Puppet users - Feb 2011 - Pattern for modifying a "master node" when a "slave node" is configured with puppet

Hi there!  I''m somewhat new to puppet, and just got back from
PuppetLabs
training in Boston last week.  One pattern that i didn''t consider until
after the class is how to update a master node when a slave node is brought
online..

I have  anode called dispatcher and several slaves called slave1..2..3,etc.

When slave3 is puppetized (ie built via puppet), several files need to be
modified on the dispatcher machine to let it know that slave3 now exists.

I can see having a build script that runs on puppet master and keeps those
files in /etc/puppet/files/dispatcher/* updated, but that seems more like
the old way I''ve done things.

Is there a "puppet" way to do something like this.

Thanks!

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On Mon, Feb 07, 2011 at 12:12:45PM -0500, Joe Esposito
wrote:
> Hi there!  I''m somewhat new to puppet, and just got back from
PuppetLabs
> training in Boston last week.  One pattern that i didn''t consider
until
> after the class is how to update a master node when a slave node is brought
> online..
> 
> I have  anode called dispatcher and several slaves called slave1..2..3,etc.
> 
> When slave3 is puppetized (ie built via puppet), several files need to be
> modified on the dispatcher machine to let it know that slave3 now exists.
> 
> I can see having a build script that runs on puppet master and keeps those
> files in /etc/puppet/files/dispatcher/* updated, but that seems more like
> the old way I''ve done things.
> 
> Is there a "puppet" way to do something like this.
> 
> Thanks!
> 
Yes, there is a way:
http://docs.puppetlabs.com/guides/exported_resources.html

In short: You have to enable storeconfigs on the master. Then you can do
something like (not tested, maybe syntax errors)

  # In your slaves manifest
  @@file { "/master/${fqdn}.conf":
    content => "I am $fqdn to your service\n",
    ensure  => file,
    tag     => "dispatcher_slave",
  }

When the you run puppet on the slave now, the slave will not install
that file on its own system but the file resource (with resolved facts like fqdn
will be exported to the master which will now store the resource in a database
(sqlite, MySQL, whatever you configured).

You can install that file on any host now.

  # In your dispatcher''s manifest
  File <<| tag == "dispatcher_slave" |>>

This will realize every exported file that is tagged with
"dispatcher_slave". So on your dispatcher you will now have a file
called /master/slave1.conf with »I am slave1 to your service«.

Setting up stored config is described here:
http://projects.puppetlabs.com/projects/1/wiki/Using_Stored_Configuration

Hope that helps.

-Stefan