[Openstack-operators] Nodes and configurations management in Puppet

Michael Dorman mdorman at godaddy.com
Fri Oct 3 03:50:05 UTC 2014

We maintain a fairly flat hiera structure, which largely is due to our OS
infrastructure still being pretty simple.

Like Clayton & Matt, we use a ³world² attribute to indicate dev/test/prod.
 (Although in hindsight, I like the Œechelon¹ term a lot better.  We did
the same exercise of thinking of synonyms for Œenvironment.¹)  So the
structure looks like:

- %{::world}/%{::clientcert}
  - %{::world}
  - global

The global file is empty, and almost all of the config is stored in the
world file.  Over time, this has led to hiera sprawl so the world files
have gotten quite messy.  And there is a lot of items that aren¹t unique
across worlds, so should really be in a global file.  But, at the same
time, this gives us a [mostly] single source of truth and avoids the ³grep
-R² issue Joe described.

ENC at this point is done by specifying a Œrole¹ parameter in the
individual clientcert file for each node.  This is a major downside, and
doesn¹t scale, so we need to figure out something better.  Maybe we can
come up with a hostname scheme to encode the info there, like others have

We run all masterless, for a variety of reasons (which limits ENC options,
too.)  Ansible is used to kick off runs across the environment.  r10k
deploys the Puppet environments (Œmaster¹ and Œprod¹ which correspond to
git branches), heira data, and all the modules.  Hiera data is in a
separate (private) git repo, but there¹s only a master branch there.

I¹ve been a big fan of the role/profile model, too, and it¹s worked well
for us.  One thing I¹ve thought about is specifying a list of profile
classes for each node or node type in hiera, rather than maintaining a
mostly static role module.  Then we can just hiera_include(), which is the
method we use in site.pp to include the role class now.  I¹d be interested
in others thoughts on this idea.  I can¹t really think of a compelling
reason to switch, other than it¹s kind of clever.


On 9/26/14, 12:03 PM, "Mathieu Gagné" <mgagne at iweb.com> wrote:

>Hi Joe,
>Your experience and story about Puppet and OpenStack makes me feel like
>you are a long lost co-worker. :)
>On 2014-09-25 10:30 PM, Joe Topjian wrote:
>> Hiera takes the cake for my love/hate of Puppet. I try really hard to
>> keep the number of hierarchies small and even then I find it awkward
>> sometimes. I love the concept of Hiera, but I find it can be
>> unintuitive.
>Same here. The aspect I hate about Hiera is that files become very big
>and unorganized very fast due to the quantity of configs. So you try to
>split them in multiples files instead and then you have the problem you
>describe below...
> > Similar to the other replies, I have a "common" hierarchy
>> where 90% of the data is stored. The other hierarchies either override
>> "common" or append to it. When I need to know where a parameter is
>> ultimately configured, I find myself thinking "is that parameter common
>> across everything or specific to a certain location or node, and if so,
>> why did I make it specific?", then doing a "grep -R" to find where it's
>> located, and finally thinking "oh right - that's why it's there".
>Yep. That's the feeling I was referring to when I said "heart attack".
>And now, try to form a new co-worker and explain him how it's organized:
>"Oh, I felt the file was too big so I split it in a hope to restore
>sanity which it did with limited success."
>The other difficulty is the management of "common" configs like keystone
>auth URL. Multiple services need this value, yet their might be split in
>multiple files and the YAML anchor hack [1] I used so far does not work
>across YAML files. Same for database configs which are needed by the
>database server (to provision the user) and services (for the database
>connection string).
>> Another area of Puppet that I'm finding difficult to work with is
>> configuring HA environments. There are two main pain points here and
>> they're pretty applicable to using Puppet with OpenStack:
> >
>> The other HA pain point is creating many-to-one configurations [...]
>> I think a cleaner way of doing this is to introduce service discovery
>> into my environment, but I haven't had time to look into this in more
>> detail.
>I wholly agree with you and that's a concept I'm interested to explore.
>Come to think of it, it strangely looks like the "dependency inversion
>principle" in software development.
>I however feel that an external ENC becomes inevitable to achieve this
>ease of use. Unfortunately, each time I looked into it, I rapidly get
>lost in my dream of a simple dashboard to manage everything. I feel I
>rapidly come to the limits of what exported resources, Hiera and
>puppetdb can do.
>One idea would be to export an haproxy::listen resource from one of the
>controller (which now becomes a pet as you said) and realize it on the
>HAProxy nodes with its associated haproxy::member resources.
>> I should mention that some of these HA pains can be resolved by just
>> moving all of the data to the HAProxy nodes themselves. So when I want
>> to add a new service, such as RabbitMQ, to HAProxy, I add the RabbitMQ
>> settings to the HAProxy role/profiles. But I want HAProxy to be "dumb"
>> about what it's hosting. I want to be able to use it in a Juju-like
>> fashion where I can introduce any arbitrary service and HAProxy
>> configures itself without prior knowledge of the new service.
>Yes! How do you guys think we can implement such discovery?
>With Nova cells, this problem became much more apparent due to
>inter-relations between the API cell and compute cells. The API cell has
>to know about the compute cells and vice versa.
>> In general, though, I really enjoy working with Puppet. Our current
>> Puppet configurations allow us to stand up test OpenStack environments
>> with little manual input as well as upgrade to newer releases of
>> OpenStack with very little effort.
>Yes, I really enjoy Puppet too. After all hardware/infrastructure
>aspects are figured out, we are able to bootstrap a new OpenStack region
>in less than an hour.
>To summarize my current pain points:
>- Out of control Hiera configuration files
>- Lack of service auto-discovery
>[1] https://dmsimard.com/2014/02/15/quick-hiera-tips/
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