[Openstack-operators] Nodes and configurations management in Puppet

Michael Chapman woppin at gmail.com
Sat Sep 27 10:58:10 UTC 2014

On Sat, Sep 27, 2014 at 4:03 AM, 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/
> --
> Mathieu
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> OpenStack-operators at lists.openstack.org
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I am working towards a client side ENC that queries a Consul [1] k/v store,
and building similar scripting to what I built for puppet_openstack_builder
so that I can import hiera -> consul and set ACLs + node classifications.
An ENC would also avoid the 'everything must be a string' issues in hiera,
although maybe bodepd will finally solve that with this [2]. Consul already
has a decent dashboard (though not as nice as the puppet enterprise one) so
I should be able to leverage that.

Consul might similarly provide part of a suitable mechanism for discovery,
although the nature of Puppet and its expectation that data is available at
catalog compile time is a significant barrier to implementing this sanely,
since functions and facts are evaluated before resources, and resources
don't have a way to feed data back. My thoughts to mitigate this were to
split into smaller profiles and allow nodes to signal each other indicating
that a specific profile should be state-checked via running puppet, so that
I could watch consul and listen for messages and apply new data quickly,
but splitting catalogs sensibly is quite difficult.

I have a talk scheduled for the Paris summit on how I'm doing that using
Serf for the message bit, but I'm still not completely convinced it's
actually the best way to go about things, and I have a long way to go still
on implementation. Serf/Consul are also very new pieces of software so I'm
sure I'll hit more issues as I go.

I have heard there are others attempting similar things with etcd.

[1] http://www.consul.io/
[2] https://github.com/puppetlabs/hiera/pull/213
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