Puppet users - Mar 2012 - Hash iteration order in a template not consistent

Hi,

I did some basic googling, but didn''t find an answer yet. I am sorry if
this is a FAQ.

In a manifest for creating an Apache config file, I define a hash like this:

    $aliases = {
        ''/foo/''     => ''/home/foo/www/'',
        ''/bar/''     => ''/home/bar/www/'',
        ''/baz/''     => ''/home/baz/www//''
    }

Then, in a template, I have:

    <% aliases.each_pair do |key, val| -%>
        Alias <%= key %>     <%= val %>
    <% end -%>

The result is mostly what I expect, but every once in a while, the order
in which the Aliases are generated from the ''each_pair'' loop
changes,
resulting in a different file.

The Ruby docs state that "hashes enumerate their values in the order that
the corresponding keys were inserted.", but is that not true for Puppet
hashes?

I did stumble across this post:

http://serverfault.com/questions/368784/puppet-and-templates-how-to-loop-sequently-and-not-randomly

which suggests to do something like

    <% aliases.sort_by {|key, value| key}.each_pair do |key, val| -%>
    <% end -%>

Will it work? Is that a proper solution?

Thanks!
Martijn Grendelman

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----- Original Message -----
> From: "Martijn Grendelman" <martijn@iphion.nl>
<snip>
>
http://serverfault.com/questions/368784/puppet-and-templates-how-to-loop-sequently-and-not-randomly
> 
> which suggests to do something like
> 
>     <% aliases.sort_by {|key, value| key}.each_pair do |key, val| -%>
>     <% end -%>
> 
> Will it work? Is that a proper solution?
ruby hashes are not stored in predictable order so this will happen, the
proposed
solution should work.

But as always the best is just to test it and see how it goes, it wont bite :)

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Hi, I did it something like that:

<% aliases.sort.each do |alias| -%>
   Alias <%= alias.first %>     <%= alias.last %>
<% end -%>

Regards.
> Hi,
>
> I did some basic googling, but didn''t find an answer yet. I am
sorry if
> this is a FAQ.
>
> In a manifest for creating an Apache config file, I define a hash like
this:
>
>      $aliases = {
>          ''/foo/''     => 
''/home/foo/www/'',
>          ''/bar/''     => 
''/home/bar/www/'',
>          ''/baz/''     => 
''/home/baz/www//''
>      }
>
> Then, in a template, I have:
>
>      <% aliases.each_pair do |key, val| -%>
>          Alias<%= key %>      <%= val %>
>      <% end -%>
>
> The result is mostly what I expect, but every once in a while, the order
> in which the Aliases are generated from the ''each_pair''
loop changes,
> resulting in a different file.
>
> The Ruby docs state that "hashes enumerate their values in the order
that
> the corresponding keys were inserted.", but is that not true for
Puppet
> hashes?
>
> I did stumble across this post:
>
>
http://serverfault.com/questions/368784/puppet-and-templates-how-to-loop-sequently-and-not-randomly
>
> which suggests to do something like
>
>      <% aliases.sort_by {|key, value| key}.each_pair do |key, val|
-%>
>      <% end -%>
>
> Will it work? Is that a proper solution?
>
> Thanks!
> Martijn Grendelman
>
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On 28-03-12 14:39, R.I.Pienaar wrote:
> 
> 
> ----- Original Message -----
>> From: "Martijn Grendelman" <martijn@iphion.nl>
> 
> <snip>
> 
>>
http://serverfault.com/questions/368784/puppet-and-templates-how-to-loop-sequently-and-not-randomly
>>
>> which suggests to do something like
>>
>>     <% aliases.sort_by {|key, value| key}.each_pair do |key, val|
-%>
>>     <% end -%>
>>
>> Will it work? Is that a proper solution?
> 
> ruby hashes are not stored in predictable order so this will happen, the
proposed
> solution should work.
> 
> But as always the best is just to test it and see how it goes, it wont bite
:)
> 

<% aliases.sort_by {|key, value| key}.each do |key, val| -%>

seems to do the trick. ''each_pair'' doesn''t work here,
because the sort_by
returns an array. Again, I learned something :-)

Thanks,
Martijn.

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On Thu, 29 Mar 2012 10:06:01 +0200
Martijn Grendelman <martijn@iphion.nl> wrote:

[...]
> >
> > ruby hashes are not stored in predictable order so this will
> > happen, the proposed solution should work.
> > 
> > But as always the best is just to test it and see how it goes, it
> > wont bite :)
> 
> <% aliases.sort_by {|key, value| key}.each do |key, val| -%>
> 
> seems to do the trick. ''each_pair'' doesn''t work
here, because the
> sort_by returns an array. Again, I learned something :-)
...and what about those of us which want the hash entries to appear in
the exact same order they are present in the puppet manifest? From what
I''ve seen, it was working that way up to 2.6 included, and only gets
"randomized" with puppet 2.7.

I''ve been doing things like this for a while now :

  mm_cfg_settings => {
    ''ALLOW_SITE_ADMIN_COOKIES'' => "Yes",
    ''PUBLIC_ARCHIVE_URL'' =>
"''https://%(hostname)s/pipermail/%(listname)s''",
    ''MTA'' => "''Postfix''",
    ''POSTFIX_STYLE_VIRTUAL_DOMAINS'' =>
"''False''",
    ''DEFAULT_SUBJECT_PREFIX'' =>
"''''",
    ''DEFAULT_REPLY_GOES_TO_LIST'' => "1",
  },

  <% mm_cfg_settings.each do |key,value| -%>
  <%= key %> = <%= value %>
  <% end -%>

In this particular example, order isn''t critical other than for
readability, but I have some others where items must be in the same
order as they appear in the manifest''s hash or things will break.

Is there a way to keep using hashes if the order from the manifest must
be kept in a file generated from the template?

Matthias

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