Fixing the mcollective deployment story


Getting started with MCollective has always been an adventure, you have to learn a ton of new stuff like Middleware etc. And once you get that going the docs tend to present you with a vast array of options and choices including such arcane topics like which security plugin to use while the security model chosen is entirely unique to mcollective. To get a true feeling for the horror see the official deployment guide.

This is not really a pleasant experience and probably results in many insecure or half build deployments out there – and most people just not bothering. This is of course entirely my fault, too many options with bad defaults chosen is to blame.

I saw the graph of the learning curve of Eve Online and immediately always think of mcollective πŸ™‚ Hint: mcollective is not the WoW of orchestration tools.

I am in the process of moving my machines to Puppet 4 and the old deployment methods for MCollective just did not work, everything is falling apart under the neglect the project has been experiencing. You can’t even install any plugin packages on Debian as they will nuke your entire Puppet install etc.

So I figured why not take a stab at rethinking this whole thing and see what I can do, today I’ll present the outcome of that – a new Beta distribution of MCollective tailored to the Puppet 4 AIO packaging that’s very easy to get going securely.


My main goals with these plugins were that they share as much security infrastructure with Puppet as possible. This means we get a understandable model and do not need to mess around with custom CAs and certs and so forth. Focussing on AIO Puppet means I can have sane defaults that works for everyone out of the box with very limited config. The deployment guide should be a single short page.

For a new user who has never used MCollective and now need certificates there should be no need to write a crazy ~/.mcollective file and configure a ton of SSL stuff, they should only need to do:

$ mco choria request_cert

This will make a CSR, submit it to the PuppetCA and wait for it to be signed like Puppet Agent. Once signed they can immediately start using MCollective. No config needed. No certs to distribute. Secure by default. Works with the full AAA stack by default.

Sites may wish to have tighter than default security around what actions can be made, and deploying these policies should be trivial.

Introducing Choria

Choria is a suite of plugins developed specifically with the Puppet AIO user in mind. It rewards using Puppet as designed with defaults and can yield a near zero configuration setup. It combines with a new mcollective module used to configure AIO based MCollective.

The deployment guide for a Choria based MCollective is a single short page. The result is:

  • A Security Plugin that uses the Puppet CA
  • A connector for NATS
  • A discovery cache that queries PuppetDB using the new PQL language
  • A open source Application Orchestrator for the new Puppet Multi Node Application stuff (naming is apparently still hard)
  • Puppet Agent, Package Agent, Service Agent, File Manager Agent all setup and ready to use
  • SSL and TLS used everywhere, any packet that leaves a node is secure. This cannot be turned off
  • A new packager that produce Puppet Modules for your agents etc and supports every OS AIO Puppet does
  • The full Authentication, Authorization and Auditing stack set up out of the box, with default secure settings
  • Deployment scenarios works by default, extensive support for SRV records and light weight manual configuration for those with custom needs

It’s easy to configure using the new lookup system and gives you a full, secure, usable, mcollective out of the box with minimal choices to make.

You can read how to deploy it at it’s deployment guide.


This is really a Beta release at the moment, I’m looking for testers and feedback. I am particularly interested in feedback on NATS and the basic deployment model, in future I might give the current connectors a same treatment with chosen defaults etc.

The internals of the security plugin is quite interesting, it proposes a new internal message structure for MCollective which should be much easier to support in other languages and is more formalised – to be clear these messages always existed, they were just a bit adhoc.

Additionally it’s the first quality security plugin that has specific support for building a quality web stack compatible MCollective REST server that’s AAA compatible and would even allow centralised RBAC and signature authority.

Interacting with the Puppet CA from Ruby


I recently ran into a known bug with the puppet certificate generate command that made it useless to me for creating user certificates.

So I had to do the CSR dance from Ruby myself to work around it, it’s quite simple actually but as with all things in OpenSSL it’s weird and wonderful.

Since the Puppet Agent is written in Ruby and it can do this it means there’s a HTTP API somewhere, these are documented reasonably well – see /puppet-ca/v1/certificate_request/ and /puppet-ca/v1/certificate/. Not covered is how to make the CSRs and such.

First I have a little helper to make the HTTP client:

def ca_path; "/home/rip/.puppetlabs/etc/puppet/ssl/certs/ca.pem";end
def cert_path; "/home/rip/.puppetlabs/etc/puppet/ssl/certs/rip.pem";end
def key_path; "/home/rip/.puppetlabs/etc/puppet/ssl/private_keys/rip.pem";end
def csr_path; "/home/rip/.puppetlabs/etc/puppet/ssl/certificate_requests/rip.pem";end
def has_cert?; File.exist?(cert_path);end
def has_ca?; File.exist?(ca_path);end
def already_requested?;!has_cert? && File.exist?(key_path);end
def http
  http = Net::HTTP.new(@ca, 8140)
  http.use_ssl = true
  if has_ca?
    http.ca_file = ca_path
    http.verify_mode = OpenSSL::SSL::VERIFY_PEER
    http.verify_mode = OpenSSL::SSL::VERIFY_NONE

This is a HTTPS client that uses full verification of the remote host if we have a CA. There’s a small chicken and egg where you have to ask the CA for it’s own certificate where it’s a unverified connection. If this is a problem you need to arrange to put the CA on the machine in a safe manner.

Lets fetch the CA:

def fetch_ca
  return true if has_ca?
  req = Net::HTTP::Get.new("/puppet-ca/v1/certificate/ca", "Content-Type" => "text/plain")
  resp, _ = http.request(req)
  if resp.code == "200"
    File.open(ca_path, "w", Ob0644) {|f| f.write(resp.body)}
    puts("Saved CA certificate to %s" % ca_path)
    abort("Failed to fetch CA from %s: %s: %s" % [@ca, resp.code, resp.message])

At this point we have the CA and saved it, future requests will be verified against this CA. If you put the CA there using some other means this will do nothing.

Now we need to start making our CSR, first we have to make a private key, this is a 4096 bit key saved in pem format:

def write_key
  key = OpenSSL::PKey::RSA.new(4096)
  File.open(key_path, "w", Ob0640) {|f| f.write(key.to_pem)}

And the CSR needs to be made using this key, Puppet CSRs are quite simple with few fields filled in, can’t see why you couldn’t fill in more fields and of course it now supports extensions, I didn’t add any of those here, just a OU:

def write_csr(key)
  csr = OpenSSL::X509::Request.new
  csr.version = 0
  csr.public_key = key.public_key
  csr.subject = OpenSSL::X509::Name.new(
      ["CN", @certname, OpenSSL::ASN1::UTF8STRING],
      ["OU", "my org", OpenSSL::ASN1::UTF8STRING]
  csr.sign(key, OpenSSL::Digest::SHA1.new)
  File.open(csr_path, "w", Ob0644) {|f| f.write(csr.to_pem)}

Let’s combine these to make the key and CSR and send the request to the Puppet CA, this request is verified using the CA:

def request_cert
  req = Net::HTTP::Put.new("/puppet-ca/v1/certificate_request/%s?environment=production" % @certname, "Content-Type" => "text/plain")
  req.body = write_csr(write_key)
  resp, _ = http.request(req)
  if resp.code == "200"
    puts("Requested certificate %s from %s" % [@certname, @ca])
    abort("Failed to request certificate from %s: %s: %s: %s" % [@ca, resp.code, resp.message, resp.body])

You’ll now have to sign the cert on your Puppet CA as normal, or use autosign, nothing new here.

And finally you can attempt to fetch the cert, this method is designed to return false if the cert is not yet ready on the master – ie. not signed yet.

def attempt_fetch_cert
  return true if has_cert?
  req = Net::HTTP::Get.new("/puppet-ca/v1/certificate/%s" % @certname, "Content-Type" => "text/plain")
  resp, _ = http.request(req)
  if resp.code == "200"
    File.open(cert_path, "w", Ob0644) {|f| f.write(resp.body)}
    puts("Saved certificate to %s" % cert_path)

Pulling this all together you have some code to make keys, CSR etc, cache the CA and request a cert is signed, it will then do a wait for cert like Puppet does till things are signed.

def main
  abort("Already have a certificate '%s', cannot continue" % @certname) if has_cert?
  if already_requested?
    puts("Certificate %s has already been requested, attempting to retrieve it" % @certname)
    puts("Requesting certificate for '%s'" % @certname)
  puts("Waiting up to 120 seconds for it to be signed")
  12.times do |time|
    print "Attempting to download certificate %s: %d / 12\r" % [@certname, time]
    break if attempt_fetch_cert
    sleep 10
  abort("Could not fetch the certificate after 120 seconds") unless has_cert?
  puts("Certificate %s has been stored in %s" % [@certname, ssl_dir])

Hiera Node Classifier 0.7


A while ago I released a Puppet 4 Hiera based node classifier to see what is next for hiera_include(). This had the major drawback that you couldn’t set an environment with it like with a real ENC since Puppet just doesn’t have that feature.

I’ve released a update to the classifier that now include a small real ENC that takes care of setting the environment based on certname and then boots up the classifier on the node.


ENCs tend to know only about the certname, you could imagine getting most recent seen facts from PuppetDB etc but I do not really want to assume things about peoples infrastructure. So for now this sticks to supporting classification based on certname only.

It’s really pretty simple, lets assume you are wanting to classify node1.example.net, you just need to have a node1.example.net.yaml (or JSON) file somewhere in a path. Typically this is going to be in a directory environment somewhere but could of course also be a site wide hiera directory.

In it you put:

classifier::environment: development

And this will node will form part of that environment. Past that everything in the previous post just applies so you make rules or assign classes as normal, and while doing so you have full access to node facts.

The classifier now expose some extra information to help you determine if the ENC is in use and based on what file it’s classifying the node:

  • $classifier::enc_used – boolean that indicates if the ENC is in use
  • $classifier::enc_source – path to the data file that set the environment. undef when not found
  • $classifier::enc_environment – the environment the ENC is setting

It supports a default environment which you configure when configuring Puppet to use a ENC as below.

Configuring Puppet

Configuring Puppet is pretty simple for this:

node_terminus = exec
external_nodes = /usr/local/bin/classifier_enc.rb --data-dir /etc/puppetlabs/code/hieradata --node-pattern nodes/%%.yaml

Apart from these you can do –default development to default to that and not production and you can add –debug /tmp/enc.log to get a bunch of debug output.

The data-dir above is for your classic Hiera single data dir setup, but you can also use globs to support environment data like –data-dir /etc/puppetlabs/code/environments/*/hieradata. It will now search the entire glob until it finds a match for the certname.

That’s really all there is to it, it produce a classification like this:

environment: production
    enc_used: true
    enc_source: /etc/puppetlabs/code/hieradata/node.example.yaml
    enc_environment: production


That’s really all there is to it, I think this might hit a high percentage of user cases and bring a key ability to the hiera classifiers. It’s a tad annoying there is no way really to do better granularity than just per node here, I might come up with something else but don’t really want to go too deep down that hole.

In future I’ll look about adding a class to install the classifier into some path and configure Puppet, for now that’s up to the user. It’s shipped in the bin dir of the module.

A Puppet 4 Hiera Based Node Classifier


When I first wrote Hiera I included a simple little hack called hiera_include() that would do a Array lookup and include everything it found. I only included it even because include at the time did not take Array arguments. In time this has become quite widely used and many people do their node classification using just this and the built in hierarchical nature of Hiera.

I’ve always wanted to do better though, like maybe write an actual ENC that uses Hiera data keys on the provided certname? Seemed like the only real win would be to be able to set the node environment from Hiera, I guess this might be valuable enough on it’s own.

Anyway, I think the ENC interface is really pretty bad and should be replaced by something better. So I’ve had the idea of a Hiera based classifier in my mind for years.

Some time ago Ben Ford made a interesting little hack project that used a set of rules to classify nodes and this stuck to my mind as being quite a interesting approach. I guess it’s a bit like the new PE node classifier.

Anyway, so I took this as a starting point and started working on a Hiera based classifier for Puppet 4 – and by that I mean the very very latest Puppet 4, it uses a bunch of the things I blogged about recently and the end result is that the module is almost entirely built using the native Puppet 4 DSL.

Simple list-of-classes based Classification

So first lets take a look at how this replaces/improves on the old hiera_include().

Not really much to be done I am afraid, it’s an array with some entries in it. It now uses the Knockout Prefix features of Puppet Lookup that I blogged about before to allow you to exclude classes from nodes:

So we want to include the sysadmins and sensu classes on all nodes, stick this in your common tier:

# common.yaml
 - sysadmins
 - sensu

Then you have some nodes that need some more classes:

# clients/acme.yaml
 - acme_sysadmins

At this point it’s basically same old same old, but lets see if we had some node that needed Nagios and not Sensu:

# nodes/example.net.yaml
 - --sensu
 - nagios

Here we use the knockout prefix of to remove the sensu class and add the nagios one instead. That’s already a big win from old hiera_include() but to be fair this is just as a result of the new Lookup features.

It really gets interesting later when you throw in some rules.

Rule Based Classification

The classifier is built around a set of Classifications and these are made up of one or many rules per Classification which if they match on a host means a classification applies to the node. And the classifications can include classes and create data.

Here’s a sample rule where I want to do some extra special handling of RedHat like machines. But I want to handle VMs different from Physical machines.

# common.yaml
  RedHat VMs:
    match: all
      - fact: "%{facts.os.family}"
        operator: ==
        value: RedHat
      - fact: "%{facts.is_virtual}"
        operator: ==
        value: "true"
      redhat_vm: true
      - centos::vm
      - fact: "%{facts.os.family}"
        operator: ==
        value: RedHat
      redhat_os: true
      - centos::common

This shows 2 Classifications one called “RedHat VMs” and one just “RedHat”, you can see the VMs one contains 2 rules and it sets match: all so they both have to match.

End result here is that all RedHat machines get centos::common and RedHat VMs also get centos::vm. Additionally 2 pieces of data will be created, a bit redundant in this example but you get the idea.

Using the Classifier

So using the classifier in the basic sense is just like hiera_include():

node default {
  include classifier

This will process all the rules and include the resulting classes. It will also expose a bunch of information via this class, the most interesting is $classifier::data which is a Hash of all the data that the rules emit. But you can also access the the included classes via $classifier::classes and even the whole post processed classification structure in $classifier::classification. Some others are mentioned in the README.

You can do very impressive Hiera based overrides, here’s an example of adjusting a rule for a particular node:

# clients/acme.yaml
  RedHat VMs:
      - some::other
      extra_data: true

This has the result that for this particular client additional data will be produced and additional classes will be included – but only on their RedHat VMs. You can even use the knockout feature here to really adjust the data and classes.

The classes get included automatically for you and if you set classifier::debug you’ll get a bunch of insight into how classification happens.

Hiera Inception

So at this point things are pretty neat, but I wanted to both see how the new Data Provider API look and also see if I can expose my classifier back to Hiera.

Imagine I am making all these classifications but with what I shown above it’s quite limited because it’s just creating data for the $classifier::data hash. What you really want is to create Hiera data and be able to influence Automatic Parameter Lookup.

So a rule like:

# clients/acme.yaml
      centos::common::selinux: permissive

Here I am taking the earlier RedHat rule and setting centos::common::selinux: permissive, now you want this to be Data that will be used by the Automatic Parameter Lookup system to set the selinux parameter of the centos::common class.

You can configure your Environment with this hiera.yaml

# environments/production/hiera.yaml
version: 4
datadir: "hieradata"
  - name: "%{trusted.certname}"
    backend: "yaml"
  - name: "classification data"
    backend: "classifier"
  # ... and the rest

Here I allow node specific YAML files to override the classifier and then have a new Data Provider called classifier that expose the classification back to Hiera. Doing it this way is super important, the priority the classifier have on a site is not a single one size fits all choice, doing it this way means the site admins can decide where in their life classification site so it best fits their workflows.

So this is where the inception reference comes in, you extract data from Hiera, process it using the Puppet DSL and expose it back to Hiera. At first thought this is a bit insane but it works and it’s really nice. Basically this lets you completely redesign hiera from something that is Hierarchical in nature and turn it into a rule based system – or a hybrid.

And you can even test it from the CLI:

% puppet lookup --compile --explain centos::common::selinux
Merge strategy first
  Data Binding "hiera"
    No such key: "centos::common::selinux"
  Data Provider "Hiera Data Provider, version 4"
    ConfigurationPath "environments/production/hiera.yaml"
    Merge strategy first
      Data Provider "%{trusted.certname}"
        Path "environments/production/hieradata/dev2.devco.net.yaml"
          Original path: "%{trusted.certname}"
          No such key: "centos::common::selinux"
      Data Provider "classification data"
        Found key: "centos::common::selinux" value: "permissive"
      Merged result: "permissive"
  Merged result: "permissive"

I hope to expose here which rule provided this data like the other lookup explanations do.

Clearly this feature is a bit crazy, so consider this a exploration of what’s possible rather than a strong endorsement of this kind of thing πŸ™‚


Implementing this has been pretty interesting, I got to use a lot of the new Puppet 4 features. Like I mentioned all the data processing, iteration and deriving of classes and data is done using the native Puppet DSL, take a look at the functions directory for example.

It also makes use of the new Type system and Type Aliases all over the place to create a strong schema for the incoming data that gets validated at all levels of the process. See the types directory.

The new Modules in Data is used to set lookup strategies so that there are no manual calling of lookup(), see the module data.

Writing a Data Provider ie. a Hiera Backend for the new lookup system is pretty nice, I think the APIs around there is still maturing so definitely bleeding edge stuff. You can see the bindings and data provider in the lib directory.

As such this module only really has a hope of working on Puppet 4.4.0 at least, and I expect to use new features as they come along.


There’s a bunch more going on, check the module README. It’s been quite interesting to be able to really completely rethink how Hiera data is created and what a modern take on classification can achieve.

With this approach if you’re really not too keen on the hierarchy you can totally just use this as a rules based Hiera instead, that’s pretty interesting! I wonder what other strategies for creating data could be prototyped like this?

I realise this is very similar to the PE node classifier but with some additional benefits in being exposed to Hiera via the Data Provider, being something you can commit to git and being adjustable and overridable using the new Hiera features I think it will appeal to a different kind of user. But yeah, it’s quite similar. Credit to Ben Ford for his original Ruby based implementation of this idea which I took and iterated on. Regardless the ‘like a iTunes smart list’ node classifier isn’t exactly a new idea and have been discussed for literally years πŸ™‚

You can get the module on the forge as ripienaar/classifier and I’d greatly welcome feedback and ideas.

Puppet 4 Type Aliases


Back when I first took a look at Puppet 4 features I explored the new Data Types and said:

Additionally I cannot see myself using a Struct like above in the argument list – to which Henrik says they are looking to add a typedef thing to the language so you can give complex Struc’s a more convenient name and use that. This will help that a lot.

And since Puppet 4.4.0 this has now become a reality. So a quick post to look at that.

The Problem

I’ve been writing a Hiera based node classifier both to scratch and itch and to have something fairly complex to explore the new features in Puppet 4.

The classifier takes a set of classification rules and produce classifications – classes to include and parameters – from there. Here’s a sample classification:

  RedHat VMs:
    match: all
      - fact: "%{facts.os.family}"
        operator: ==
        value: RedHat
      - fact: "%{facts.is_virtual}"
        operator: ==
        value: "true"
      redhat_vm: true
      centos::vm::someprop: someval
      - centos::vm

This is a classification rule that has 2 rules to match against machines running RedHat like operating systems and that are virtual. In that case if both these are true it will:

  • Include the class centos::vm
  • Create some data redhat_vm => true and centos::vm::someprop => someval

You can have an arbitrary amount of classifications made up of a arbitrary amount of rules. This data lives in hiera so you can have all sorts of merging, overriding and knock out fun with it.

The amazing thing is since Puppet 4.4.0 there is now no Ruby code involved in doing what I said above, all the parsing, looping, evaluating or rules and building of data structures are all done using functions written in the pure Puppet DSL.

There’s some Ruby there in the form of a custom backend for the new lookup based hiera system – but this is experimental, optional and a bit crazy.

Anyway, so here’s the problem, before Puppet 4.4.0 my main class had this in:

class classifier (
      match    => Enum["all", "any"],
      rules    => Array[
          fact     => String,
          operator => Enum["==", "=~", ">", " =>", "<", "<="],
          value    => Data,
          invert   => Optional[Boolean]
      data     => Optional[Hash[Pattern[/\A[a-z0-9_][a-zA-Z0-9_]*\Z/], Data]],
      classes  => Array[Pattern[/\A([a-z][a-z0-9_]*)?(::[a-z][a-z0-9_]*)*\Z/]]
  ] $rules = {}
) {

This describes the full valid rule as a Puppet Type. It’s pretty horrible. Worse I have a number of functions and classes all that receives the full classification or parts of it and I’d have to duplicate all this all over.

The Solution

So as of yesterday I can now make this a lot better:

class classifier (
  Classifier::Classifications  $rules = {},
) {

to do this I made a few files in the module:

# classifier/types/matches.pp
type Classifier::Matches = Enum["all", "any"]
# classifier/types/classname.pp
type Classifier::Classname = Pattern[/\A([a-z][a-z0-9_]*)?(::[a-z][a-z0-9_]*)*\Z/]

and a few more, eventually ending up in:

# classifier/types/classification.pp
type Classifier::Classification = Struct[{
  match    => Classifier::Matches,
  rules    => Array[Classifier::Rule],
  data     => Classifier::Data,
  classes  => Array[Classifier::Classname]

Which you can see solves the problem quite nicely. Now in classes and functions where I need lets say just a Rule all I do is use Classifier::Rule instead of all the crazy.

This makes the native Puppet Data Types perfectly usable for me, well worth adopting these.

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