On May 2, 3:14 pm, Ryan Bowlby <rbowlb...@gmail.com> wrote:
> Hi All,
>
> I recently added the puppet-concat module in order to implement the
> example motd use case. Now our motd includes a list of modules being
> used on the server, which is awesome.
>
> All the modules define an motd::register so they expect that the motd
> module was included. When a node does not include the module all those
> dependent modules fail. I would like to have each module first check
> to see if the motd class has been included.
>
> Current example:
>
> class pulp (..
> .....
>
> # list this module/class in motd
> os::motd::register {"pulp": }
>
> }
> Future example:
>
> class pulp (..
> .....
> if defined(os::motd) {
> # list this module/class in motd
> os::motd::register {"pulp": }
> }
>
> }
You are confusing me with your terminology. An entity referred to in
a Puppet manifest as 'os::motd' is either a class or a defined type in
module 'os', not a module itself. You can "include" or "declare" a
class, but not a module. You can "instantiate" or sometimes "declare
[an instance of]" a defined type, or some people "call" one. Your
manifests cannot directly refer to a module at all, only to its
contents.
I'm not familiar with the motd module, but os::motd::register must be
a defined type. It should be the responsibility of the definition to
include any classes it depends on. It can and should do so unless one
or more of those classes is parameterized, so that your own classes
that use it Just Work. If the definition needs a parameterized class
to have been declared, however, then it thereby leaves you hanging.
> The question is whether this is the right way to go about it? Does the
> define wait for all class declarations before checking (does order
> matter)?
No and no (and yes). Parse-order dependency is a prime reason why
such useage of the 'defined' function is poor practice. There has
even been some discussion of deprecating it.
If 'os::motd' is an unparameterized class, then your best options are:
1) put "include 'os::motd'" at the begining of the body of
os::motd::register, OR
2) put "include 'os::motd'" at the begining of every class that
instantiates os::motd::register, OR
3) put "include 'os::motd'" at the begining of every node definition
(or make your ENC output that class first in its class list)
If 'os::motd' is a parameterized class then your best bet is to adjust
your node declarations / ENC so that os::motd is declared first for
every node.
John
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