response.set_raw_body support

[mpromny]

HI, I'd like to ask whether there is a chance that the response.set_raw_body() functionality introduced in Kong 2.8.0 will be added soon.

Kind Regards, Mateusz

[fffonion]

@mpromny All Kong PDK functions supported by Kong are automatically supported in python-pdk; there might be some missing docs (and .pyi interfaces) but you can use them.

[mpromny]

@fffonion Again, thank you for your immediate help. It works as you said.

[mpromny]

Hi @fffonion ,

Would you please help me once more? Unfortunately, I am forced to reopen this issue and ask for some guidelines or clarification on what I am doing wrong.

Requirements:

• modify body of requests and responses based on header

Current Env:

• Kong: 2.8.1
• kong-python-pdk: 0.3
• K8s with Istio (http2) - extra condition, currently disabled to force HTTP 1.1

Current Status:

• Modify Request body - it is working (Access Phase)
• Modify Response body - I cannot activate body_filter phase

Code:

    def rewrite(self, kong: Kong):
        kong.service.request.enable_buffering()

    def access (self, kong: Kong):
        try:
            if true:
                kong.service.request.enable_buffering()
                self.transform_request_body(kong, kong.request.get_body())
        except Exception as err:
            kong.log.err(f"TRANSFORMATION - error: {err}")
            return self.error_response(kong, "Transformation issue")

    def body_filter(self, kong: Kong):
        body0 = kong.response.get_raw_body()
        body1 = kong.service.response.get_body()
        body2 = kong.service.response.get_raw_body()
        kong.response.set_raw_body("{}")
        kong.log.debug(f"PHASE body_filter")
        kong.response.exit(404, "body_filter phase")

Issue/Questions:

1) I cannot activate body_filter phase. I would ask for any tips on what I might be doing wrong. Based on the documentation:

Plugin needs to call kong.service.request.enable_buffering() on `rewrite` or `access` phase prior calling this function.

Clarification:

• above posted code has been tested on components without Istio, with forced http 1.1 protocol.

2) I found information that kong.service.request.enable_buffering() works only for http/1.1. Therefore I assume that get/set response body will not work with istio/envoy which uses http2. Would you please confirm that?

Kind regards, Mateusz

[fffonion]

Hi @mpromny there're two factors in play here:

• First one is external plugins doesn't support body_filter yet; to get a response body from external plugin, you will need to use the response phase.
• Response phase doesn't work with http/2 requests, same limitation as you found. So yes the end result is you can't get the http/2 body in an external plugin for now. The limitation is not exist for non-http/2 request, or Lua plugins.

[mpromny]

Hi @fffonion,

1) Unfortunately, I was not able to get the response body in response phase

• response phase

I tested the below pasted code:

    def response(self, kong: Kong):
        body = kong.service.response.get_raw_body()

        kong.log.err(f" { body[0]} ")
        kong.response.exit(404, "body_filter phase")

and was able only to get/see request body instead of response body:

Request Body:
{"mat": "test"}

2) Lua plugins

May I ask you to confirm, if I understand correctly:

We have to use "lua plugins" if we want to:

• modify response and requests body
• plugins in lua are not constrained by the http version. In other words, in lua we will be able to process (get/set features) response bodies freely, regardless of the http protocol version.

3) I would ask for some guidelines/advice on how you think it would be best to implement response/request body processing in Kong. Do you think that there is any chance that access to response body will be easier in the near future?