On 26/11/13 03:26, Keith Bray wrote:
On 11/25/13 5:46 PM, "Clint Byrum" <cl...@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?
The part where it's used for something. What I'm hearing in this thread
is "We need this for a template catalog, but we're not going to talk
about that until later. Trust us, though, we really need it."
That's a problem, because none of this stuff makes sense except in the
context of the template catalog. What does the template catalog do? Who
writes the templates in the catalog? Why is the template catalog not
backed by git? Who can say which parts of the solution belong in the
template catalog and which in Heat when we don't even know what it's a
solution to?
What I am seeing is that the use case of meta data is not what is being
I'm contesting it:
https://review.openstack.org/#/c/56703/7/doc/source/template_guide/hot_spec.rst
The problem here isn't that the process wasn't followed, it's that all
of these things - one-shot outputs, operator-specific structured
metadata sections in templates, APIs to report versions of randomly
selected daemons - are fundamentally bad ideas. And they're all bad in
exactly the same way: they demand that Heat implement something that it
can only do in a half-baked manner, because it's slightly easier (or
seems slightly easier) than implementing something in some external tool
that can work.
It's difficult to escape the conclusion that these features have been
decided upon behind closed doors with the community excluded, by people
who are not especially familiar with Heat, with a view to minimising the
effort required to implement some other (proprietary?) thing and not
necessarily to coming up with the best implementation. If this is your
development process then you are Doing Open Source Wrong. At a very
minimum you need to work about 10x harder to explain all of these design
decisions - in particular the reasons why the obvious alternatives that
don't appear to have been considered are insufficient - to the
community. It's much, much easier, though, to just do your design in the
open with community involvement.
Take this metadata section idea. (Please!) Let's step back and examine
the very last decision in the chain - assume for a moment that we accept
that this metadata needs to be included in the template. There are three
obvious ways to do that:
1) Include them as YAML comments
2) Include them in the body of the template
3) Include them as a separate YAML document in the same file
How many of those were actually considered? My bet is only #2. It
doesn't really matter though, because there is not one word of design
documentation that would help me understand the reasons for rejecting #1
& #3 (neither of which require any changes to Heat or the template
format). How can I have confidence that #2 is the correct solution to
the problem? Especially if I don't agree (I don't)?
The number of options not considered grows (and my confidence in the
solution shrinks) exponentially as you step all the way back through the
chain of undocumented decisions to the actual thing that drove this idea.
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
I contested that first because without knowing what the feature is even
for, there's nothing else to contest.
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
It seems clear that we have to communicate better to new contributors
what the expectations are around getting features in. But I would be
really sad if we have to jump straight in to the sort of legalistic
processes that some of the larger OpenStack programs follow. This is
still a relatively small project; we should be able to handle these
questions by talking to each other.
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).
-1
There is precedence for an optional metadata section that can contain
any
As Clint said, you're comparing APIs to templates. Those are very different.
end-user data in other Openstack projects and it is necessary in order
to
iterate quickly and provide value to Heat.
Non sequitur.
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
First of all, "short_description" is a dreadful name for something that
is basically tags.
Secondly, these are tags in the template catalog. So why are they
incorporated in the template, and not stored in the template catalog?
Finally, if you really want this it can be trivially implemented using
comments.
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
What's most useful in portability is placing the minimum requirements
(especially undocumented and/or non-standard requirements) on the
template author, since you can't control the template author.
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
I view it as an open invitation to fragment the template format and the
ecosystem.
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.
I don't understand all this stuff about 'portability'. From your
previous descriptions of the template catalog, it sounded like it's for
templates hand-picked by the operator. Why would one operator want to
import the tags defined by another operator anyway? And Why wouldn't
that just be a git clone of the backing repository? And how does any of
this make the template more "portable"???
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
Put it in a comment.
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
If it needs to be available for a deployed stack (you haven't made an
argument for this yet) then add it into the template-proper. If Heat
needs to read it then some sort of wild-west schemaless metadata area is
definitely not the place to put it.
Alternately, maybe we need to look at storing templates in such a way
that the comments are preserved. I would definitely look favourably on a
blueprint to that effect.
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
Please don't raise a blueprint for every patch. e.g. a feature and its
documentation
(https://blueprints.launchpad.net/heat/+spec/update-stack-metadata-spec)
are not two blueprints.
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)
If it didn't come from the catalog provided by the operator, what are
the chances that it contains this information anyway? How is the average
template author going to know about the schema for the metadata read by
your proprietary tool?
(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.
This sounds like a good argument for Heat preserving comments.
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.
What's really going to limit portability is having multiple overlapping
undocumented proprietary schemas for parts of the template. I actually
think this has the potential to damage the Heat ecosystem, and that's
one of the reasons I'm pushing back on it.
regards,
Zane.
_______________________________________________
OpenStack-dev mailing list
OpenStack-dev@lists.openstack.org
http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
