How to modify response Body

prkshdalmia · September 4, 2019, 12:29pm

I wanted to modify/edit/replace the response body when there is an Error in the upstream response.

For Example:
When there is a 404 error; I want to edit the response body as “Hey Something is Fishy. Try checking the path”.

jeremyjpj0916 · September 4, 2019, 2:59pm

As far as open source plugins go I believe right now you would need to write a custom plugin checking the HTTP Status from your backend’s and then setting the response body to configured messages(that could be stored in the plugin schema as well) per Status.

I assume this because the response transformer:

Is all based on replacing X with Y, when you want if(Z) replace X with Y, they might accept a new config option like config.only_on_status maybe that if it was set to various HTTP Status numbers that would cause the response body to be replaced.

Cheers,
Jeremy

prkshdalmia · September 5, 2019, 7:01am

Thanks Jeremy,
Yes I constructing a custom Plugin only. But I wanted to know the kong command to modify the response body.
like for changing response header we use kong.response.set_header(). Do we have anything for set_body

jeremyjpj0916 · September 5, 2019, 8:19pm

Yep, that logic starts here in the existing plugin(body_filter phase):

github.com

Kong/kong/blob/master/kong/plugins/response-transformer/handler.lua#L20






local ResponseTransformerHandler = {}




function ResponseTransformerHandler:header_filter(conf)
  header_transformer.transform_headers(conf, kong.response.get_headers())
end




function ResponseTransformerHandler:body_filter(conf)
  if is_body_transform_set(conf) and is_json_body(kong.response.get_header("Content-Type")) then
    local ctx = ngx.ctx
    local chunk, eof = ngx.arg[1], ngx.arg[2]


    ctx.rt_body_chunks = ctx.rt_body_chunks or {}
    ctx.rt_body_chunk_number = ctx.rt_body_chunk_number or 1


    if eof then
      local chunks = concat(ctx.rt_body_chunks)
      local body = body_transformer.transform_json_body(conf, chunks)

Edit- Removed PDK link as I don’t think it works for that case.

prkshdalmia · September 6, 2019, 5:59am

Thankx Jeremy. I think this will do the job.

sivasubramani30 · October 7, 2022, 11:30am

Hi,
Is it worked for you?

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How to modify response Body

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