----- Original Message ----- > From: "Luke Kanies" <[email protected]> > To: [email protected] > Sent: Friday, August 30, 2013 6:34:13 PM > Subject: Re: Anchor pattern (was Re: [Puppet-dev] Puppet 4 discussions) > > On Aug 30, 2013, at 9:14 AM, "R.I.Pienaar" <[email protected]> wrote: > > > > > > > ----- Original Message ----- > >> From: "Erik Dalén" <[email protected]> > >> To: "Puppet Developers" <[email protected]> > >> 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 <[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) > > > > 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"? > > No, I'm suggesting that everyone who builds a module actually set up > appropriate dependencies between the classes. If you've got a top-level > class, it should be listed as requiring the classes it requires. Shouldn't > the module author be responsible for getting that right? > > The only other reasonable choice I can come up with is to create something > like a 'package' type, where any kind of class declaration (either with > 'include' or 'class {}') results in a containment relationship. That's more > of a feature than a bug thing, right?
Then we're not on the same page, when people want the anchor pattern gone they want what you're calling the feature implemented. >From Andy's earlier email here - that's what he also think. If this is up to the module author - as it is today - then what you're promoting is a scenario where 100s of LOC is dedicated to code thats there for no other reason than to facilitate ordering and containment and this is a missfeature. People do not understand it, do not anticipate the current behavior and its hurting the ability to make reusable modules easily. > > > 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 > > Why can't you use requires? Because requires is requires and not contains. class one { include two notify{$name: } } should contain Class[two] the same way it contains Notify[one] - and thus all the resources in two and any classes it includes and so forth and so on. But as Andy explains in detail and I only hinted at this leads to trivial loops unless we only do this with the resource like includes. -- 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.
