Puppet

A request for this feature recently came up [1] on the puppet-users mailing list.

[1] Definitions in External Nodes

This is a blocker for our puppet roll out. Do you know in which release this will be done? Is there a way we could help?

We don’t have a clear plan for directly adding resources from an ENC, so working on defining that plan would be a huge help :)

It’s a reasonably large behavior change to make an ENC now support adding resources directly (including their parameters) rather than just saying what classes should be added.

Note the workaround is to pass node parameters for use with classes that use those parameters to instantiate the resources. It’s at least one too many abstraction layers… but does work :(

I thought about this when taking a shower this morning. From a sysadmin point of view, it would be the easiest if we could provide a yaml which looks like:

classes:
  common:
  apt:
resources:
  - "add local repo":
    type: "apt::repo"
    ensure: present
    content: "deb localrepo.magpie.lan/ubuntu lucid vendor"
  - "touch restart.txt":
    type: "exec"
    user: "root"
    command: "touch /var/www/rails/tmp/restart.txt"
    unless: "/var/www/rails/tmp/restart.txt"
    require:
      - file: "/var/www/"
      - file: "/var/www/rails"

This would evaluate to something like this:

irb> pp YAML.load(File.open("/tmp/l"))
{"resources"=>
  [{"type"=>"apt::repo",
    "content"=>"deb localrepo.magpie.lan/ubuntu lucid vendor",
    "ensure"=>"present",
    "add local repo"=>nil},
   {"command"=>"touch /var/www/rails/tmp/restart.txt",
    "type"=>"exec",
    "require"=>[{"file"=>"/var/www/"}, {"file"=>"/var/www/rails"}],
    "unless"=>"/var/www/rails/tmp/restart.txt",
    "user"=>"root",
    "touch restart.txt"=>nil}],
 "classes"=>{"common"=>nil, "apt"=>nil}}

Is this something you meant? Or did you mean something else by “helping to define a plan”? :)

No, that’s a great start. Would you like to take this to the puppet-users list for comment?

Although it’s possible to put naked resources into site.pp at the top level, we’ve generally been moving away from that as a community towards classes/modules for everything, and this does modify that somewhat.

To be clear, I’m not opposed to this, it fits reasonably well, I just haven’t convinced myself that we’ve considered all the aspects :)

Nigel Kersten wrote:

Although it’s possible to put naked resources into site.pp at the top level, we’ve generally been moving away from that as a community towards classes/modules for everything, and this does modify that somewhat.

I’m aware of this direction, but I’m not convinced it reasonably covered all use-cases. Maybe it does and I haven’t been thinking about it the right way but there are some cases where it feels like parameterized classes are awkward.

In our environment every server we deploy in Puppet has multiple network interfaces (at least two, but variable in type and quantity) and we use Puppet to deploy the network interfaces configurations. In this case, on RHEL so /etc/sysconfig/network-scripts/ifcfg-ethX style files. In each node stanza we use a definition to instantiate these network configs, something like:

intf::eth { 'eth0': ip => '192.168.1.10/24' }
intf::eth { 'eth1': ip => '10.2.2.2/24' }

In this case we could probably implement something via a hash, but sometimes the definitions get quite a bit more complex, with entries for 802.1q tagged VLAN interfaces, bonding interfaces, etc. Under the hood the defines make sure the files get created from templates as needed and according to our best practices.

We use similar definitions for iproute2 routes and rules.

Given that those resources are variable in type and quantity per-node it seems like definitions at the node level is the most elegant way of handling it.

The lack of definition/resource support in ENCs are preventing our use of an ENC and the changed scoping rules in 2.7 require us to use an ENC to implement things we have working in 2.6. Right now we are stuck between these two problems.

Cool. I created now a thread called “Definitions in a external node classifier”. It’s waiting to be approved by a moderator.