Standardize requests to lowercase for proxy-cache to work?

[tobiasehlert]

Hello,

My issue I got is that people are sending requests to my API with most of the times lowercase letter, but some also send first letter as capital or randomized, since the proxy-cache handles the requests as unique.

On this way, they can get around my cache, which is a bit annoying actually.

Example paths:

• /api/greeting/tobias
• /api/greeting/Tobias
• /api/greeting/tObIaS

Is there some smart thing that can make proxy-cache handle those requests as the same request?

Maybe place an nginx in front of the Kong gateway to rewrite the path with lua?
Like this example: https://www.rewriteguide.com/nginx-enforce-lower-case-urls/

Maybe that it passes it to the backend but there I return a redirect to the lowercase url if I detect some uppercase?

Kind regards,
Tobias

[tobiasehlert]

I guess a way forward is to add the Pre Function (https://docs.konghq.com/hub/kong-inc/serverless-functions/) plugin in this case.. I'll test with it.

[tobiasehlert]

Here is how I solved it.. added following lua in my pre-function on the global level in the access field:

kong.service.request.set_path(string.lower(kong.request.get_path())) 

[flrgh]

@tobiasehlert if you want to simply normalize/rewrite the uri in-place, this is possible by using the request-transformer plugin with its advanced template feature:

https://docs.konghq.com/hub/kong-inc/request-transformer/#advanced-templates

The uri/path is not injected into the template environment by default, so we'll need to use a route with a uri capture to make it available:

---
name: my-route
paths:
  # this makes `uri_captures.person` accessible to our request-transformer template
  - "/api/greeting/(?<person>.+)"
service: ...
plugins:
  - name: request-transformer
    config:
      replace:
        # here we use the Lua `string.lower()` metamethod to normalize our API path to lowercase:
        uri: "/api/greeting/$(uri_captures.person:lower())"

The other strategy might be to return a 301 redirect to the proper, normalized uri, but that would require using the pre-function plugin with a little more effort.