Regular expressions with "?!" are not supported in VirtualServer

[LuciferInLove]

Describe the bug Regular expressions that contains "?!" not supported in path or routes and subroutes in VirtualServer and VirtualServerRoute resources.

To Reproduce

1. Deploy yamls:

apiVersion: k8s.nginx.org/v1
kind: VirtualServer
metadata:
  name: cafe
  namespace: default
spec:
  host: cafe.example.com
  upstreams:
  - name: tea
    service: tea-svc
    port: 80
  routes:
  - path: /tea
    action:
      pass: tea
  - path: /coffee
    route: default/coffee

apiVersion: k8s.nginx.org/v1
kind: VirtualServerRoute
metadata:
  name: coffee
  namespace: default
spec:
  host: cafe.example.com
  upstreams:
  - name: latte
    service: latte-svc
    port: 80
  - name: espresso
    service: espresso-svc
    port: 80
  subroutes:
  - path: ~ ^/coffee/latte$ # it's works
    action:
      pass: latte
  - path: ~ ^/coffee/(?!.*\/latte)(?!.*\/americano)(.*) # it isn't working
    action:
      pass: espresso

2. View logs on ingress-controller pod
3. See error:

I1223 08:46:01.744934       1 controller.go:1369] Skipping invalid VirtualServerRoute default/coffee: spec.subroutes[1].path: Invalid value: "~ ^/coffee/(?!.*\/latte)(?!.*\/americano)(.*)": must be a valid regular expression: error parsing regexp: invalid or unsupported Perl syntax: `(?!`

Expected behavior All regular expressions that work in bare nginx must work in path.

Your environment

• Version of the Ingress Controller - release version or a specific commit 1.6.0
• Version of Kubernetes 1.15.3
• Kubernetes platform (e.g. Mini-kube or GCP) bare kubernetes
• Using NGINX or NGINX Plus NGINX

Aha! Link: https://nginx.aha.io/features/IC-109

[pleshakov]

Hi @LuciferInLove thanks for reporting!

The supported regex syntax is currently limited by regular expressions supported in golang https://github.com/google/re2/wiki/Syntax

We might overcome this limitation in the future.

Are there any workaround regular expressions that you could use that can cover your case?

[LuciferInLove]

Are there any workaround regular expressions that you could use that can cover your case?

Unfortunately, no, but now I'm using bare nginx deployed in k8s with own customizations.

[pleshakov]

Ok. We'll keep the issue open to track this limitation.

[github-actions[bot]]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[LuciferInLove]

Just a comment to leave this issue open.

[github-actions[bot]]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[LuciferInLove]

Just a comment to leave this issue open.

[github-actions[bot]]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[LuciferInLove]

Just a comment to leave this issue open.

[jnewfield]

I came across this issue recently. Seems kic should implement regex libraries that more closely matches that which NGINX uses, such as go pcre2.

[artbegolli]

any updates here? or any suggestions for work arounds?

[danielnginx]

We could also leverage the following libraries:

https://pkg.go.dev/github.com/s-kozlov/goback/regexp/syntax

https://pkg.go.dev/github.com/dlclark/regexp2#section-readme

[jjngx]

test log:

I1003 13:52:25.597291       1 event.go:298] Event(v1.ObjectReference{Kind:"VirtualServer", Namespace:"default", Name:"cafe", UID:"eb5fa829-4f39-4cd1-973a-78282d2d76d2", APIVersion:"k8s.nginx.org/v1", ResourceVersion:"277941", FieldPath:""}): type: 'Warning' reason: 'AddedOrUpdatedWithWarning' Configuration for default/cafe was added or updated with warning(s): VirtualServerRoute default/coffee doesn't exist or invalid
I1003 13:52:46.350360       1 event.go:298] Event(v1.ObjectReference{Kind:"VirtualServerRoute", Namespace:"default", Name:"coffee", UID:"d9c0f987-02e7-4554-8a8e-6ac7088afa54", APIVersion:"k8s.nginx.org/v1", ResourceVersion:"277976", FieldPath:""}): type: 'Warning' reason: 'Rejected' VirtualServerRoute default/coffee was rejected with error: spec.subroutes[1].path: Invalid value: "~ ^/coffee/(?!.*\\/latte)(?!.*\\/americano)(.*)": must be a valid regular expression: error parsing regexp: invalid or unsupported Perl syntax: `(?!`

[jjngx]

Employing regexp2 package that uses Perl5 / .NET compatible regex implementation engine solves the path validation problem.