nginx-lua: upload request-body to other service without LuaSocket

upload_body.lua

local function header_join_with_crlf(header)
  local str = "", k, v
  for k,v in pairs(header) do
    str = str .. v .. "\r\n"
  end
  return str
end

-- @return client, err
local function connect(ngxctx, host, port, path)
  local ok, err
  local obj = {}
  obj.clientsock, err = ngxctx.req.socket()
  if err then
    return nil, 'failed to get sock - ' .. err
  end
  obj.serversock = ngxctx.socket.tcp()
  ok, err = obj.serversock:connect(host, port)
  if not ok then
    return nil, 'failed to connect: ' .. host .. ':' .. port .. ' - ' .. err
  end
  obj.path = path
  obj.send_header = function(self, m)
                      local method  = m or ngxctx.req.get_method()
                      local headers = ngxctx.req.get_headers()
                      local reqtype = headers['content-type'] or 'application/json'
                      local reqsize = headers['content-length'] or '0'
                      local header = {method.." "..path.." HTTP/1.0", "Content-Type: "..reqtype, "Content-Length: "..reqsize, ""}
                      local bytes, err = self.serversock:send(header_join_with_crlf(header))
                      if err then
                        self.err = 'failed to send header - ' .. err
                        return nil
                      end
                      self.reqsize = reqsize
                      return true
                    end
  obj.send_body =   function(self)
                      local size = tonumber(self.reqsize)
                      while size>0 do
                        local rsize = 2048
                        if size<rsize then rsize=size end
                        local data, err, partial = self.clientsock:receive(rsize)
                        if err then
                          self.err = 'failed to receive request body - ' .. err
                          return nil
                        end
                        if not chunk then chunk = partial end
                        local bytes, err = self.serversock:send(data)
                        if err then
                          self.err = 'failed to send request body - ' .. err
                          return nil
                        end
                        size = size - rsize
                      end
                      return true
                    end
  obj.recv_header = function(self)
                      self.content_length = nil
                      while true do
                        local data, err, partial = self.serversock:receive()
                        if err then
                          self.err = 'failed to receive response - ' .. err
                          return nil
                        end
                        if not data then data = partial end
                        local m, err = ngxctx.re.match(data, "HTTP/1.[01] ([0-9]+)", "i")
                        if m then ngxctx.status = tonumber(m[1]) end
                        m, err = ngxctx.re.match(data, "content-type: (.+)", "i")
                        if m then ngxctx.header.content_type = m[1] end
                        m, err = ngxctx.re.match(data, "content-length: ([0-9]+)", "i")
                        if m then self.content_length = tonumber(m[1]) end
                        if data=="" then break end
                      end
                      return true
                    end
  obj.recv_body =   function(self)
                      if self.content_length then
                        local data, err, partial = self.serversock:receive(self.content_length)
                        if err then
                          self.err = 'failed to receive response - ' .. err
                          return nil
                        end
                        if not data then data = partial end
                        ngxctx.header.content_length = #data
                        ngxctx.say(data)
                      end
                      return true
                    end
  obj.request = function(self, m)
                  local ok = self:send_header(m) and self:send_body() and self:recv_header() and self:recv_body()
                  self.serversock:close()
                  return ok
                end
  return obj
end

-- upload
local client, err = connect(ngx, '127.0.0.1', 80, '/teapot')
if err then
  ngx.log(ngx.ERR, err)
  return ngx.exit(500)
end
if not client:request('PUT') then
  ngx.log(ngx.ERR, client.err)
  return ngx.exit(500)
end