[Openstack-operators] Nodes and configurations management in Puppet

Mathieu Gagné mgagne at iweb.com
Fri Sep 26 18:03:50 UTC 2014

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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