in body_filter_by_lua get all resopnse send Third party services

openResty 1.1.1c
Here is my code snippet
nginx.conf
server {
listen 7788;

	location /kk {
		access_by_lu_file  access.lua;
                     header_filter_by_lua_file   header.lua;
                     body_filter_by_lua_file   header.lua;
                     proxy_pass http://127.0.0.1/uri;
	}
}

body.lua

local socket = require"resty.handler"
if ngx.arg[1] ~= "" then
socket:body_filter()
socket:sendBody()
end

if ngx.ctx.encrypt then
local chunk, eof = ngx.arg[1], ngx.arg[2]
local buffered = ngx.ctx.buffered
if not buffered then
buffered = {}
end

if chunk ~= "" then
	buffered[#buffered + 1] = chunk
	ngx.arg[1] = nil
end

if eof then
	local whole = table.concat(buffered)
	
	ngx.arg[1] = ngx.encode_base64(whole)
end

end

handler.lua

     local M = {_VERSION = '0.0.1'}

    function _M.body_filter()

-- body
local chunk, eof = ngx.arg[1], ngx.arg[2]
local buffered = ngx.ctx.buffered
if not buffered then
	buffered = {}
end

if chunk ~= "" then
	buffered[#buffered + 1] = chunk
	ngx.arg[1] = nil
end

if eof then
	local whole = table.concat(buffered)
	
	ngx.ctx.response_body = whole
end

end

function _M.sendBody()

-- body
--lua tcp send response_body
socket.send(ngx.ctx.response_body)

end
return _M

when ngx.ctx.encrypt == true I can get ngx.ctx.respnse_body and send response

but else ngx.ctx.encrypt == false I can not get ngx.ctx.respnse_body and ngx.ctx.response_body = ""

Start with the nginx.conf configuration and compare the body_filter_by_lua_file flow in body.lua with handler.lua. Reproduce the encrypt=false case and trace when ngx.ctx.response_body is assigned and read. Done means the cause of the empty value is identified and the response body is reliably available in the intended path.