Puppet users - May 2007 - hosts.equiv management?

My first public-facing deployment of Puppet is likely to be on some 
parallel computing nodes we have here. One of our fluid dynamics 
packages expects to be able to rsh from one master node to other slave 
nodes in the same batch queue. I think I''ve made some good class 
definitions up to this last point, where code duplication rears its head.

Example of the problem:

class ch405-host inherits dual-boot-cluster-host {
     $myqueue = ''ch405''
     file { "/etc/hosts.equiv":
         source  => 
"puppet://$pserver/files/apps/rsh-server/hosts.equiv.$myqueue",
         owner   => root,
         group   => root,
         mode    => 644,
         require => Package[rsh-server],
     }
}

class ch406-host inherits dual-boot-cluster-host {
     $myqueue = ''ch406''
     file { "/etc/hosts.equiv":
         source  => 
"puppet://$pserver/files/apps/rsh-server/hosts.equiv.$myqueue",
         owner   => root,
         group   => root,
         mode    => 644,
         require => Package[rsh-server],
     }
}

node ch405a, ch405b, ch405c, ch405d, ch405e, ch405f, ch405g, ch405h, 
ch405i, ch405j, ch405k, ch405l, ch405m, ch405n {
   include ch405-host
}

node ch406a, ch406b, ch406c, ch406d, ch406e, ch406f, ch406g, ch406h, 
ch406i, ch406j, ch406k, ch406l, ch406m, ch406n {
   include ch406-host
}

So the end result is that all ch405* nodes get the same hosts.equiv 
file, and all ch406* nodes get a different hosts.equiv file. Where 
should I look to get rid of the duplicated code?

-- 
Mike Renfro  / R&D Engineer, Center for Manufacturing Research,
931 372-3601 / Tennessee Technological University -- renfro@tntech.edu

On May 25, 2007, at 2:59 PM, Mike Renfro wrote:
>
> So the end result is that all ch405* nodes get the same hosts.equiv
> file, and all ch406* nodes get a different hosts.equiv file. Where
> should I look to get rid of the duplicated code?
The main strategy is to create a single class with the file copy in  
it (possibly put it into the ''rsh'' class or something), then
find a
way to select the best queue outside that class.

There are a couple of strategies for this.  One way is to set tags  
and use those:

node ch406, .... {
   tag(ch406)
}

Then test the tags:

class rsh {
   if tagged(ch406) {
     $queue = "..."
   } else {
   ...
   }
}

As mentioned, though, tags are file-order-dependent, which makes them  
not a very good solution, and really, they kind of obscure what  
you''re doing here, and they don''t maximize configuration
normalization.

I''d recommend writing a custom function that can turn the hostname  
into a queue, and then use the default node.  You can use a one-liner  
in generate(), instead:

$name = ch406a
$site = generate("/usr/bin/ruby", "-e", "print
''$name''.sub(/[a-z]*$/,
'''')")
notify { "site is $site": }
==>
notice: site is ch406

Note I don''t necessarily recommend these one-liners, but you get the  
idea.  A server-side function, or a stand-alone script used with  
generate(), is a better option, if for no other reason than it''s  
clear what you''re doing and you don''t have to worry about
quoting.

Do this in the default node, then include the rsh class:

node default {
   $queue = generate(...) # use $hostname
   include rsh
}

Then the rsh class just picks the file appropriate for a given queue.

This still isn''t the best solution, since there is still the  
possibility of ordering quirks -- the rsh class must be included by  
the same scope that sets $queue (we''re working on this) -- but it  
should get you there.

  --
  DOS is the _only_ operating system -- and I''m using that term
  loosely -- which [exhibits this behavior].
             --Aeleen Frisch, "Essential System Administration"
  ---------------------------------------------------------------------
  Luke Kanies | http://reductivelabs.com | http://madstop.com