[IPython-user] cluster file syntax

[Fernando Perez]

Brian Granger wrote:
> Fernando,
> 
> While we are making this change, do we want to also change the format
> of this file?  It would be nice to have it be human readable/editable.
>  My preference would have it be a valid python file, but I am not sure
> of the best way of doing this.  You have thought a lot more about
> config files than I have.  Any thoughts?

Well, the big question with config files is whether to use python itself as 
the language, or something else and parse it.  Brief comparison:

1. Use python.

Pros: no parsing required (well, we get it for free from python itself), 
extremely flexible for the users, they can put any logic they want.

Cons: security, mostly: arbitrary code can execute there.  And a little bit of 
potential complexity, as variables need to be declared in the file.


2. Use something else.

The easiest in terms of dependencies is the basic ConfigParser format:

http://docs.python.org/lib/module-ConfigParser.html

Pros: safe, easy to read and write.  Security is really the big plus.

Cons: more parsing involved, and more work to transform values defined in the 
file into python objects we need.  Less flexibility for users (it's a 
key/value file, not a programming language, so no logic allowed).


In this particular case, I'm not sure the security issue is that big of a 
deal, since this is a system to execute arbitrary python code anyway.  But 
given how paranoid one may want to be...

For ipython itself, I'm /definitely/ going with (1) in the future, but that's 
an easy one.  People load arbitrary code in their rc file anyway, it's just 
that today's system makes it inconvenient; I want it to be easy.

For the cluster config format, we could certainly go with (2) if you prefer to 
play it safe, even though it will be a tiny bit more work for us, and less 
flexible for users.

Thoughts?

f