Paths using regex containing the $ character need to be escaped when setting $location_path in the nginx template

[bshelton229]

Is this a request for help? (If yes, you should use our troubleshooting guide and community support channels, see https://kubernetes.io/docs/tasks/debug-application-cluster/troubleshooting/.):

What keywords did you search in NGINX Ingress controller issues before filing this one? (If you have found any duplicates, you should instead reply there.):

---

Is this a BUG REPORT or FEATURE REQUEST? (choose one):

NGINX Ingress controller version: unreleased

Kubernetes version (use kubectl version): 1.10

Environment:

• Cloud provider or hardware configuration: AWS
• OS (e.g. from /etc/os-release): Amazon Linux 2
• Kernel (e.g. uname -a): 4.14.62-70.117.amzn2.x86_64
• Install tools: AWS EKS
• Others:

What happened:

The emerging support for regex paths is really awesome! Thanks @zrdaley . We've been using a custom template in testing to achieve this so far and are really happy to know we'll be able to avoid that. We have a couple paths that contain $ in the regex pattern. For example, we have one called "homepage" which only receives traffic from /, in which case we're using /$ to end up with location ~* "^/$" {.....

When there is a $ character in path it causes nginx errors from the following template declaration - set $location_path "{{ $location.Path }}"; because nginx variables can't contain $. I've yet to be able to find a way to escape an actual $ character in an nginx variable. I'll open a PR with what we're currently doing in testing to get this working in order to get a conversation started.

What you expected to happen:

It would be nice to support $ in regex enabled paths and have the $location_path nginx variable contain something escaped in some way.

How to reproduce it (as minimally and precisely as possible):

Fulfilling an ingress resource with a path containing a $ should be enough to reproduce the issue.

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: hello-world-ingress
  labels:
    app: hello-world-ingress
  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/use-regex: "true"
spec:
  rules:
    - host: hello-world.example.com
      http:
        paths:
          - path: /hello$
            backend:
              serviceName: my-service-hello-only
              servicePort: http
          - path: /
            backend:
              serviceName: my-service
              servicePort: http

This should fail to reload or boot nginx with an error like:

2018/10/05 18:00:59 [emerg] 95#95: invalid variable name in /tmp/nginx-cfg577284661:398

Anything else we need to know:

[zrdaley]

Which controller version are you using? This issue should have been fixed here: #3182.

Version 0.20.0 will have this update.

[bshelton229]

I've been building master. I'm currently seeing this from b46523a. Before the regex work landed in master we were using a custom template that did something similar to what's now done in the controller and ran into this same issue there. Given we were using a custom template we just removed that set as we didn't need the variable.