Config file: global variables vs "config getcher" function

Hi all,

This is a general programming question, not specific to Elixir. I do my fare share of scripting in LUA. Specifically I code IVR on freeswitch / Asterisk. So a common scenario I have is that there is a bunch of configurations parameters that I have to load in memory every time I run a script (e.g. every time a call hits the IVR). I am coding a project now where the number of configuration parameters is quite large (about 200) - please do not focus on the why of this, that is not the aim of the question.

So, what I usually do is to have a config.lua somehere where I define all these parameters as global variables:

__parameter001__ = value01
__parameter001__ = value02
__parameter_N__ = value_N

Not elegant but it does the job. So, I was thinking, would it be more efficient to have a “config getcher” fuction? Something like this :

function  get_parameter(parameter)
   if(parameter == '__parameter001__')then return value01; 
     elseif(parameter == '__parameter002__')then return value02;
     elseif(parameter == '__parameter_N__')then return value_N; 
     else return 'no_value_set';
    end;
end

In my code I would simply call this function everytime I need a parameter value:

my_parameter = get_parameter('__parameter001__');

So, instead of loading a lot of global variables I would be calling a function every time to get the value of a parameter.

My question is: is this something sensible to do? Should I just simply keep loading the parameters in memory?

I know this is not an Elixir question and my example is LUA based but I believe this is language independent discussion. Also, this forum is much more professional than any LUA forum out there (that I know of), so I’d love to know your opinion.

Thank you!

I don’t see why not. Can’t comment on Lua in particular but in Elixir I’d just load these into a Map and then store it and use it like so:

defmodule MyConfig do
  @config_key :my_config

  def load(file_path) do
    # load your configuration parameters into an Elixir map.
    # ...your code here...

    # then, assuming your map with the loaded config is called `cfg`:
    :persistent_term.put(@config_key, cfg)
  end

  def get(param), do: :persistent_term.get(@config_key) |> Map.get(param)
end

That way, you are putting that 200+ keyed map in an in-memory cache that does not get copied when accessed and you have a hyper-fast config map.

(This approach assumes that you’d change that config map rather rarely, by the way.)

1 Like

Thank you @dimitarvp. No need to comment on LUA, it was just to set the example. So, I think what you do with the map is similar to option 1: loading all variables into memory but in a more efficient way (the map) which in turn is accessed by a function. I never change the parameters by the way, they are inmutable…

That absolutely helps me to have a better grasp on how to approach this efficiently.

Thank you again for taking the time to reply.

I’d advise you to do a quick read on Erlang’s :persistent_term module. It’s absolutely perfect for rarely (or never) changing data.

Glad to help.

2 Likes

I ended up doing just this but on LUA: an object constructor loads a map with config parameters.Thanks @dimitarvp!