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Re: Is this quirky for a simple copy, editfiles operation?


From: Ed Brown
Subject: Re: Is this quirky for a simple copy, editfiles operation?
Date: Thu, 12 May 2005 17:02:33 -0600

On Thu, 2005-05-12 at 13:35, Mark Burgess wrote:
> In version 3 I hope that all of this
> will be handled more elegantly. 

Another tantalizing, yet mysterious, intimation of better things to
come.  One might start thinking you had a background in marketing!

Perhaps my concerns will be moot when cfengine 3 changes our current
paradigms, but when discussions about the ordering of actions in
cfengine become discussions about dependencies, I am really
disappointed.  While there is some overlap, they are different problems
really, and the change in semantics really changes the implications and
considerations.  The last time dependencies came up as a solution to the
limitations of the current actionsequence implentation, it appeared to
me to be more of a nod to notions of PC-ness (Programming Correct-ness),
than directed at solving the problems of system administrators, i.e.,
making cfengine even more flexible and easy to use.

Brendan's [extremely well-articulated and demonstrated] examples for
using class dependencies are interesting, but I'm not convinced that's
the answer to actionsequence limitations.  Imagine trying to implement
your current actionsequence in terms of class dependencies!  Granted, we
might not care to reinvent the actionsequence, and sequence might not
matter for much, even most, of what cfengine does.  (But knowing it is
determinate, and how, is often useful and important.)  

To me, it would be vastly easier, more powerful, and more flexible, to
simply assign a priority to an action (or not, if it doesn't matter),
and know immediately how it relates to ALL other actions, rather than
have to define any relationships individually.  I don't have to worry
about breaking dependencies, or finding/fixing/maintaining relationships
across many config files.   It's easy to understand at a glance for the
human and the machine parser.   Multiple passes aren't required...  (And
concerns, if there are any, about performance optimizations that a
dependency-based approach might offer, in my typical <10 second cfagent
run, would be way at the bottom of my list.)

Frankly, I prefer the status quo, to a solution based on defining
dependencies, at least as I understand the idea now.  

-Ed





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