----- Original Message -----
> From: "Erik Dalén" <erik.gustav.da...@gmail.com>
> To: "Puppet Developers" <puppet-dev@googlegroups.com>
> Sent: Friday, August 30, 2013 5:07:46 PM
> Subject: Re: Anchor pattern (was Re: [Puppet-dev] Puppet 4 discussions)
>
> On 30 August 2013 09:55, Luke Kanies <l...@puppetlabs.com> wrote:
>
> > On Aug 30, 2013, at 1:05 AM, "R.I.Pienaar" <r...@devco.net> wrote:
> >
> > >
> > >
> > > ----- Original Message -----
> > >> From: "Luke Kanies" <l...@puppetlabs.com>
> > >> To: puppet-dev@googlegroups.com
> > >> Sent: Thursday, August 29, 2013 11:27:00 PM
> > >> Subject: Re: Anchor pattern (was Re: [Puppet-dev] Puppet 4 discussions)
> > >>
> > >> On Aug 29, 2013, at 12:24 PM, John Bollinger <john.bollin...@stjude.org
> > >
> > >> wrote:
> > >>
> > >>>
> > >>>
> > >>> On Wednesday, August 28, 2013 5:56:45 PM UTC-5, Andy Parker wrote:
> > >>> On Wed, Aug 28, 2013 at 3:22 PM, Luke Kanies <lu...@puppetlabs.com>
> > wrote:
> > >>> On Aug 28, 2013, at 12:38 PM, Andy Parker <an...@puppetlabs.com>
> > wrote:
> > >>>> On Wed, Aug 28, 2013 at 10:20 AM, Luke Kanies <lu...@puppetlabs.com>
> > >>>> wrote:
> > >>>> On Aug 28, 2013, at 8:45 AM, Andy Parker <an...@puppetlabs.com>
> > wrote:
> > >>>>
> > >>>>> * #8040 - anchor pattern. I think a solution is in sight, but it
> > >>>>> didn't make 3.3.0 and it is looking like it might be backwards
> > >>>>> incompatible.
> > >>>>
> > >>>> Why would it be incompatible?
> > >>>>
> > >>>> That implies that we can't ship it until 4.0, which would be a tragedy
> > >>>> worth fighting hard to avoid.
> > >>>>
> > >>>>
> > >>>> The only possible problem, that I know of, would be that it would
> > change
> > >>>> the evaluation order. Once things get contained correctly that might
> > >>>> cause problems. We never give very strong guarantees between versions
> > of
> > >>>> puppet, but given the concern with manifest order, I thought that I
> > would
> > >>>> call this out as well.
> > >>>
> > >>> Do you mean, for 2 classes that should have a relationship but
> > currently
> > >>> don't because of the bug (and the lack of someone using an anchor
> > pattern
> > >>> to work around the bug), fixing that bug would cause them to have a
> > >>> relationship and thus change the order?
> > >>>
> > >>>
> > >>> No that shouldn't be a problem. I think we will be using making the
> > >>> resource syntax for classes ( class { foo: } ) create the containment
> > >>> relationship. That doesn't allow multiple declarations and so we
> > shouldn't
> > >>> encounter the problem of the class being in two places.
> > >>>
> > >>>
> > >>> But it does allow multiple declarations, so long as only the first one
> > >>> parsed uses the parameterized syntax. There can be any number of other
> > >>> places where class foo is declared via the include() function or
> > require()
> > >>> function.
> > >>>
> > >>>
> > >>> That is, you're concerned that the bug has been around so long it's
> > >>> considered a feature, and thus we can't change it except in a major
> > >>> release?
> > >>>
> > >>>
> > >>> More of just that the class will start being contained in another
> > class and
> > >>> so it will change where it is evaluated in an agent run. That could
> > cause
> > >>> something that worked before to stop working (it only worked before
> > >>> because of random luck). I'm also, right now, wondering if there are
> > >>> possible dependency cycles that might show up. I haven't thought that
> > one
> > >>> through.
> > >>>
> > >>>
> > >>> Yes, it is possible that dependency cycles could be created where none
> > >>> existed before. About a week ago I added an example to the comments
> > >>> thread on this issue; it is part of a larger objection to the proposed
> > >>> solution: http://projects.puppetlabs.com/issues/8040#note-35. I also
> > >>> included a proposed alternative solution that could go into Puppet 3.
> > >>
> > >> As mentioned in my other email, the solution to this problem should not
> > in
> > >> any way require changes to containment semantics, and certainly
> > shouldn't
> > >> require class evaluation to indicate class containment. As I said, it
> > used
> > >> to do that for the first instance (but not for second, which led to some
> > >> inconsistencies and surprises, which is why I removed it). These days,
> > >> though, in general classes only contain resources, not other classes.
> > What
> > >
> > > I am not sure I follow and have missed some of this thread while on hols
> > but
> > > here is why people use the anchor pattern:
> > >
> > > class one {
> > > include two
> > >
> > > notify{$name: }
> > > }
> > >
> > > class two {
> > > notify{$name: }
> > > }
> > >
> > > class three {
> > > notify{$name: require => Class["one"]}
> > > }
> > >
> > > include one, three
> > >
> > > $ puppet apply test.pp
> > > Notice: /Stage[main]/One/Notify[one]/message: defined 'message' as 'one'
> > > Notice: /Stage[main]/Three/Notify[three]/message: defined 'message' as
> > 'three'
> > > Notice: /Stage[main]/Two/Notify[two]/message: defined 'message' as 'two'
> > > Notice: Finished catalog run in 0.11 seconds
> > >
> > > The desired outcome is that Notify[two] is before Notify[three]
> > >
> > > So unless I am reading you wrong, the anchor pattern is used
> > specifically because
> > > today many people have classes contained in other classes and it does
> > not work
> > > as desired.
> >
> > If you want a specific order, there are plenty of tools for achieving
> > that; in this particular case, you should use 'require two' instead of
> > 'include two' (or include it, then use something like Class[two] ->
> > Class[three], but…)
> >
>
> Changing the include to require will cause "two" to happen before "one",
> which is correct behaviour.
>
> Just adding Class[two] -> Class[three] inside class one fixes the order
> though without using any anchors (in this example at least)
Sure, are you suggesting everyone who download a module from the forge study
its internals, find all its contained classes and add these just so that
require => Class["forge_module"]
will "work"?
In the example consider class one and two to be part of a forge module, and
three to be my site specific module that I wish to have a dependency on the
entirety of the forge module.
The actual comments in anchor explains this well see
https://github.com/puppetlabs/puppetlabs-stdlib/blob/master/lib/puppet/type/anchor.rb
I want to just be able to say Class["ntp"] -> Class["mysql"] and not have to
be concerned with the inner workings of the ntp module - here in the comments
using 3 contained classes
The only way today to do that is by adding all these anchor things - and that's
the bug that leads to a horrible user experience and 100s of unneeded resources
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