Lua错误摘要

coroutine 0:
	/usr/local/openresty/lualib/resty/mysql.lua: in function '_send_packet'
	/usr/local/openresty/lualib/resty/mysql.lua:781: in function 'close'
	/root/lua/ad_readdata.lua:5: in function </root/lua/ad_readdata.lua:1>, client: 192.168.137.1, server: localhost, request: "GET /lua_mysql HTTP/1.1", host: "192.168.137.128"
2020/06/22 06:05:04 [error] 53753#53753: *460 lua entry thread aborted: runtime error: /usr/local/openresty/lualib/resty/mysql.lua:236: attempt to perform arithmetic on field 'packet_no' (a nil value)
stack traceback:

 lua连接数据库时报以上错误，下面是执行的脚本摘录

local cjson = require("cjson")
local mysql = require("resty.mysql")


local db = mysql:new()
db:set_timeout(10000)  
local props = {  
         ***************  
}

local res = db:connect(props)  
local select_sql = "*************"  
res = db:query(select_sql)  
db:close()  

 解决方案需要注释db:close代码

另外连接数据库或者redis的地址最好用IP地址，不要用域名。因为有几次用域名导致获取的缓存是空的。