how to get response body

[eddie04]

I hope to use kong.service.response.get_raw_body() to get the response body in the log phase.
Before that, I have used kong.service.request.enable_buffering() in the access phase.
Then it gave me an exception as follows:

[error] 29#0: *10290 failed to run log_by_lua*: ...are/lua/5.1/kong/plugins/log-authorize/handler.lua:396: service body is only available with buffered proxying (see: kong.service.request.enable_buffering function)
stack traceback:
        [C]: in function 'error'
        /usr/local/share/lua/5.1/kong/pdk/service/response.lua:283: in function 'get_raw_body'
        ...are/lua/5.1/kong/plugins/log-authorize/handler.lua:396: in function <...are/lua/5.1/kong/plugins/log-authorize/handler.lua:383>
        /usr/local/share/lua/5.1/kong/init.lua:265: in function 'execute_plugins_iterator'
        /usr/local/share/lua/5.1/kong/init.lua:1300: in function 'log'
        log_by_lua(nginx-kong.conf:100):2: in main chunk while logging request

[bungle]

@eddie04, what version of Kong are you using? I am assuming 2.4.0?

[bungle]

@eddie04 are you sure your plugin executed that kong.service.request:enable_buffering() line? Perhaps there was an error before or after executing that line?

[bungle]

@eddie04, can you give us any step by step intsructions that how do you get that error?

I wrote this plugin, and it seemed to work alright (do you use custom nginx templates or anything like that?):

local BuggyHandler = {}


BuggyHandler.PRIORITY = 500
BuggyHandler.VERSION = "1.0.0"


function BuggyHandler:access(conf)
  ngx.log(ngx.ERR, "before access")
  kong.service.request:enable_buffering()
  ngx.log(ngx.ERR, "after access")
end


function BuggyHandler:log(conf)
  ngx.log(ngx.ERR, "before log")
  local body = kong.service.response.get_raw_body()
  ngx.log(ngx.ERR, tostring(body))
  ngx.log(ngx.ERR, "after log")
end


return BuggyHandler

[eddie04]

Yes, the version of Kong is 2.4.0 (OSS), and i used follow codes:

function plugin:access(plugin_conf) 
    kong.service.request.enable_buffering()
    ...
    ...
    ...
end

function plugin:log(plugin_conf)
   if kong.response.get_status() == 500 then
        local json = cjson.new() -- require "cjson"
        kong.log.debug(json.encode(kong.service.response.get_raw_body())) -- error line
   end
end

Then i got an error above, actually i used this template: https://github.com/Kong/kong-plugin.

[bungle]

@eddie04, how did you install Kong? What is the listing of kong version -vv?

[bungle]

@eddie04, also did you know about the limitation that it can be enabled with http 1.1 only, e.g. clients making requests with http 2 will fail? It is an unfortunate limitation with OpenResty, perhaps we should not error on it.

[eddie04]

I reinstalled my custom plugin，it's ok now，there is no problem.

function plugin:access(plugin_conf)

  kong.service.request.enable_buffering()
  
end

function plugin:log(plugin_conf)
  local event_state="failed"
  local fail_reason= ""

  if kong.response.get_status() >= 200 and kong.response.get_status() < 300 then
    event_state = "success"
  else
    local res_body_string = tostring(kong.service.response.get_raw_body())
    kong.log.debug("response body:",res_body_string)
    fail_reason = res_body_string
  end
  
end

BTW I installed Kong in Docker container, and http version is 1.1.

request: "POST /api/whitelist/query HTTP/1.1"

Thanks a lot, @bungle !

[eddie04]

The error happened again when rewrite response with 403 status code in access phase.

return kong.response.exit(403, err_resp, { ["Content-Type"] = "application/json" })

service body is only available with buffered proxying (see: kong.service.request.enable_buffering function)
stack traceback:
        [C]: in function 'error'
        /usr/local/share/lua/5.1/kong/pdk/service/response.lua:283: in function 'get_raw_body'
        ...are/lua/5.1/kong/plugins/log-authorize/handler.lua:399: in function <...are/lua/5.1/kong/plugins/log-authorize/handler.lua:384>
        /usr/local/share/lua/5.1/kong/init.lua:265: in function 'execute_plugins_iterator'
        /usr/local/share/lua/5.1/kong/init.lua:1300: in function 'log'
        log_by_lua(nginx-kong.conf:100):2: in main chunk while logging request, client: xxx, server: kong, request: "POST /api/whitelist/query HTTP/1.1", host: "xxx:8000"
xxx - dsmuser [30/Apr/2021:05:41:14 +0000] "POST /api/whitelist/query HTTP/1.1" 403 38 "-" "PostmanRuntime/7.26.8"

[gszr]

@eddie04, Can you share the code for the plugin, with the change you mentioned? The code as you shared above works fine on my end.