thr3ads.net - Puppet users - [Puppet Users] Is accessing vars from different class safe? [Aug 2011]

If this information is useful, please help other people find it:
Share via:

Stefan Schulte

2011-Aug-06 14:14 UTC

[Puppet Users] Is accessing vars from different class safe?

Hi puppet users,

I have a question about crossdependencies. Let''s say I want to manage
an
application my_application and the backupclient on a node. I always need
a backclient but its configuration depends on
a) wether my_application is installed or not
b) the configuration of my_application

This is one pattern I can think of:

    node ''mynode'' {
      class { ''my_application'':
        paramA => valueA,
        paramBalsoInterestingForBackupclass => valueB,
        paramCalsoInterestingForBackupclass => valueC,
      }
      class { ''backup::client'':
        backup_definitions => [ ''my_application'' ],
      }
    }


Is it ALWAYS safe to access $::my_application::paramBalsoInterestingForBackup
inside the backup::client class or can I run into ordering issues?

Or how whould you model this kind of relationship? A second pattern I
can think of is having a third class backup::client::my_application that
takes the same params as the my_application class and gets included
inside the my_application class. So I would end up with

    node ''mynode'' {
      class { ''my_application'':
        paramA => valueA,
        paramBalsoInterestingForBackupclass => valueB,
        paramCalsoInterestingForBackupcalss => valueC,
        backup => true,
      }
      class { ''backup::client'': } # just the basic config
    }

and inside class my_application:

    if $backup {
      class { ''backup::client::my_application'':
        paramB  => $paramBalsoInterestingForBackupclass,
        paramC  => $paramCalsoInterestingForBackupclass,
        require => Class[''backup::client''],
      }
    }

Does this sound like a better approach? Nevertheless is the first one
save?

-Stefan

John Martin

2011-Aug-06 23:27 UTC

head link

[Puppet Users] Re: Is accessing vars from different class safe?

It doesn''t sound safe since it sounds like you don''t alway
install the
class.   I would lean towards a configuratios class that you can
reference to determine if it is or will be installed.  I would pass in
that value as a parameter to the backup class instead on internally
referencing across classes as well. One last thing would be to use a
"require config_class" statement before attempting to access the
config var.

John

-- 
You received this message because you are subscribed to the Google Groups
"Puppet Users" group.
To post to this group, send email to puppet-users@googlegroups.com.
To unsubscribe from this group, send email to
puppet-users+unsubscribe@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/puppet-users?hl=en.

Stefan Schulte

2011-Aug-11 15:26 UTC

head link

Re: [Puppet Users] Is accessing vars from different class safe?

On Sat, Aug 06, 2011 at 04:14:31PM +0200, Stefan Schulte
wrote:> Is it ALWAYS safe to access
$::my_application::paramBalsoInterestingForBackup
> inside the backup::client class or can I run into ordering issues?
At least I can answer this question my self: It is not safe, you can end
up with

2 Modules with one class each

    class mod1::class1($message) {
      $messag = $message
      notice $message 
    }
    class mod2::class2 {
      notice $mod1::class1::message
    }

1 Manifest

    class { ''mod2::class2'': }
    class { ''mod1::class1'': message => ''Hallo
Welt''}

Output

warning: Scope(Class[Mod2::Class2]): Could not look up qualified
variable ''mod1::class1::message''; class mod1::class1 has not
been
evaluated at /tmp/modules/mod2/manifests/class2.pp:2
notice: Scope(Class[Mod2::Class2]): 
notice: Scope(Class[Mod1::Class1]): Hallo Welt
info: Applying configuration version ''1313075940''
notice: Finished catalog run in 0.16 seconds


-Stefan

Aaron Grewell

2011-Aug-11 15:30 UTC

head link

Re: [Puppet Users] Is accessing vars from different class safe?

It''s fine, just make sure class2 requires class1.  That''s what
requires are
for.

On Thu, Aug 11, 2011 at 8:26 AM, Stefan Schulte <
stefan.schulte@taunusstein.net> wrote:
> On Sat, Aug 06, 2011 at 04:14:31PM +0200, Stefan Schulte wrote:
> > Is it ALWAYS safe to access
> $::my_application::paramBalsoInterestingForBackup
> > inside the backup::client class or can I run into ordering issues?
>
> At least I can answer this question my self: It is not safe, you can end
> up with
>
> 2 Modules with one class each
>
>    class mod1::class1($message) {
>      $messag = $message
>      notice $message
>    }
>    class mod2::class2 {
>      notice $mod1::class1::message
>    }
>
> 1 Manifest
>
>    class { ''mod2::class2'': }
>    class { ''mod1::class1'': message => ''Hallo
Welt''}
>
> Output
>
> warning: Scope(Class[Mod2::Class2]): Could not look up qualified
> variable ''mod1::class1::message''; class mod1::class1 has
not been
> evaluated at /tmp/modules/mod2/manifests/class2.pp:2
> notice: Scope(Class[Mod2::Class2]):
> notice: Scope(Class[Mod1::Class1]): Hallo Welt
> info: Applying configuration version ''1313075940''
> notice: Finished catalog run in 0.16 seconds
>
>
> -Stefan
>
-- 
You received this message because you are subscribed to the Google Groups
"Puppet Users" group.
To post to this group, send email to puppet-users@googlegroups.com.
To unsubscribe from this group, send email to
puppet-users+unsubscribe@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/puppet-users?hl=en.

Stefan Schulte

2011-Aug-11 15:54 UTC

head link

Re: [Puppet Users] Is accessing vars from different class safe?

On Thu, Aug 11, 2011 at 08:30:37AM -0700, Aaron Grewell
wrote:> It''s fine, just make sure class2 requires class1.  That''s
what requires are
> for.
> 
Unfortunately it still doesnt worked. Changed class2 to

    class mod2::class2 {
      file { $mod1::class1::message:
        ensure  => file,
        require => Class[''mod1::class1''],
      }
    }

Manifest is still

    class { ''mod2::class2'': }
    class { ''mod1::class1'': message => ''Hallo
Welt''}

What I get is

warning: Scope(Class[Mod2::Class2]): Could not look up qualified
variable ''mod1::class1::message''; class mod1::class1 has not
been
evaluated at /tmp/modules/mod2/manifests/class2.pp:2

notice: Scope(Class[Mod1::Class1]): Hallo Welt

Parameter path failed: File paths must be fully qualified, not
''undef''
at /tmp/modules/mod2/manifests/class2.pp:5

If I change the order in the manifest it works.

-Stefan> On Thu, Aug 11, 2011 at 8:26 AM, Stefan Schulte <
> stefan.schulte@taunusstein.net> wrote:
> 
> > On Sat, Aug 06, 2011 at 04:14:31PM +0200, Stefan Schulte wrote:
> > > Is it ALWAYS safe to access
> > $::my_application::paramBalsoInterestingForBackup
> > > inside the backup::client class or can I run into ordering
issues?
> >
> > At least I can answer this question my self: It is not safe, you can
end
> > up with
> >
> > 2 Modules with one class each
> >
> >    class mod1::class1($message) {
> >      $messag = $message
> >      notice $message
> >    }
> >    class mod2::class2 {
> >      notice $mod1::class1::message
> >    }
> >
> > 1 Manifest
> >
> >    class { ''mod2::class2'': }
> >    class { ''mod1::class1'': message =>
''Hallo Welt''}
> >
> > Output
> >
> > warning: Scope(Class[Mod2::Class2]): Could not look up qualified
> > variable ''mod1::class1::message''; class mod1::class1
has not been
> > evaluated at /tmp/modules/mod2/manifests/class2.pp:2
> > notice: Scope(Class[Mod2::Class2]):
> > notice: Scope(Class[Mod1::Class1]): Hallo Welt
> > info: Applying configuration version ''1313075940''
> > notice: Finished catalog run in 0.16 seconds
> >
> >
> > -Stefan
> >
> 
> -- 
> You received this message because you are subscribed to the Google Groups
"Puppet Users" group.
> To post to this group, send email to puppet-users@googlegroups.com.
> To unsubscribe from this group, send email to
puppet-users+unsubscribe@googlegroups.com.
> For more options, visit this group at
http://groups.google.com/group/puppet-users?hl=en.
>

Aaron Grewell

2011-Aug-11 16:23 UTC

head link

Re: [Puppet Users] Is accessing vars from different class safe?

I think you''ll have to do it at the class level with the arrow
operators
rather than at the resource level.  I haven''t ever done that, but I
think if
the manifest contains something like:

   class { ''mod2::class2'': }
   class { ''mod1::class1'': message => ''Hallo
Welt''}
   mod1 -> mod2

you may have better luck.

On Thu, Aug 11, 2011 at 8:54 AM, Stefan Schulte <
stefan.schulte@taunusstein.net> wrote:
> On Thu, Aug 11, 2011 at 08:30:37AM -0700, Aaron Grewell wrote:
> > It''s fine, just make sure class2 requires class1. 
That''s what requires
> are
> > for.
> >
>
> Unfortunately it still doesnt worked. Changed class2 to
>
>    class mod2::class2 {
>      file { $mod1::class1::message:
>        ensure  => file,
>        require => Class[''mod1::class1''],
>      }
>    }
>
> Manifest is still
>
>    class { ''mod2::class2'': }
>    class { ''mod1::class1'': message => ''Hallo
Welt''}
>
> What I get is
>
> warning: Scope(Class[Mod2::Class2]): Could not look up qualified
> variable ''mod1::class1::message''; class mod1::class1 has
not been
> evaluated at /tmp/modules/mod2/manifests/class2.pp:2
>
> notice: Scope(Class[Mod1::Class1]): Hallo Welt
>
> Parameter path failed: File paths must be fully qualified, not
''undef''
> at /tmp/modules/mod2/manifests/class2.pp:5
>
> If I change the order in the manifest it works.
>
> -Stefan
> > On Thu, Aug 11, 2011 at 8:26 AM, Stefan Schulte <
> > stefan.schulte@taunusstein.net> wrote:
> >
> > > On Sat, Aug 06, 2011 at 04:14:31PM +0200, Stefan Schulte wrote:
> > > > Is it ALWAYS safe to access
> > > $::my_application::paramBalsoInterestingForBackup
> > > > inside the backup::client class or can I run into ordering
issues?
> > >
> > > At least I can answer this question my self: It is not safe, you
can
> end
> > > up with
> > >
> > > 2 Modules with one class each
> > >
> > >    class mod1::class1($message) {
> > >      $messag = $message
> > >      notice $message
> > >    }
> > >    class mod2::class2 {
> > >      notice $mod1::class1::message
> > >    }
> > >
> > > 1 Manifest
> > >
> > >    class { ''mod2::class2'': }
> > >    class { ''mod1::class1'': message =>
''Hallo Welt''}
> > >
> > > Output
> > >
> > > warning: Scope(Class[Mod2::Class2]): Could not look up qualified
> > > variable ''mod1::class1::message''; class
mod1::class1 has not been
> > > evaluated at /tmp/modules/mod2/manifests/class2.pp:2
> > > notice: Scope(Class[Mod2::Class2]):
> > > notice: Scope(Class[Mod1::Class1]): Hallo Welt
> > > info: Applying configuration version
''1313075940''
> > > notice: Finished catalog run in 0.16 seconds
> > >
> > >
> > > -Stefan
> > >
> >
> > --
> > You received this message because you are subscribed to the Google
Groups
> "Puppet Users" group.
> > To post to this group, send email to puppet-users@googlegroups.com.
> > To unsubscribe from this group, send email to
> puppet-users+unsubscribe@googlegroups.com.
> > For more options, visit this group at
> http://groups.google.com/group/puppet-users?hl=en.
> >
>
-- 
You received this message because you are subscribed to the Google Groups
"Puppet Users" group.
To post to this group, send email to puppet-users@googlegroups.com.
To unsubscribe from this group, send email to
puppet-users+unsubscribe@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/puppet-users?hl=en.

Stefan Schulte

2011-Aug-11 16:55 UTC

head link

Re: [Puppet Users] Is accessing vars from different class safe?

On Thu, Aug 11, 2011 at 09:23:51AM -0700, Aaron Grewell
wrote:> I think you''ll have to do it at the class level with the arrow
operators
> rather than at the resource level.  I haven''t ever done that, but
I think if
> the manifest contains something like:
> 
>    class { ''mod2::class2'': }
>    class { ''mod1::class1'': message => ''Hallo
Welt''}
>    mod1 -> mod2
> 
> you may have better luck.
Nope. Neither does

    class { ''mod2::class2'': require =>
Class[''mod1::class1'']}
    class { ''mod1::class1'': message => ''Hallo
Welt''}

nor does


  class { ''mod2::class2'': require =>
Class[''mod2::class2'']}
  class { ''mod1::class1'': message => ''Hallo
Welt''}

  Class[''mod1::class1''] ->
Class[''mod2::class2'']

work.

So you basically run into the same issues as when you use the defined
function to check for other classes inside a class: It all depends on
the parsing order. At least I get a warning if the order in my manifest
is wrong:

    warning: Scope(Class[Mod2::Class2]): Could not look up qualified
    variable ''mod1::class1::message''; class mod1::class1 has
not been
    evaluated at /tmp/modules/mod2/manifests/class2.pp:2

but unfortunately puppet does not fail hard here but just applies a
catalog with some empty variables which in my opinion is just wrong.

-Stefan

jcbollinger

2011-Aug-11 21:30 UTC

head link

[Puppet Users] Re: Is accessing vars from different class safe?

On Aug 11, 10:54 am, Stefan Schulte <stefan.schu...@taunusstein.net>
wrote:> On Thu, Aug 11, 2011 at 08:30:37AM -0700, Aaron Grewell wrote:
> > It''s fine, just make sure class2 requires class1.
 That''s what requires are
> > for.
>
> Unfortunately it still doesnt worked. Changed class2 to
>
>     class mod2::class2 {
>       file { $mod1::class1::message:
>         ensure  => file,
>         require => Class[''mod1::class1''],
>       }
>     }
>
> Manifest is still
>
>     class { ''mod2::class2'': }
>     class { ''mod1::class1'': message => ''Hallo
Welt''}
>
> What I get is
>
> warning: Scope(Class[Mod2::Class2]): Could not look up qualified
> variable ''mod1::class1::message''; class mod1::class1 has
not been
> evaluated at /tmp/modules/mod2/manifests/class2.pp:2

I must say I''m not surprised that one didn''t work.  Indeed, I
would
have been surprised if it had.  The require is inside a scope defined
by the variable in question, and that scope can''t be defined in the
first place.

I think I know what''s going on.  Basically, ''require''
and its friends
are the the wrong tool for the job: they establish order relationships
for determining the order in which resources are *applied* by the
agent, but they not necessarily the order in which resources are
evaluated during catalog compilation by the master.

Were class1 not parameterized, I would recommend that class2 simply
''include'' it, and I am confident that would make it all good. 
But you
cannot do that with a parameterized class (as far as I am aware), so I
think that leaves you up a creek.

John
Parameterized Classes -- Finding new ways to break your manifests
since 2010!

-- 
You received this message because you are subscribed to the Google Groups
"Puppet Users" group.
To post to this group, send email to puppet-users@googlegroups.com.
To unsubscribe from this group, send email to
puppet-users+unsubscribe@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/puppet-users?hl=en.

Aaron Grewell

2011-Aug-11 22:05 UTC

head link

Re: [Puppet Users] Re: Is accessing vars from different class safe?

Thanks John ,  I wasn''t aware of that distinction.  I suspect
you''ve saved
me a forehead=>wall session on down the road. :-)
On Aug 11, 2011 2:31 PM, "jcbollinger"
<John.Bollinger@stjude.org> wrote:>
>
> On Aug 11, 10:54 am, Stefan Schulte <stefan.schu...@taunusstein.net>
> wrote:
>> On Thu, Aug 11, 2011 at 08:30:37AM -0700, Aaron Grewell wrote:
>> > It''s fine, just make sure class2 requires class1. 
That''s what requires
are>> > for.
>>
>> Unfortunately it still doesnt worked. Changed class2 to
>>
>>     class mod2::class2 {
>>       file { $mod1::class1::message:
>>         ensure  => file,
>>         require => Class[''mod1::class1''],
>>       }
>>     }
>>
>> Manifest is still
>>
>>     class { ''mod2::class2'': }
>>     class { ''mod1::class1'': message =>
''Hallo Welt''}
>>
>> What I get is
>>
>> warning: Scope(Class[Mod2::Class2]): Could not look up qualified
>> variable ''mod1::class1::message''; class mod1::class1
has not been
>> evaluated at /tmp/modules/mod2/manifests/class2.pp:2
>
>
> I must say I''m not surprised that one didn''t work.
Indeed, I would
> have been surprised if it had. The require is inside a scope defined
> by the variable in question, and that scope can''t be defined in
the
> first place.
>
> I think I know what''s going on. Basically,
''require'' and its friends
> are the the wrong tool for the job: they establish order relationships
> for determining the order in which resources are *applied* by the
> agent, but they not necessarily the order in which resources are
> evaluated during catalog compilation by the master.
>
> Were class1 not parameterized, I would recommend that class2 simply
> ''include'' it, and I am confident that would make it all
good. But you
> cannot do that with a parameterized class (as far as I am aware), so I
> think that leaves you up a creek.
>
>
> John
> Parameterized Classes -- Finding new ways to break your manifests
> since 2010!
>
> --
> You received this message because you are subscribed to the Google Groups
"Puppet Users" group.> To post to this group, send email to puppet-users@googlegroups.com.
> To unsubscribe from this group, send email to
puppet-users+unsubscribe@googlegroups.com.> For more options, visit this group at
http://groups.google.com/group/puppet-users?hl=en.>
-- 
You received this message because you are subscribed to the Google Groups
"Puppet Users" group.
To post to this group, send email to puppet-users@googlegroups.com.
To unsubscribe from this group, send email to
puppet-users+unsubscribe@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/puppet-users?hl=en.

Puppet users - Aug 2011 - Is accessing vars from different class safe?

[Puppet Users] Is accessing vars from different class safe?

[Puppet Users] Re: Is accessing vars from different class safe?

Re: [Puppet Users] Is accessing vars from different class safe?

Re: [Puppet Users] Is accessing vars from different class safe?

Re: [Puppet Users] Is accessing vars from different class safe?

Re: [Puppet Users] Is accessing vars from different class safe?

Re: [Puppet Users] Is accessing vars from different class safe?

[Puppet Users] Re: Is accessing vars from different class safe?

Re: [Puppet Users] Re: Is accessing vars from different class safe?