ingress-nginx-helm/docs/user-guide/ingress-path-matching.md

Ingress Path Matching

Regular Expression Support

!!! important Regular expressions and wild cards are not supported in the spec.rules.host field. Full hostnames must be used.

The ingress controller supports case insensitive regular expressions in the spec.rules.http.paths.path field. This can be enabled by setting the nginx.ingress.kubernetes.io/use-regex annotation to true (the default is false).

!!! hint Kubernetes only accept expressions that comply with the RE2 engine syntax. It is possible that valid expressions accepted by NGINX cannot be used with ingress-nginx, because the PCRE library (used in NGINX) supports a wider syntax than RE2. See the RE2 Syntax documentation for differences.

See the description of the use-regex annotation for more details.

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress
  annotations:
    nginx.ingress.kubernetes.io/use-regex: "true"
spec:
  rules:
  - host: test.com
    http:
      paths:
      - path: /foo/.*
        backend:
          serviceName: test
          servicePort: 80

The preceding ingress definition would translate to the following location block within the NGINX configuration for the test.com server:

location ~* "^/foo/.*" {
  ...
}

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.

Please read the warning before using regular expressions in your ingress definitions.

Example

Let the following two ingress definitions be created:

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress-1
spec:
  rules:
  - host: test.com
    http:
      paths:
      - path: /foo/bar
        backend:
          serviceName: service1
          servicePort: 80
      - path: /foo/bar/
        backend:
          serviceName: service2
          servicePort: 80

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress-2
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /$1
spec:
  rules:
  - host: test.com
    http:
      paths:
      - path: /foo/bar/(.+)
        backend:
          serviceName: service3
          servicePort: 80

The ingress controller would define the following location blocks, in order of descending length, within the NGINX template for the test.com server:

location ~* ^/foo/bar/.+ {
  ...
}

location ~* "^/foo/bar/" {
  ...
}

location ~* "^/foo/bar" {
  ...
}

The following request URI's would match the corresponding location blocks:

• test.com/foo/bar/1 matches ~* ^/foo/bar/.+ and will go to service 3.
• test.com/foo/bar/ matches ~* ^/foo/bar/ and will go to service 2.
• test.com/foo/bar matches ~* ^/foo/bar and will go to service 1.

IMPORTANT NOTES:

• If the use-regex OR rewrite-target annotation is used on any Ingress for a given host, then the case insensitive regular expression location modifier will be enforced on ALL paths for a given host regardless of what Ingress they are defined on.

Warning

The following example describes a case that may inflict unwanted path matching behaviour.

This case is expected and a result of NGINX's a first match policy for paths that use the regular expression location modifier. For more information about how a path is chosen, please read the following article: "Understanding Nginx Server and Location Block Selection Algorithms".

Example

Let the following ingress be defined:

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: test-ingress-3
  annotations:
    nginx.ingress.kubernetes.io/use-regex: "true"
spec:
  rules:
  - host: test.com
    http:
      paths:
      - path: /foo/bar/bar
        backend:
          serviceName: test
          servicePort: 80
      - path: /foo/bar/[A-Z0-9]{3}
        backend:
          serviceName: test
          servicePort: 80

The ingress controller would define the following location blocks (in this order) within the NGINX template for the test.com server:

location ~* "^/foo/bar/[A-Z0-9]{3}" {
  ...
}

location ~* "^/foo/bar/bar" {
  ...
}

A request to test.com/foo/bar/bar would match the ^/foo/[A-Z0-9]{3} location block instead of the longest EXACT matching path.