Open Stack

On 11/25/13 5:46 PM, "Clint Byrum" <clint at fewbar.com> wrote:

>Excerpts from Tim Schnell's message of 2013-11-25 14:51:39 -0800:
>> Hi Steve,
>> 
>> As one of the UI developers driving the requirements behind these new
>> blueprints I wanted to take a moment to assure you and the rest of the
>> Openstack community that the primary purpose of pushing these
>>requirements
>> out to the community is to help improve the User Experience for Heat for
>> everyone. Every major UI feature that I have implemented for Heat has
>>been
>> included in Horizon, see the Heat Topology, and these requirements
>>should
>> improve the value of Heat, regardless of the UI.
>> 
>> 
>> Stack/template metadata
>> We have a fundamental need to have the ability to reference some
>> additional metadata about a template that Heat does not care about.
>>There
>> are many possible use cases for this need but the primary point is that
>>we
>> need a place in the template where we can iterate on the schema of the
>> metadata without going through a lengthy design review. As far as I
>>know,
>> we are the only team attempting to actually productize Heat at the
>>moment
>> and this means that we are encountering requirements and requests that
>>do
>> not affect Heat directly but simply require Heat to allow a little
>>wiggle
>> room to flesh out a great user experience.
>> 
>
>Wiggle room is indeed provided. But reviewers need to understand your
>motivations, which is usually what blueprints are used for. If you're
>getting push back, it is likely because your blueprints to not make the
>use cases and long term vision obvious.

Clint, can you be more specific on what is not clear about the use case?
What I am seeing is that the use case of meta data is not what is being
contested, but that the Blueprint of where meta data should go is being
contested by only a few (but not all) of the core devs.  The Blueprint for
in-template metadata was already approved for Icehouse, but now that work
has been delivered on the implementation of that blueprint, the blueprint
itself is being contested:
   https://blueprints.launchpad.net/heat/+spec/namespace-stack-metadata
I'd like to propose that the blueprint that has been accepted go forth
with the code that exactly implements it, and if there are alternative
proposals and appropriate reasons for the community to come to consensus
on a different approach, that we then iterate and move the data (deprecate
the older feature if necessary, e.g. If that decision comes after
Icehouse, else of a different/better implementation comes before Icehouse,
then no harm done).


>
>> There is precedence for an optional metadata section that can contain
>>any
>> end-user data in other Openstack projects and it is necessary in order
>>to
>> iterate quickly and provide value to Heat.
>> 
>
>Nobody has said you can't have meta-data on stacks, which is what other
>projects use.
>
>> There are many use cases that can be discussed here, but I wanted to
>> reiterate an initial discussion point that, by definition,
>> "stack/template_metadata" does not have any hard requirements in terms
>>of
>> schema or what does or does not belong in it.
>> 
>> One of the initial use cases is to allow template authors to categorize
>> the template as a specific "type".
>> 
>>     template_metadata:
>>         short_description: Wordpress
>> 
>>     
>
>Interesting. Would you support adding a "category" keyword to python so
>we don't have to put it in setup.cfg and so that the egg format doesn't
>need that section? Pypi can just parse the python to categorize the apps
>when they're uploaded. We could also have a file on disk for qcow2 images
>that we upload to glance that will define the meta-data.
>
>To be more direct, I don't think the templates themselves are where this
>meta-data belongs. A template is self-aware by definition, it doesn't
>need the global metadata section to tell it that it is WordPress. For
>anything else that needs to be globally referenced there are parameters.
>Having less defined inside the template means that you get _more_ wiggle
>room for your template repository.

Clint, you are correct that the Template does not need to know what it is.
 It's every other service (and users of those services) that a Template
passes through or to that would care to know what it is. We are suggesting
we put that meta data in the template file and expressly ignore it for
purposes of parsing the template language in the Heat engine, so we agree
it not a necessary part of the template.  Sure, we could encode the
metadata info in a separate catalog...  but, take the template out of the
catalog and now all that useful associated data is lost or would need to
be recreated by someone or some service.  That does not make the template
portable, and that is a key aspect of what we are trying to achieve (all
user-facing clients, like Horizon, or humans reading the file, can take
advantage). We don't entirely know yet what is most useful in portability
and what isn't, so meta data in-template provides the "wiggle room"
innovation space to suss that out.  We already know of some specific use
cases of data that we feel are important, which Tim identified one
specific example.. As specific metadata items become popular or prove to
be useful to rely on by the larger community or service operators (public
and private) of Heat, we as a community can drive that information back
into the schema for the template or some portable format mechanism.

>
>I 100% support having a template catalog. IMO it should be glance,
>which is our catalog service in OpenStack. Who cares if nova or heat are
>consuming images or templates. It is just sharable blobs of data and
>meta-data in a highly scalable service. It already has the concept of
>global and tenant-scope. It just needs an image type of 'hot' and then
>heat can start consuming templates from glance. And the template authors
>should maintain some packaging meta-data in glance to communicate to
>users that this is "Wordpress" and "Single-Node". If Glance's meta-data
>is too limiting, expand it! I'm sure image authors and consumers would
>appreciate that.

This is definitely interesting... And takes the long view IMO.  Let me
explain:  I don't anticipate Heat catalog'ing in Glance is something that
has a high chance of getting implemented in the Icehouse timeframe (at
least, not more so than in-template metadata), do you?  From a SOA service
deployer perspective, I'm sure you can appreciate that rolling out new
functionality in Glance to support an Orchestration project use case is
not simple, and requires strong business justification and coordination as
an operator of a cloud.. One worth exploring for sure, but not the go-to
default strategy. I view the metadata change as very minor with little to
no disruption to any service, including Heat (Heat just ignores the
metadata, completely).. This fits very well in an iterative development
model.  New blueprints could be raised, as you suggested, to move metadata
and catalog features into Glance.  My concern is that if we go the Glance
route now, we are encouraging a precedent that we aren't iterative (due to
abandoning an already accepted blueprint in favor of a more complex and
time intensive solution) and that we won't get this implemented within the
current release cycle.

>
>> This would let the client of the Heat API group the templates by type
>> which would create a better user experience when selecting or managing
>> templates. The the end-user could select "Wordpress" and drill down
>> further to select templates with different options, "single node", "2
>>web
>> nodes", etc...
>> 
>
>That is all api stuff, not language stuff.

If this were done solely at the API, it would have to be maintained 1-to-1
with a template (in which case there is an implicit and explicit
association), and exported with the template in order to port the
template. 

>
>> Once a feature has consistently proven that it adds value to Heat or
>> Horizon, then I would suggest that we can discuss the schema for that
>> feature and codify it then.
>> 
>> In order to keep the discussion simple, I am only responding to the need
>> for stack/template metadata at the moment but I'm sure discussions on
>>the
>> management api and template catalog will follow.
>> 
>
>Your example puts the template catalog in front of this feature, and I
>think that exposes this feature as misguided.

I'd like template author and creation date portable so that it goes
wherever the template goes in a portable format that consumers (any
client) of the Heat service can understand.  I'd also like this
information to be available for a deployed stack in Heat, so it is need
not be catalog specific.  If author/creation-date information were only
available in the catalog, then we would have to entirely wrap the Heat API
in another service or risk drift in the data between Heat and the separate
non-wrapping catalog service. Instead of raising a blueprint for every
piece of data that may be useful to deploying this service (some of which
certain folks may not care about [e.g. Many of the folks arguing against
metadata all together], the in-template metadata is, IMO, a suitable
approach to experiment and then we can drive back experiential use-cases
into future improvements (e.g. in-language schema changes or catalog
changes).  At Rackspace we have experience running a nearly identical
service, so we know this data, in this particular place, is a valid use
case for consumers of an Orchestration service.
Example: 
(1) Cloud customer of service operator deploys a template (may or may not
have come from the catalog)
(2) Customer encounters problem with the stack and calls support
(3) Support specialist [not the service operator/developer] is trying to
figure out who to contact for additional help given failures seen with the
stack. The dev team of the service is not the expert in application foo
and did not develop the template. It's not a Heat issue, it's a
template/application foo issue.

Having this detail come from Glance, as you pointed out, would be great.
But, my hope is that many folks will develop and share templates, and the
folks developing templates won't necessarily be running glance or have
access to upload their own images into glance (that is a service operator
choice).  If we force this basic info to glance, we are limiting our
portability (and therefore adoption story) of Heat.

-Keith