On Tuesday, January 21, 2014 11:49:15 PM UTC-6, bluethundr wrote:
>
> Hey all,
>
> Sorry but I forgot to include a key piece of information in that last
> email.
>
> In the ssh class I have defined in the modules init.pp I had this
> definition:
>
> class ssh {
> include ssh::install, ssh::config, ssh::service, ssh::params
> }
>
>
> But then I read on into the book a little more and found out about the
> require function. So I changed the ssh class definition to this:
>
> class ssh {
> require ssh::params
> include ssh::install, ssh::config, ssh::service
> }
>
> And that solved the problem! Still curious as to why the original class
> definition failed to work with the include function specifying ssh::params.
> So if anyone out there cares to enlighten on that issue, that'd be great.
>
> Glad however that I was able to get this working.
>
You have a misapprehension. It was not changing from 'include' to
'require' that made the difference. It was putting the 'require' statement
before the 'include's in your manifest. Provided you leave it positioned
where it now is, you could change the 'require' back to an 'include'
without breaking anything (and you should do).
The underlying problem is that class ssh::config depends on class
ssh::params, but does not explicitly tell Puppet so. Generally speaking,
if class A uses class variables of class B, then class A should 'include'
class B at the top of its body. That expresses the compile-time dependency
in a way that Puppet understands. If it does not express the dependency to
Puppet, then whether class B is evaluated first is unspecified.
The above comes with some qualifications and provisos, however, among them:
1. If you use parameterized-style class declarations in your manifests
then other declarations of the same classes serve documentary purposes
only. Compilation will fail if a parameterized-style declaration of class
P (class { 'p': [parameters ...] }) is encountered when class P has
already been declared, and no additional declaration is needed one has
already been evaluated.
2. If class A has both compile-time and order-of-application
dependencies on class B, then both dependencies can be expressed together
via a 'require' statement. For code clarity, you should avoid 'require'
except in such cases.
I have long maintained that (1) is an outstanding reason to avoid
parameterized class declaration syntax. In Puppet 3, you can rely instead
on automated data binding via hiera, at least where you "must" use
parameterized classes at all. (There is never an absolute need to do so,
but it may be convenient, especially when third-party modules are
involved.) With some care, parameterized-style declarations can safely be
used within a module to declare internal classes of that same module, but
that's about it.
John
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