PowerDNS - DNSQuestion is always nil - lua

I have setup a PowerDNS (4.0.4-1+deb9u4) upon Debian 9 with a MySQL backend successfully and the system was resolving hosts correctly. I am attempting to add scripting to the recursor and have used the examples, Lua script examples. I have pointed the pdns-resolver's conf correctly at my lua script, and I see my log statements print correctly, but I am consistently receiving an error regarding the DNSQuestion instance being empty for all of the example lua functions.
For example:
function preresolve(dq)
pdnslog("Got question for "..dq.qname:toString().." from "..dq.remoteaddr:toString().." to "..dq.localaddr:toString())
return true;
end
Results in :
STL error (a.root-servers.net/A from 127.0.0.1): Trying to cast a lua variable from "nil" to "b" (meaning the DNSQuestion instance is null).
Clearly the lua script is running, but for some reason, all the dq instances are empty.
Is there anything that I may have misunderstood or am missing that would cause the parameter to be nil?

Have your function return true or false so it will not return nil by default.

Related

How can I fix this lua runtime error in pico-8?

I'm following your roguelike tutorial and have encountered a problem I do not know how to solve. This is my first-time coding with Lua
If r.nospawn then return 0
--Attempt to index local "R" (a nil value)
I asked the PICO-8 discord server, they tried to help me, but I still don't fully understand, and I did not want to pester them further with the issue. The name of my file on PICO-8 is called Rogue - if that has anything to do with the issue.
Here's a picture of the error, the discord comment I received, and a link to the full list of code on GitHub.
Error in PICO-8
Discord Comment
Github Code
I think you are missing a simple failure case. i.e. what happens when all the entries in rpot have been removed. Then local r=getrnd(rpot) should return null. That might be an error in it's own right i.e. there should always be something to allocate from there.
However getrnd will fail.
function getrnd(arr)
return arr[1+flr(rnd(#arr))]
end
In the case when arr is empty you will try and return element 1, which will be out of bounds. I don't know lua but it might return null for you which leads to the next problem. But that has a simple fix:
repeat
local r=getrnd(rpot)
if r
placed+=infestroom(r)
del(rpot,r)
end
until #rpot==0 or placed>maxmons[floor]

Error trying to configure esx_addonaccount

I am trying to make a fivem server and have been able to configure esx_addonaccount once before, but now that I have needed to restart my project it is not seeming to work. My database is considered fine, and I am running a completely vanilla install minus the esx framework plugins and esx_addonaccount, which is the problem. This occurs when I load into the server anytime.
Error running system event handling function for resource esx_addonaccount: citizen:/scripting/lua/scheduler.lua:41: Failed to execute thread: #esx_addonaccount/server/main.lua:87: attempt to index a nil value (local 'xPlayer')
stack traceback:
#esx_addonaccount/server/main.lua:87: in upvalue 'handler'
citizen:/scripting/lua/scheduler.lua:219: in function <citizen:/scripting/lua/scheduler.lua:218>
stack traceback:
[C]: in function 'error'
citizen:/scripting/lua/scheduler.lua:41: in field 'CreateThreadNow'
citizen:/scripting/lua/scheduler.lua:218: in function <citizen:/scripting/lua/scheduler.lua:182>
Please help!!
#esx_addonaccount/server/main.lua:87: attempt to index a nil value (local 'xPlayer')
Above is a line from your error. It basically says that in resource esx_addonaccount, in folder ./server/, in file main.lua, in line 87 you are trying to access xPlayer variable, but in this specific case it equals nil. This means that either you have not initialized ESX correctly or somehow xPlayer is not existing - eg. player with given ID doesn't exist.
The best bet would be to check the whole 'path' of this variable - where is it created, initialized and populated with data.
ESX resources should work out of the box, so if it doesn't, then try to follow the installation instructions in their README files or on github and see if you did everything to correctly install them on your server.

Got the error when use LUA script to query a list

when I use Lua script to query a list, I got the correctly result if the list is not empty. But got error if the list is empty.
Blow is my script:
const char * sLuaQueryServers = "local key_list = redis.call('KEYS',
KEYS[1]); return(redis.call('MGET', unpack(key_list)))";
I passed the "serverlist:*" as the key, it's successfully returned the server in list.
But if there no server in redis, I got below error:
ERR Error running script (call to
f_88620231033e13635dc3181f2947a740f91012dc): #user_script:1: #user_script:
1: Wrong number of args calling Redis command From Lua script
"
Please help.
To your question, add a check that the list isn't empty before calling MGET, e.g.:
local key_list = redis.call('KEYS', KEYS[1])
if #key_list > 0 then
return(redis.call('MGET', unpack(key_list)))
else
return nil
end
Note #1: no need for semicolons in Lua
Note #2: Using KEYS isn't recommended for anything, except debugging
Note #3: You're using the KEYS table to pass an argument, but since your script is running KEYS (the command) that's really a moot point

"attempt to call global 'tonumber' (a nil value)" in Lua, embedded (in VLC)

I use VLC media player 1.1.9 on Ubuntu 11.04. I'm trying to experiment with lua extensions for VLC; so I've added the file test.lua in ~/.local/share/vlc/lua/extensions/, which has only these two lines:
fps="25.000"
frame_duration=1/tonumber(fps)
When I run vlc with verbose output for debugging, I get (edited to split on multiple lines:):
$ vlc --verbose 2
...
[0xa213874] lua generic warning: Error loading script
~/.local/share/vlc/lua/extensions/test.lua:
.../.local/share/vlc/lua/extensions/test.lua:2:
attempt to call global 'tonumber' (a nil value)
...
Now, as far as I know, tonumber as function is part of Lua5.1 proper (Lua 5.1 Reference Manual: tonumber) - and on my system:
$ locate --regex 'lua.*so.*' | head -4
/usr/lib/libipelua.so.7.0.10
/usr/lib/liblua5.1.so
/usr/lib/liblua5.1.so.0
/usr/lib/liblua5.1.so.0.0.0
... apparently I do have Lua 5.1 installed.
So, why do I get an error on using tonumber here - and how can I use this (and other) standard functions in a VLC lua extension properly?
Documentation is sparse for VLC Lua extensions to say the least but I did find an example in the github vlc repository here: https://github.com/videolan/vlc/blob/master/share/lua/extensions/VLSub.lua
Judging from that example it appears you need to supply some basic event functions for your addon for VLC to call into when certain events happen. Some of the obvious callback handlers I've noticed:
descriptor, this should return a table that contains fields describing your addon.
activate, this seems to get called when you activate it from view menubar.
deactivate, called when you deactivate the addon from view menubar.
plus a couple of other functions like close and input_change which you can guess what they're for.
From my brief testing done on VLC 2.0.8 under Win7 it appears VLC loads the lua extension using an empty sandbox environment. This is likely the reason you're getting nil for tonumber and I'm betting none of the other standard lua functions are accessible either when you try to perform computation at this global scope.
However, if I move that code into one of the event handling functions then all those standard functions are accessible again. For example:
function descriptor()
return
{
title = "Test Ext";
version = "0.1";
author = "";
shortdesc = "Testing Lua Extension";
capabilities = {};
description = "VLC Hello Test Addon";
}
end
function activate()
print "test activating"
local fps = tonumber "25.000"
local frame_duration = 1 / fps
print(frame_duration)
return true
end
-- ...
That prints out what you would expect in the console debug log. Now the documentation (what little there is) doesn't mention any of this but what's probably happening here is VLC is injecting the standard lua functions and vlc api table into the sandboxed environment when any of these event handlers get called. But during the extension loading phase, it is done in an empty sandbox environment which explains why all those lua function calls end up being nil when you try to use it at the outter most scope.
I recommend cloning the VLC source tree from github and then performing a grep on the C source that's embedding lua to see what VLC is really doing behind the scenes. Most of the relevant code will likely be here: https://github.com/videolan/vlc/tree/master/modules/lua
Probably some extension script installed in your system overwrites the function and the Lua interpreter instance is shared between all extension scripts, so you end up not being able to call the function if that script is called before yours.
As a quick workaround, Lua being dynamically typed, you can still do things like:
1 / "25.000"
and the string will be coerced to a number.
Alternatively, you can define a tonumber equivalent like:
string_to_num = function(s) return s + 0 end
This again relies on dynamic typing.

Lua error for WoW addon (Tukui)

I don't have a lot of coding experience, did some C a few years ago, so that helps, but Lua handles things a bit differently, so I can't keep track.
I sometimes (not always) get this error when a friend or guildy logs into the game:
Date: 2013-06-14 16:57:57
ID: -1
Error occured in: Global
Count: 4
Message: ..\AddOns\Tukui\scripts\chat.lua line 335:
attempt to concatenate upvalue 'classColor' (a nil value)
Debug:
[C]: ?
Tukui\scripts\chat.lua:335: AddMessage()
..\FrameXML\ChatFrame.lua:2755: ChatFrame_MessageEventHandler()
..\FrameXML\ChatFrame.lua:2491: ChatFrame_OnEvent()
...s\WIM\Libs\LibChatHandler-1.0\LibChatHandler-1.0.lua:281:
...s\WIM\Libs\LibChatHandler-1.0\LibChatHandler-1.0.lua:252
...s\WIM\Libs\LibChatHandler-1.0\LibChatHandler-1.0.lua:308:
...s\WIM\Libs\LibChatHandler-1.0\LibChatHandler-1.0.lua:296
I have to do a reload of the ui after this happens to be able to see chat text again for that person.
Line 335 in that .lua file is this:
text = replace(text, "^|Hplayer:(.+)|h%[(.+)%]|h", "|Hplayer:%1|h|cff"..classColor.."%2|r|h")
Now I've learned that the .. indicates the concatenate function, but that isn't really helping me.
I don't know if this is enough information, but if you need it I can post the whole local function or whatever else is required.
If it makes any difference, I'm running the 3.3.5a WoW client.
You are probably using a global that gets defined from some other addon in a now deterministic way
While the (classColor or "") will get you rid of the error, you should try and find why that variable (classColor) is sometimes defined and sometimes not. Maybe it happens only for certain classes?
A simple hack would be to just replace
..classColor..
with
..(classColor or "")..
where it will select a blank string when classColor has no value assigned to it.

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