On 30 August 2013 09:55, Luke Kanies <[email protected]> wrote: > On Aug 30, 2013, at 1:05 AM, "R.I.Pienaar" <[email protected]> wrote: > > > > > > > ----- Original Message ----- > >> From: "Luke Kanies" <[email protected]> > >> To: [email protected] > >> 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 <[email protected] > > > >> 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 <[email protected]> > wrote: > >>> On Aug 28, 2013, at 12:38 PM, Andy Parker <[email protected]> > wrote: > >>>> On Wed, Aug 28, 2013 at 10:20 AM, Luke Kanies <[email protected]> > >>>> wrote: > >>>> On Aug 28, 2013, at 8:45 AM, Andy Parker <[email protected]> > 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) > I.e., there's nothing to work around in this case, it already works. > > The anchor bug is something you actually have to work around. > > > Also I think fixing this only for the new resource like syntax and not > for > > include would be a mistake - though i can see why that would be the > chosen > > path as doing it otherwise would easily create loops etc. > > I don't know where this is coming from; I made no mention of > differentiating between the two, and I can't imagine a solution that would > or could do so. > > -- > Luke Kanies | http://about.me/lak | http://puppetlabs.com/ | > +1-615-594-8199 > > -- > You received this message because you are subscribed to the Google Groups > "Puppet Developers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/puppet-dev. > For more options, visit https://groups.google.com/groups/opt_out. > -- Erik Dalén -- You received this message because you are subscribed to the Google Groups "Puppet Developers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/puppet-dev. For more options, visit https://groups.google.com/groups/opt_out.
