Removing intermediate variables in calculation

[Amos Shapira]

Hello,

I have a small Puppet 2.7 module to configure Sonatype Nexus Professional. The module takes, among other things, a baseurl in the form of "http://example.com/path" and I'd like it to extract the "/path" from that variable into a separate variable IF an optional "path" variable haven't been supplied.

Here is an extract:
class nexus::config(
...
  $baseurl,
  $webapp_context_path = '/'
) {
  if ($webapp_context_path != '')
  {
    $int_webapp_context_path = $webapp_context_path
    notify{"using webapp_context_path \"${webapp_context_path}\"":}
  }
  else
  {
    $extracted_url_path = regsubst($baseurl, '^https?://[^/]+(/.*)', '\1')
    if ($extracted_url_path)
    {
      $int_webapp_context_path = $extracted_url_path
    }
    else
    {
      # in case we were given a $baseurl without the tailing "/"
      $int_webapp_context_path = '/'
    }
    notify{"extracted int_webapp_context_path \"${int_webapp_context_path}\" from url \"${baseurl}\"": }
  }

  # use $int_webapp_context_path in the .erb template file

My question - this use of $int_webapp_context_path and $extracted_url_path looks a bit shabby. But I didn't find a way to use conditional assignments to remove these intermediate variables and either:
1. Assign the value I want to $webapp_context_path if it's not set yet.
2. Or at least get rid of the $extracted_url_path

Is there a nicer way to achieve the above?

Thanks.

[Guzman Braso]

I'm in no way a puppet guru.... but rewritting it didnt work? from a logic point of view this should work:

class ....

  $baseurl,

  $webapp_context_path = ''

) {

  if ($webapp_context_path == '') {   

    # Try to get value from baseurl

    $webapp_context_path = regsubst($baseurl, '^https?://[^/]+(/.*)', '\1')

    if ($webapp_context_path == '') {

      #Set default

      $webapp_context_path = '/'

    }

 }  

 notify{"rewritted webapp_context_path='${webapp_context_path}' from url='${baseurl}'": }
}

But as I said I'm fairly new with puppet, did not tried above code.

On Mon, Oct 1, 2012 at 10:28 PM, Amos Shapira <amos.s...@gmail.com> wrote:

Hello,

I have a small Puppet 2.7 module to configure Sonatype Nexus Professional. The module takes, among other things, a baseurl in the form of "http://example.com/path" and I'd like it to extract the "/path" from that variable into a separate variable IF an optional "path" variable haven't been supplied.

Here is an extract:

class nexus::config(
...
  $baseurl,

  $webapp_context_path = ''
) {
  if ($webapp_context_path == '')
  {
    $webapp_context_path = regsubst($baseurl, '^https?://[^/]+(/.*)', '\1')

   

   $webapp_context_path = regsubst($baseurl, '^https?://[^/]+(/.*)', '\1')

    if ($extracted_url_path)
    {
      $int_webapp_context_path = $extracted_url_path
    }
    else
    {
      # in case we were given a $baseurl without the tailing "/"
      $int_webapp_context_path = '/'
    }
    notify{"extracted int_webapp_context_path \"${int_webapp_context_path}\" from url \"${baseurl}\"": }
  }

  # use $int_webapp_context_path in the .erb template file

My question - this use of $int_webapp_context_path and $extracted_url_path looks a bit shabby. But I didn't find a way to use conditional assignments to remove these intermediate variables and either:
1. Assign the value I want to $webapp_context_path if it's not set yet.
2. Or at least get rid of the $extracted_url_path

Is there a nicer way to achieve the above?

Thanks.

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[jcbollinger]

On Tuesday, October 2, 2012 10:10:13 AM UTC-5, Guzmán Brasó wrote:

I'm in no way a puppet guru.... but rewritting it didnt work? from a logic point of view this should work:

class ....

  $baseurl,

  $webapp_context_path = ''

) {

  if ($webapp_context_path == '') {   

    # Try to get value from baseurl

    $webapp_context_path = regsubst($baseurl, '^https?://[^/]+(/.*)', '\1')

    if ($webapp_context_path == '') {

      #Set default

      $webapp_context_path = '/'

    }

 }  

 notify{"rewritted webapp_context_path='${webapp_context_path}' from url='${baseurl}'": }
}

No, that won't work, because Puppet variables, including class and definition parameters, can be assigned a value at most once.  There are good reasons for that, but they're not really relevant to the present question.
 
Anyway, for that very reason, constructs involving internal variables such as $int_webapp_context_path are fairly standard practice in Puppet.  Among the alternatives could be to redesign your class parameterization or to drop the adaptive behavior.  Or you could write a custom function implementing the logic for context path selection, or you could put it into your template instead of your class.

(Note, by the way, that because you assign a default value of '/' to $webapp_context_path in your parameter list, in the class body that parameter will be observed to have an empty value only if such a value is explicitly set when the class is declared.)


John

[Amos Shapira]

Thanks Guzman, as John pointed out that won't work (I think this is because Puppet's language is declarative, even if it resembles procedural language in many ways).

[Amos Shapira]

Thanks John. At least I know there is no way to improve my code.
I prefer to try to keep logic in the .pp files and out of the templates, just to make it easier to find.