Environment
Openresty1.15， luajit use openresty branch（2020/01), and the problem still exists when we use the newest version(https://github.com/openresty/luajit2)
Description of the problem
We use two url(only this two continuous url can cause error ) to access our server(http)，server will occur a error with great probability such as "attempt to perform arithmetic on local ‘id’（a boolean value" )
Code analysis
session is a table which define in a lua module（can be considered as a global variable）, and business is a table too. the type of session.business['id'] is number and the value is 0 at the begin of initialization.
session.lua:
function _M.GetBusinessinfo(key)
if key then
return self.business[key]
else
return self.business
end
end
rewrite.lua:
local id = session:GetBusinessInfo('id')
local test = id + 1
Error occurs at "id + 1". we print some information as following, and the type of "id" is boolen and the value is true.
ngx.log(ngx.ERR,"type:",type(id),",value",id)
Then we print information by another mode as following：
for k, v in pairs(session.bussine) do
info = info .. '[' .. tostring(k) .. ']' .. tostring(v)
end
ngx.log(ngx.ERR,info)
We find that the type of "session.business['id']" is number and the value is 0, which is correct.
In summary, looping table is correct, but getting value from table by session.business['id'] is wrong.
Then we packet this two code line to a function in a lua module as following, error does not occur.
session.lua:
function _M:AddSliceId()
local id = self.business['id']
if id then
self.business['id'] = id + 1
end
end
rewrite.lua:
session:AddSliceId()_
Gdb analysis(error has happened)
a. session's memory is as following:
lval (TValue)0x40031477b240
...
key：
string: "business"(len 8 )
value:
table: (TValue)0x4003169120f8
...
Continue to print 0x4003169120f8
lval (TValue*)0x4003169120f8
...
key:
string: "id"(len 2)
value:
number 0
It prove that the table is currect in memory.
b. ltrace
ltrace
Found 51 traces
then loop the result, we can find GetBusinessinfo:
ltrace 31
(GCtrace*) 0x40035009f3d0
machine code size:1524
machine code start addr:0x400008cef020
machine code end addr: 0x40000cef614
@/path/session.lua:323
And part of the code of session.lua is as following:
session.lua:
323:function _M.GetBusinessinfo(key)
324: if key then
325: return self.business[key]
326: else
327: return self.bussine
328: end
329:end
So we can be sure that jit compile mode(not interpreter mode) result in this error.
Then we close the jit as following at the begin of code:
if jit then
jit.off();jit.flush()
end
The error does not occur.
Above is our analysis, who can help me to resolve the problem, thank you.
