Clarify the Glance/metadefs relationship
I've answered a few questions recently for people who assumed that since the metadefs service lives on the Glance endpoint, metadefs have some kind of special relationship to images. I think the metadefs section of the api-ref makes it clear that this is not the case (though it's not mentioned at all on the Images part of the api-ref). So here's an attempt to clarify issue (without being too intrusive) right at the top of the Glance docs landing page. Change-Id: I3dfbb09862acedb265a5a4557749bf52f6add5f4
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@ -23,7 +23,10 @@ About Glance
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The Image service (glance) project provides a service where users can upload
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The Image service (glance) project provides a service where users can upload
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and discover data assets that are meant to be used with other services.
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and discover data assets that are meant to be used with other services.
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This currently includes images and metadata definitions.
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This currently includes *images* and *metadata definitions*.
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Images
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------
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Glance image services include discovering, registering, and
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Glance image services include discovering, registering, and
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retrieving virtual machine (VM) images. Glance has a RESTful API that allows
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retrieving virtual machine (VM) images. Glance has a RESTful API that allows
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@ -35,6 +38,27 @@ VM images made available through Glance can be stored in a variety of
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locations from simple filesystems to object-storage systems like the
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locations from simple filesystems to object-storage systems like the
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OpenStack Swift project.
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OpenStack Swift project.
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Metadata Definitions
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--------------------
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Glance hosts a *metadefs* catalog. This provides the OpenStack community
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with a way to programmatically determine various metadata key names and
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valid values that can be applied to OpenStack resources.
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Note that what we're talking about here is simply a *catalog*; the keys and
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values don't actually do anything unless they are applied to individual
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OpenStack resources using the APIs or client tools provided by the services
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responsible for those resources.
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It's also worth noting that there is no special relationship between the
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Image Service and the Metadefs Service. If you want to apply the keys and
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values defined in the Metadefs Service to images, you must use the Image
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Service API or client tools just as you would for any other OpenStack
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service.
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Design Principles
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-----------------
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Glance, as with all OpenStack projects, is written with the following design
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Glance, as with all OpenStack projects, is written with the following design
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guidelines in mind:
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guidelines in mind:
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