[rudder-dev] Best Practises for writing techniques

[Michael Gliwinski]

Hmm, it appears my reply never got to the list.  In the meantime I got 
kidnapped for another project ;)  so I never noticed, sorry, re-sending now :)


On Thursday 28 Feb 2013 18:42:44 Jonathan Clarke wrote:
> On 28/02/13 18:31, Nicolas Charles wrote:
> > On 28/02/2013 12:31, Michael Gliwinski wrote:
> >> 1. prefixing variables with "rudder_" or "rudder_<technique_name>_";
> > 
> > That's a good point, maybe we've been overzealous on this convention.
> > I think we could use only rudder_ to prevent overly long variable names
> 
> Why use any prefix for variable names? Their scope is local to each
> bundle, so there is no risk of name collision. We can just called
> variables "thing", and since the bundles are all named
> "rudder_<technique_name>_*", the fully qualified variable name will
> contain rudder_, like "rudder_<technique_name>_*.thing".
> 
> Dropping the requirement to prefix variable names seems altogether more
> lightweight to me, making code easier to read, and not bringing any real
> risks.

+1 :)

> >> 3. config.st:
> >> 
> >> 3a. is the idea to aggregate various variables used within different
> >> bundles
> >> in a technique in one place?  (sounds neat)
> > 
> > Variables defined by Rudder must only go in this file, so yes, the
> > idea is to have all variables there
> 
> All *StringTemplate* variables from Rudder that is. However, any "pure"
> CFEngine variables should not be in this bundle, but in the main bundle
> that does stuff.
> 
> The intention behind this is to separate files so that some files
> contain *only* CFEngine code, with no Rudder specificities, in order
> that they could one day be reusable by simply calling the bundle via a
> CFEngine methods promises (think one Technique depending on another...).
> So this way, we put all Rudder specific stuff (String Template variables
> and reporting) in separate bundles.
> 
> This should also encourage code sharing with pure-CFEngine users.

That sounds great!

Would you oppose to calling it with some more descriptive name then?  Like 
rudder_main or technique_main, etc.?  Just thinking something more intuitive 
would be useful given that it is actually an entry point for Rudder, and not 
only configuration.

> Thanks for your comments Michael, it's great to see your interest and
> have some feedback on this! By the way, if you like, we can give you
> write access to the wiki page, so you can clarify some of these points
> if you'd like?

Sure, I think I've got a better grasp on things now, so I can make some edits 
and let you know so you can review.

Thanks!

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