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Brano Zarnovican

2013-Jul-15 16:25 UTC

[Puppet Users] template - need to fail if referencing undefined var

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.

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jcbollinger

2013-Jul-17 15:29 UTC

head link

[Puppet Users] Re: template - need to fail if referencing undefined var

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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Spencer Krum

2013-Oct-16 17:48 UTC

head link

[Puppet Users] Re: template - need to fail if referencing undefined var

I''ve developed the following pattern. Please don''t hate.

[nibz@pdxudev01 sandbox]$ cat testpuppetfailtemplate.sh 

$bar = ''lies''

$derp=inline_template("<%= @bar ||
scope.function_fail([''die'']) %>")
notify { $derp: }

Which produces:

[nibz@pdxudev01 sandbox]$ puppet apply testpuppetfailtemplate.sh 
Notice: lies
Notice: /Stage[main]//Notify[lies]/message: defined ''message''
as ''lies''
Notice: Finished catalog run in 0.09 seconds

Then commenting out $bar

[nibz@pdxudev01 sandbox]$ puppet apply testpuppetfailtemplate.sh 
Error: Failed to parse inline template: die at 
/home/nibz/sandbox/testpuppetfailtemplate.sh:4 on node 
pdxudev01.devtst.go2uti.com
Error: Failed to parse inline template: die at 
/home/nibz/sandbox/testpuppetfailtemplate.sh:4 on node 
pdxudev01.devtst.go2uti.com

:)



On Wednesday, July 17, 2013 8:29:07 AM UTC-7, jcbollinger
wrote:>
>
>
> 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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Nan Liu

2013-Oct-16 18:52 UTC

head link

Re: [Puppet Users] Re: template - need to fail if referencing undefined var

This is essentially the behavior of stdlib pick function.

$required_var = pick(hiera("var_a"), hiera("var_b"))

Which could be improved to allow a custom error message:
https://github.com/puppetlabs/puppetlabs-stdlib/blob/master/lib/puppet/parser/functions/pick.rb#L24

Nan


On Wed, Oct 16, 2013 at 10:48 AM, Spencer Krum
<krum.spencer@gmail.com>wrote:
> I''ve developed the following pattern. Please don''t hate.
>
> [nibz@pdxudev01 sandbox]$ cat testpuppetfailtemplate.sh
>
> $bar = ''lies''
>
> $derp=inline_template("<%= @bar ||
scope.function_fail([''die'']) %>")
> notify { $derp: }
>
> Which produces:
>
> [nibz@pdxudev01 sandbox]$ puppet apply testpuppetfailtemplate.sh
> Notice: lies
> Notice: /Stage[main]//Notify[lies]/message: defined
''message'' as ''lies''
> Notice: Finished catalog run in 0.09 seconds
>
> Then commenting out $bar
>
> [nibz@pdxudev01 sandbox]$ puppet apply testpuppetfailtemplate.sh
> Error: Failed to parse inline template: die at
> /home/nibz/sandbox/testpuppetfailtemplate.sh:4 on node
> pdxudev01.devtst.go2uti.com
> Error: Failed to parse inline template: die at
> /home/nibz/sandbox/testpuppetfailtemplate.sh:4 on node
> pdxudev01.devtst.go2uti.com
>
> :)
>
>
>
> On Wednesday, July 17, 2013 8:29:07 AM UTC-7, jcbollinger wrote:
>>
>>
>>
>> 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
>>
>>  --
> You received this message because you are subscribed to the Google Groups
> "Puppet Users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to puppet-users+unsubscribe@googlegroups.com.
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> Visit this group at http://groups.google.com/group/puppet-users.
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>
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Puppet users - Jul 2013 - template - need to fail if referencing undefined var

[Puppet Users] template - need to fail if referencing undefined var

[Puppet Users] Re: template - need to fail if referencing undefined var

[Puppet Users] Re: template - need to fail if referencing undefined var

Re: [Puppet Users] Re: template - need to fail if referencing undefined var