Re: Embedding - user inputted scripts design advice

[Sean Conner <sean@...>]

It was thus said that the Great Bruce Wheaton once stated:
> What's the usual way to deal with the user changing their scripts in an
> app with embedded lua scripting? I presume I really have to reset the lua
> state in some way, so any functions that were defined (or variables) that
> they no longer want are removed correctly?
> 
> Is there an accepted way to retain values of the items that they did
> leave, to help with the case of a simple change, like to a calculation?
> 
> And then is it usual to reset and rebind all external class/object
> bindings, or is a 'soft' reset possible?

  It really depends upon the use case.  You can reset the Lua state (or
rather, close it, then re-open and re-initialize a new one), or re-use the
existing Lua state.

  For syslogintr [1] I don't bother with resetting the Lua state at all if
the given script is reloaded.  I do, however, do this (from [2]):

	if blocked == nil then
	  blocked = {}
	  setmetatable(blocked,{ __index = function(t,k) return 0 end })
	  os.execute("iptables --table filter -F INPUT")
	end

to keep from resetting some persistent data [3].  But in general, there are
no hard and fast rules.  

  -spc

[1]	http://www.conman.org/software/syslogintr/
	https://github.com/spc476/syslogintr

[2]	https://github.com/spc476/syslogintr/blob/master/modules/ssh-iptables.lua

[3]	This module of syslogintr tracks failed ssh attempts, and after five
	attempts, will block the offending IP address.  The blocks are
	removed after a few hours to keep the ruleset in iptables from
	ever-increasing.