Puppet users - Jan 2007 - Re: How to conditionally run defines? (and a question about updating... )

OK, too bad. I could work around it of course by adding
''unless'' and
''creates'' clauses on all the individual parts of the define
where
appropriate, but I think I''ll just ignore the warnings and overhead for
now.


It would be cool, though, if something like the ''unless'',
''onlyif'', etc,
logic was available for all resources (or at least, those where they make
some sense) as well as defines.

By the way... I''m not seeing the answer to this just now on the site:
to
update puppet to the next version just install the new version over the old
one? That''s how I''m doing it now, but I don''t know if
that will result in
stale files being left behind?

Thijs

On 15/01/07, Luke Kanies <luke@madstop.com> wrote:
>
> On Jan 16, 2007, at 1:38 AM, Thijs Oppermann wrote:
>
> > Hi all,
> >
> > Is there a (simple) way to add conditionals to a call to a define?
> > What I want is to run a define only if a file (that gets created
> > somewhere along the run of the define) does not exist. In this way I
> > can skip a whole lot of setup work in the define if I know it has
> > already run once before. I would think adding a unless clause would be
> > a elegant solution (and the other conditionals like onlyif that exist
> > elsewhere too).
> >
> > So that I can call my defines with something like this:
> >
> >     installesite { "testaa":
> >         require => [ perlinstall[ "everything" ], exec[
> > "fix-everything-sqldefs" ] ],
> >         unless  => "test -e /var/www/testaa/index.pl",
> >     }
> >
> > I don''t know if this would be easy to add to the puppet
language, or
> > if it can easily be emulated with code in the define itself?
I''m
> > drawing a bit of a blank on the last option at the moment... ;)
>
> At this point, there''s no real way to do this right now.
>
> You could kind of hack this right now, by having your definition have
> an exec at the beginning that will fail if the file exists, thus
> skipping the entire definition (because resources will be skipped if
> they have failed dependencies).  This will result in a lot of
> erroneous warnings, though.
>
> It seems that Puppet needs some kind of way to skip configuration
> branches, other than by throwing failures.  I''ll think about it,
but
> for now, you can''t do this, unfortunately.
>
>   --
>   I take my children everywhere, but they always find their way back
> home.
>               --Robert Orben
>   ---------------------------------------------------------------------
>   Luke Kanies | http://reductivelabs.com | http://madstop.com
>
>
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On Jan 16, 2007, at 10:17 AM, Thijs Oppermann wrote:
> OK, too bad. I could work around it of course by adding
''unless''
> and ''creates'' clauses on all the individual parts of the
define
> where appropriate, but I think I''ll just ignore the warnings and  
> overhead for now.
Okay.  I''m always looking for specific recommendations on how to  
better do this.  I agree it should be better, but I don''t know  
exactly how it should work.
> It would be cool, though, if something like the ''unless'',
''onlyif'',
> etc, logic was available for all resources (or at least, those  
> where they make some sense) as well as defines.
Yeah, I''ve often thought the same thing.  I''m a bit afraid of
some of
the repercussions, though, because it could tend to make  
configurations a lot more prone to instability and a lot less  
computable.  E.g., the same configuration could behave completely  
differently on machines that are almost but not quite the same, which  
is a bit frightening.  It''s fine to use them with execs because you  
have to have something like these parameters to make execs  
idempotent, but the rest of the resources are naturally idempotent,  
so these extra parameters would only be used for efficiency, which  
probably isn''t worth it, or for making widely diverging  
configurations, which is probably a very bad idea.
> By the way... I''m not seeing the answer to this just now on the  
> site: to update puppet to the next version just install the new  
> version over the old one? That''s how I''m doing it now,
but I don''t
> know if that will result in stale files being left behind?
I''d say that''s a packaging question, not a Puppet question per
se.
If you''re using Puppet''s installation script, then you
*should* be
okay just installing over it, but it''s far better to use native  
packages if they''re available.

  --
  It is well to remember that the entire universe, with one trifling
  exception, is composed of others.     --John Andrew Holmes
  ---------------------------------------------------------------------
  Luke Kanies | http://reductivelabs.com | http://madstop.com