external node classifiers

[Stuart Cracraft]

Hi,

I'd like to use ENC::

  http://docs.puppetlabs.com/guides/external_nodes.html

to keep hardwired customizations away from our classes and other files as much as possible

particularly for the node name, but potentially as esoteric as a machine configuration, file

permission, service name, etc - to keep the classes as flexible and general as possible.

My questions:

  + have you done the above?

  + what were your learnings

  + do you have sample puppet_node_classifier's you can share?

  + how to use the definitions from ENC via the pm's puppet.conf's linkage to the ENC

       [main]

       :

       node_terminus = exec

       external_nodes = /usr/local/bin/puppet_node_classifier

       :

My current question is how do you use the ENC definitions within the classes?

Is this adequately described in-depth in the yet-to-be-published Puppet book?

Stuart

[Jason Antman]

Stuart,

Yes, many of us use ENCs, though it seems to be mostly limited to larger
shops; these days many people are moving in the direction of hiera
instead. I've been using various ENCs for the past ~4 years.

There are relatively few good choices for already-written ENCs. (well,
if you just want a simple script, you can write it yourself; most of the
"ENCs" that are available provide a web interface for configuring
everything). The most popular options that I know of are Puppet
Dashboard (aka Console in Puppet Enterprise) and Foreman. The current
version of Dashboard (IMHO) has some serious issues, though PL is
actively working on them and I'm told that big improvements can be
expected. Foreman is good, solid software but does a LOT in terms of
provisioning, DNS and DHCP control, etc. as well as a lot of internal
logic about setting variables and classes, etc. so I feel that it's a
bit much if all you want is a plain-and-simple ENC.

I'm in the process of polishing up my company's internal ENC, and plan
on releasing it on github. It's a python/Django app that supports
multiple inheritance and overrides, class and parameter exclusions, and
has full support for parameterized classes and deep data structures.

That being said, I've also written ENCs in the past that were quite
simple - type in a hostname, check off some boxes for classes and
groups, and you're done.

As to samples - unfortunately, no, I don't... but you just need some
script that prints valid YAML according to the spec. Without knowing
more about how you want it to work, I can't provide much of an example.

"My current question is how do you use the ENC definitions within the
classes?"

Well, most of the ENCs I've used in the past (Puppet Dashboard included)
just return a list of classes to apply to the node, and a list of
parameters. The parameters are passed to puppet as top-scope variables.
So your ENC defines a parameter called, say, httpd_version, and
somewhere in your httpd class, you use $::httpd_version. Of course then
you really need to follow the params.pp pattern to declare a default
value, and validate what the ENC passes in. This pattern really sucks.

Lately, especially since puppet3 came out, I've been using an ENC that
supports parameterized classes. So I don't do anything special in my
classes (in fact much of what I use are modules from the Forge), and I
just tell the enc what classes I want, and the parameters that I want
passed in to them. This allows me to use many of the forge modules
(especially the puppetlabs ones) straight from my ENC.

I'd be happy to provide a bit more advice if you have more specific
questions.

-Jason

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[jcbollinger]

On Tuesday, December 3, 2013 5:50:47 PM UTC-6, Stuart Cracraft wrote:

Hi,

I'd like to use ENC::

  http://docs.puppetlabs.com/guides/external_nodes.html

to keep hardwired customizations away from our classes and other files as much as possible

particularly for the node name, but potentially as esoteric as a machine configuration, file

permission, service name, etc - to keep the classes as flexible and general as possible.

My questions:

  + have you done the above?

I'd like to think that I write flexible, general classes.  That's pretty much orthogonal to use of an ENC, however, and in fact I do not use an ENC.  You are quite right, however, that a big part of making your classes flexible and general is to keep data out of classes -- that is, to externalize your data.

 

  + what were your learnings

  + do you have sample puppet_node_classifier's you can share?

  + how to use the definitions from ENC via the pm's puppet.conf's linkage to the ENC

I don't think I understand the question.  Your puppet.conf specifies the ENC to use.  Each time a node requests a catalog from the master, it runs the specified ENC program, passing the node's identifier as an argument.  The master parses the ENC's YAML output to obtain global variable settings and the names of classes that should be declared for the given node, optionally with associated maps of class parameter values.  These may be supplemented by node declarations appearing in your manifests.

You don't actively "use" definitions from an ENC; rather, the master automatically incorporates the ENC output as a source of declarations about the target node.  ENCs are a non-exclusive alternative to node declarations.

If what you are looking for is simply a way to externalize data used by your classes, then hiera is Puppet's built-in facility supporting that.  Open-source Puppet does not provide a GUI for hiera configuration or hiera data manipulation (I don't know about PE), but the general thrust of your questions leads me to suspect that that may not be important to you.  Hiera supports automatic binding of data to class parameters, but its classic usage mode is via a lookup function in your manifest code:

  $my_special_datum = hiera('special')

.  Thus, you can draw data from hiera without using parameterized classes or in addition to via automated class parameter binding, if you should wish to do so.

 

       [main]

       :

       node_terminus = exec

       external_nodes = /usr/local/bin/puppet_node_classifier

       :

My current question is how do you use the ENC definitions within the classes?

Is this adequately described in-depth in the yet-to-be-published Puppet book?

I can't speak to the content of any unpublished book, but I think the PL docs cover the matter pretty well already: http://docs.puppetlabs.com/guides/external_nodes.html.


John

[Stuart Cracraft]

Chapter 5 at page 119 in the Pro Puppet book of 2011 by Turnbull/McCune

has good explanation and scripts, in Shell, Perl, Ruby.