Puppet users - Oct 2012 - anchor pattern and class containment status

All-

We''re currently using puppet 2.7.14 on master and all clients.

I thought I understood why ''anchor'' is part of stdlib, but
after
re-reading both

 	http://projects.puppetlabs.com/projects/puppet/wiki/Anchor_Pattern

and

 	http://projects.puppetlabs.com/issues/8040

yesterday in preparation for trying to explain it to one of our team
that''s coming up to speed on puppet, now I''m not so certain I
really
understand.

Specifically, is it necessary to use the anchor pattern if your module
only defines resources and doesn''t require or include any other
classes?

For example, if I have

class benthic {

   group { ''squarepants'':
     ensure => present,
     gid    => ''99999'',
   }

   user { ''spongebob'':
     ensure => present,
     uid    => ''99999'',
     gid    => ''squarepants'',
     home   => ''/home/pineapple'',
   }

   package { ''starfish'':
     ensure => present,
   }

   file { ''/etc/starfish.conf'':
     ensure  => file,
     owner   => ''root'',
     group   => ''squarepants'',
     mode    => ''0640'',
     source  => ''puppet:///benthic/starfish.conf'',
     require => [
       Package[''starfish''],
       User[''spongebob''],
     ],
   }

   service { ''i_m_ready'',
     ensure  => running,
     enable  => true,
     require => Package[''starfish''],
   }
}

Given that class, do I need to use anchors to ensure that the
group/user/package/file/service resource graph is correctly attached to
(contained within) Class[''benthic''], so that if some other
module does

   someresource { ''whatever'':
     ...
     require => Class[''benthic''],
   }

it just works, or, should I augment my class to also have

     anchor { ''benthic::begin'': }
     anchor { ''benthic::end'': }

     Anchor[''benthic::begin''] ->
Group[''squarepants'']
     Service[''i_m_ready''] ->
Anchor[''benthic::end'']

?

My resources within the class are using explicit "require" when
necessary
and relying on puppet''s automatic "require" logic in other
places so
they are correctly ordered, but it''s not clear from the pattern
document
in the wiki or the ticket whether the issue is solely with nested
classes, or whether it''s important to also use the pattern for standard
resources.

Also, the ticket was with respect to 2.6.  I know this hasn''t changed
for
2.7, but is there anything in 3.0 that addresses the issue?

Tim
-- 
Tim Mooney                                             Tim.Mooney@ndsu.edu
Enterprise Computing & Infrastructure                  701-231-1076 (Voice)
Room 242-J6, IACC Building                             701-231-8541 (Fax)
North Dakota State University, Fargo, ND 58105-5164

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On Wed, Oct 3, 2012 at 2:57 PM, Tim Mooney <Tim.Mooney@ndsu.edu> wrote:
>
> All-
>
> We''re currently using puppet 2.7.14 on master and all clients.
>
> I thought I understood why ''anchor'' is part of stdlib,
but after
> re-reading both
>
>         http://projects.puppetlabs.**com/projects/puppet/wiki/**
>
Anchor_Pattern<http://projects.puppetlabs.com/projects/puppet/wiki/Anchor_Pattern>
>
> and
>
>        
http://projects.puppetlabs.**com/issues/8040<http://projects.puppetlabs.com/issues/8040>
>
> yesterday in preparation for trying to explain it to one of our team
> that''s coming up to speed on puppet, now I''m not so
certain I really
> understand.
>
yep, its probably the most confusing part of Puppet :(

>
> Specifically, is it necessary to use the anchor pattern if your module
> only defines resources and doesn''t require or include any other
classes?
>
you only have to use the anchor pattern when you need to depend on a class
that has classes defined in it. The example below does not need the anchor
pattern.

> For example, if I have
>
> class benthic {
>
>   group { ''squarepants'':
>     ensure => present,
>     gid    => ''99999'',
>   }
>
>   user { ''spongebob'':
>     ensure => present,
>     uid    => ''99999'',
>     gid    => ''squarepants'',
>     home   => ''/home/pineapple'',
>   }
>
>   package { ''starfish'':
>     ensure => present,
>   }
>
>   file { ''/etc/starfish.conf'':
>     ensure  => file,
>     owner   => ''root'',
>     group   => ''squarepants'',
>     mode    => ''0640'',
>     source  => ''puppet:///benthic/starfish.**conf'',
>     require => [
>       Package[''starfish''],
>       User[''spongebob''],
>     ],
>   }
>
>   service { ''i_m_ready'',
>     ensure  => running,
>     enable  => true,
>     require => Package[''starfish''],
>   }
> }
>
> Given that class, do I need to use anchors to ensure that the
> group/user/package/file/**service resource graph is correctly attached to
> (contained within) Class[''benthic''], so that if some
other module does
>
>   someresource { ''whatever'':
>     ...
>     require => Class[''benthic''],
>   }
>
> it just works, or, should I augment my class to also have
>
>     anchor { ''benthic::begin'': }
>     anchor { ''benthic::end'': }
>
>     Anchor[''benthic::begin''] ->
Group[''squarepants'']
>     Service[''i_m_ready''] ->
Anchor[''benthic::end'']
>
> ?
>
> My resources within the class are using explicit "require" when
necessary
> and relying on puppet''s automatic "require" logic in
other places so they
> are correctly ordered, but it''s not clear from the pattern
document
> in the wiki or the ticket whether the issue is solely with nested
> classes, or whether it''s important to also use the pattern for
standard
> resources.
>
> Also, the ticket was with respect to 2.6.  I know this hasn''t
changed for
> 2.7, but is there anything in 3.0 that addresses the issue?
>
> Tim
> --
> Tim Mooney                                             Tim.Mooney@ndsu.edu
> Enterprise Computing & Infrastructure                 
701-231-1076(Voice)
> Room 242-J6, IACC Building                             701-231-8541 (Fax)
> North Dakota State University, Fargo, ND 58105-5164
>
> --
> You received this message because you are subscribed to the Google Groups
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>
group/puppet-users?hl=en<http://groups.google.com/group/puppet-users?hl=en>
> .
>
>
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On Wednesday, October 3, 2012 4:59:58 PM UTC-5, Tim Mooney
wrote:
>
>
> All- 
>
> We''re currently using puppet 2.7.14 on master and all clients. 
>
> I thought I understood why ''anchor'' is part of stdlib,
but after
> re-reading both 
>
>          
> http://projects.puppetlabs.com/projects/puppet/wiki/Anchor_Pattern 
>
> and 
>
>          http://projects.puppetlabs.com/issues/8040 
>
> yesterday in preparation for trying to explain it to one of our team 
> that''s coming up to speed on puppet, now I''m not so
certain I really
> understand. 
>
> Specifically, is it necessary to use the anchor pattern if your module 
> only defines resources and doesn''t require or include any other
classes?
>

No, not as I understand it.  The problem is that in Puppet 2.6 and maybe 
2.7, classes are not directly represented in the relationship graph.  
Therefore, if you declare a relationship where one end is a class, it 
appears in the graph as a collection of relationships with the resources 
declared by that class.  If both ends are classes then you get n x m 
relationships, where n and m are the numbers of resources declared by the 
two classes.

The need for the anchor pattern arises because the generated relationships 
to a class Foo''s resources do not include relationships to resources 
declared by classes declared in the body of Foo, and because declaring a 
class (except via the ''require'' function) does not create a
relationship
between the declaring and declared classes.

The anchor pattern involves using relationships to resources declared 
directly by Foo to bound the application order of classes declared by Foo.  
Anchors are not needed for resources declared directly by Foo (else the 
anchor pattern wouldn''t work in the first place).  The stdlib provides
the
special ''anchor'' resource type specifically for this purpose,
but resources
of any other type could be used as well.

If Foo does not declare any other classes, then it gains no advantage from 
the anchor pattern.  If the needed ordering of interclass relationships is 
declared some other way, then the anchor pattern is unneeded.  If and when 
classes gain direct representation in the relationship graph (maybe
it''s
happened already?), with (optional?) relationships to their included 
classes, the anchor pattern will no longer be needed.


John

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On Wed, Oct 3, 2012 at 2:57 PM, Tim Mooney <Tim.Mooney@ndsu.edu>
wrote:
> I thought I understood why ''anchor'' is part of stdlib,
but after
> re-reading both
I suspect Dan & John have covered this well enough for you but I
wanted to point out a nice piece of the Puppet reference manual that
covers this.
http://docs.puppetlabs.com/puppet/2.7/reference/lang_containment.html#known-issues

It explains things better than I ever could. If it''s still not clear
enough, please consider filing a ticket against our docs for
improvement: https://projects.puppetlabs.com/projects/puppet-docs

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In regard to: Re: [Puppet Users] anchor pattern and class containment...:
> On Wed, Oct 3, 2012 at 2:57 PM, Tim Mooney <Tim.Mooney@ndsu.edu>
wrote:
>
>>
>> All-
>>
>> We''re currently using puppet 2.7.14 on master and all clients.
>>
>> I thought I understood why ''anchor'' is part of
stdlib, but after
>> re-reading both
>>
>>         http://projects.puppetlabs.**com/projects/puppet/wiki/**
>>
Anchor_Pattern<http://projects.puppetlabs.com/projects/puppet/wiki/Anchor_Pattern>
>>
>> and
>>
>>        
http://projects.puppetlabs.**com/issues/8040<http://projects.puppetlabs.com/issues/8040>
>>
>> yesterday in preparation for trying to explain it to one of our team
>> that''s coming up to speed on puppet, now I''m not so
certain I really
>> understand.
>>
>
> yep, its probably the most confusing part of Puppet :(
:-)  I think I would vote for create_resources() in that competition.
>> Specifically, is it necessary to use the anchor pattern if your module
>> only defines resources and doesn''t require or include any
other classes?
>>
>
> you only have to use the anchor pattern when you need to depend on a class
> that has classes defined in it. The example below does not need the anchor
> pattern.
Thanks Dan!  The info from you & John & Ryan has been very helpful.

Tim
-- 
Tim Mooney                                             Tim.Mooney@ndsu.edu
Enterprise Computing & Infrastructure                  701-231-1076 (Voice)
Room 242-J6, IACC Building                             701-231-8541 (Fax)
North Dakota State University, Fargo, ND 58105-5164

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In regard to: Re: [Puppet Users] anchor pattern and class containment...:
> On Wed, Oct 3, 2012 at 2:57 PM, Tim Mooney <Tim.Mooney@ndsu.edu>
wrote:
>> I thought I understood why ''anchor'' is part of
stdlib, but after
>> re-reading both
>
> I suspect Dan & John have covered this well enough for you but I
> wanted to point out a nice piece of the Puppet reference manual that
> covers this.
http://docs.puppetlabs.com/puppet/2.7/reference/lang_containment.html#known-issues
Thanks Ryan, and thanks especially for the rewritten reference.  I
haven''t
been through all of it yet, but the parts I''ve seen are excellent.
> It explains things better than I ever could. If it''s still not
clear
> enough, please consider filing a ticket against our docs for
> improvement: https://projects.puppetlabs.com/projects/puppet-docs
I created

   https://projects.puppetlabs.com/issues/16783

which mentions what I think might be a bug in the second example on that
page and also asks for a little clarification.

Thanks again for the pointer to the docs!

Tim
-- 
Tim Mooney                                             Tim.Mooney@ndsu.edu
Enterprise Computing & Infrastructure                  701-231-1076 (Voice)
Room 242-J6, IACC Building                             701-231-8541 (Fax)
North Dakota State University, Fargo, ND 58105-5164

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