[Openstack] Allowing clients to pass capability requests through tags?

Justin Santa Barbara justin at fathomdb.com
Thu Feb 10 21:37:18 UTC 2011

Does anyone have any thoughts/objections on the blueprint I posted for
allowing clients to pass capability-requests through tags?  I'm planning on
starting implementation soon, so if people think this is a bad idea I'd
rather know before I start coding!


a quick TLDR:
API clients need a way to request e.g. placement of machines near each other
/ near volumes, or that a volume be created with a particular RAID level, or
that a machine be created in a HIPAA compliant environment.  (This is
complementary to the work on hierarchical zones & URL naming, I believe)

I propose using the instance tags for this, e.g. specifying
openstack:near=vol-000001 when creating an instance to request locating the
instance 'close to' that volume.

By default these requests would be best-effort and ignored-if-unknown; if
the client wants to specify that something is required and should fail if
not understood or not satisfiable, they could use a "+" e.g.

Controversially (?), this would not be supported for clients using the AWS
API, because tags can only be specified once the instance has already been

Feedback appreciated!

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