On Monday, July 15, 2013 11:25:50 AM UTC-5, Brano Zarnovican wrote:
>
> Hi,
>
> I have the following code snippet
>
> node default {
> # $var_a .. is undefined
> $var_b = hiera("var_b", undef)
> $var_c = undef
>
> file { "/var/tmp/foo.txt": content => inline_template("
>
> <% if @var_a %>
> var_b = <%= @var_a %>
> <% else %>
> <% info(\"var_a is undefined\") %>
> <% end -%>
>
> <% if @var_b %>
> var_b = <%= @var_b %>
> <% else %>
> <% info(\"var_b is undefined\") %>
> <% end -%>
>
> <% if @var_c %>
> var_c = <%= @var_c %>
> <% else %>
> <% info(\"var_c is undefined\") %>
> <% end -%>
>
> "
> ), }
> }
>
> Applying it, will generate these two info messages.
>
> Info: template[inline]: var_a is undefined
> Info: template[inline]: var_c is undefined
> var_b =
>
> What I would like puppet to do is to fail if template is referencing a
> variable which is not defined, without having to wrap it with
> if-else-fail()-end.
>
> Another strange thing I've noticed that "undef" behaves differently if it
> is a default value for hiera lookup (see var_b vs var_c).
>
> Actually, my code looks more like..
>
> $var_a = hiera("var_a")
> $var_b = hiera("var_b")
> $var_c = hiera("var_c")
> file {"..": content => template(hiera("tmpl_name")) }
>
> That will fail if any variable a,b,c is undefined in hiera, no matter if
> it is used in template or not. I can rewrite it to
>
> $var_a = hiera("var_a", undef)
> $var_b = hiera("var_b", undef)
> $var_c = hiera("var_c", undef)
> file {"..": content => template(hiera("tmpl_name")) }
>
> This will not fail even if variable used by the template is undefined. The
> value is quietly replaced by empty string.
>
> In other words, I would like to delay the failure from hiera() lookup to
> the time when it is actually used in template. Can it be done without
> explicitly testing it with "if" inside template ?
>
> Thanks,
>
> BranoZ
>
> PS: we are (or soon be) on puppet 3.2.
>
>
You have a couple of separate issues here, but first a little background to
make sure we're on the same page: templates are evaluated by the master,
not by agents, so the only form of failure a template can exhibit is to
interrupt catalog compilation with a synthetic parse error. It cannot
cause application of the associated resource to fail on the agent.
With that said, a template can call Puppet function via the 'scope' object
available to it. In particular, if you want a template evaluation to fail
as I describe, then it can invoke the fail() function:
<% scope.function_fail('variable foo is not set') %>
Now, as a separate matter, you are correct that hiera will translate the
default value 'undef' to an empty string. It will never return an undef
value (I'm not sure that even makes sense). A common approach is to
instead choose a default value that you are confident will not appear as a
valid value in your data. One conventional choice is 'NOTSET'. Your code
then tests for that special value instead of (or in addition to) testing
whether the variable is defined.
John
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