upload request-body to other service

upload_boby.lua

-- https://github.com/diegonehab/luasocket
local HTTP  = require("socket.http")
local LTN12 = require("ltn12")

-- source for ngx.req.socket()
function source_tcpsock(handle, bytes)
  bytes = tonumber(bytes)
  if handle then
      return function()
          if bytes <= 0 then
            return nil
          end
          local rsize = 2048
          if bytes < rsize then
            rsize = bytes
          end
          local chunk, err, partial = handle:receive(rsize)
          if err then
            ngx.log(ngx.ERR, "receive failed")
            ngx.exit(500)
          end
          if not chunk then
            chunk = partial
          end
          if chunk then
            bytes = bytes - #chunk
          end
          return chunk
      end
  else
    return LTN12.source.error('handle is nil')
  end
end

-- upload uri
local post_uri = 'http://localhost:9292/teapot'

local headers = ngx.req.get_headers()
local reqtype = headers['content-type'] or 'application/json'
local reqsize = headers['content-length'] or '0'

local resbody = {}
local result, rescode, resheaders, resstatus = HTTP.request {
  method = 'POST',
  url = post_uri,
  source = source_tcpsock(ngx.req.socket(), reqsize),
  headers = {
    ["Content-Type"] = reqtype,
    ["Content-Length"] = reqsize
  },
  sink = LTN12.sink.table(resbody)
}

ngx.status = rescode
ngx.header.content_type = resheaders['content-type']
ngx.say(table.concat(resbody))