Open Stack

Denis,

The scope of the metadata api goes beyond just using the glance metadata.
The metadata can be used for instances and and other objects to add extra
data like tags or something else that maybe a UI might want to use. We need
this feature either way.

-Craig


On Thu, Jul 24, 2014 at 12:17 PM, Amrith Kumar <amrith at tesora.com> wrote:

> Speaking as a ‘database guy’ and a ‘Trove guy’, I’ll say this; “Metadata”
> is a very generic term and the meaning of “metadata” in a database context
> is very different from the meaning of “metadata” in the context that Glance
> is providing.
>
>
>
> Furthermore the usage and access pattern for this metadata, the frequency
> of change, and above all the frequency of access are fundamentally
> different between Trove and what Glance appears to be offering, and we
> should probably not get too caught up in the project “title”.
>
>
>
> We would not be “reinventing the wheel” if we implemented an independent
> metadata scheme for Trove; we would be implementing the right kind of when
> for the vehicle that we are operating. Therefore I do not agree with your
> characterization that concludes that:
>
>
>
> >> given goals at [1] are out of scope of Database program, etc
>
>
>
> Just to be clear, when you write:
>
>
>
> >> Unfortunately, we’re(Trove devs) are on half way to metadata …
>
>
>
> it is vital to understand that our view of “metadata” is very different
> from (for example, a file system’s view of metadata, or potentially
> Glance’s view of metadata). For that reason, I believe that your comments
> on https://review.openstack.org/#/c/82123/16 are also somewhat extreme.
>
>
>
> Before postulating a solution (or “delegating development to Glance
> devs”), it would be more useful to fully describe the problem being solved
> by Glance and the problem(s) we are looking to solve in Trove, and then we
> could have a meaningful discussion about the right solution.
>
>
>
> I submit to you that we will come away concluding that there is a round
> peg, and a square hole. Yes, one will fit in the other but the final
> product will leave neither party particularly happy with the end result.
>
>
>
> -amrith
>
>
>
> *From:* Denis Makogon [mailto:dmakogon at mirantis.com]
> *Sent:* Thursday, July 24, 2014 9:33 AM
> *To:* OpenStack Development Mailing List
> *Subject:* [openstack-dev] [Glance][Trove] Metadata Catalog
>
>
>
> Hello, Stackers.
>
>
>      I’d like to discuss the future of Trove metadata API. But first small
> history info (mostly taken for Trove medata spec, see [1]):
>
> *Instance metadata is a feature that has been requested frequently by our
> users. They need a way to store critical information for their instances
> and have that be associated with the instance so that it is displayed
> whenever that instance is listed via the API. This also becomes very usable
> from a testing perspective when doing integration/ci. We can utilize the
> metadata to store things like what process created the instance, what the
> instance is being used for, etc... The design for this feature is modeled
> heavily on the Nova metadata API with a few tweaks in how it works
> internally.*
>
>     And here comes conflict. Glance devs are working on “Glance Metadata
> Catalog” feature (see [2]). And as for me, we don’t have to* “reinvent
> the wheel” for Trove. *It seems that we would be able
>
> to use Glance API to interact with   Metadata Catalog. And it seems to be
> redundant to write our own API for metadata CRUD operations.
>
>
>
>     From Trove perspective, we need to define a list concrete use cases
> for metadata usage (eg given goals at [1] are out of scope of Database
> program, etc.).
>
> From development and cross-project integration perspective, we need to
> delegate all development to Glance devs. But we still able to help Glance
> devs with this feature by taking active part in polishing proposed spec
> (see [2]).
>
>
>
>     Unfortunately, we’re(Trove devs) are on half way to metadata - patch
> for python-troveclient already merged. So, we need to consider
> deprecation/reverting of merged and block
>
> merging of proposed ( see [3]) patchsets in favor of Glance Metadata
> Catalog.
>
>
>
>     Thoughts?
>
> [1] https://wiki.openstack.org/wiki/Trove-Instance-Metadata
>
> [2] https://review.openstack.org/#/c/98554/11
>
> [3] https://review.openstack.org/#/c/82123/
>
>
>
> Best regards,
>
> Denis Makogon
>
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>
>
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