not to confuse nginx-ingress (which you use as a label in your question ) and ingress-nginx, those are different. It works with ingress-nginx by installing it according to documentation. The provided answer from @Will R.O.F. shows how and the documentation can be found here: https://kubernetes.github.io/ingress-nginx/user-guide/ingress-path-matching/

How to rewrite url to backend while preserving browser url in nginx ingress?

2 Answers2