RequestRedirect filter on HTTPRoute cannot preserve path in request

[randmonkey]

Is there an existing issue for this?

• I have searched the existing issues

Does this enhancement require public documentation?

• I have added an Acceptance Criteria item for adding and/or adjusting public documentation (if applicable)

Problem Statement

From FTI-6305.
Because the RequestRedirect filter is implemented by request-termination and response-transformer plugin. This cannot include variable part in the response head. So the redirect path in the response body is fixed and cannot preserve path in the request.

Proposed Solution

• Use some other method to generate redirect response that can send variable response according to the request
  • For example: run a standalone server to send responses

Additional information

No response

Acceptance Criteria

• Redirect path in the response header can be preserved if no path is given
• ReplacePrefixMatch is also supported

[mheap]

Can this be implemented with a pre-function plugin?

kong.response.exit(301, 'redirecting', {['Location'] = 'https://other.example.com/' .. kong.request.get_path_with_query()})

[randmonkey]

@mheap has submitted a PR for adding a redirect plugin: Kong/kong#13900
Using the plugin (only for Kong 3.9, or other version that contains the plugin) should resolve this.
If Kong does not support this plugin, we should either:

• Do not support it and report a translation error
• Implement by pre-function plugin
  @mheap Which one do you think is the better resolution?

[mheap]

I think we should leave the existing implementation pre 3.9, and use the new plugin in 3.9+.

pre-function is used enough that I would not want to prevent users using it if adding redirects

[randmonkey]

Now Kong/kong#13900 is merged and we can use the redirect plugin if Kong version is above or equal to 3.9. However, the plugin seems still cannot satisfy the replacePrefixMatch. @mheap do we have plan to support it?

[lahabana]

Let's just move support for ReplacePrefixMatch to a future release and do just redirect in 3.4 to be able to close the FTI.