On Mon, Oct 04, 2010 at 02:52:34PM +0100, Michael Gundlach wrote: > Hi Ewan, > On Sat, Oct 2, 2010 at 10:46 AM, Ewan Mellor <[email protected]> > wrote: > > On Sat, Oct 02, 2010 at 03:29:57PM +0100, Ewan Mellor wrote: > > > In the documentation for the nova.virt layer (in nova.virt.fake) I > wrote: > > > > * * An instance has an ID, which is the identifier chosen by Nova to > represent > > * * the instance further up the stack. *This is unfortunately also > called a > > * * 'name' elsewhere. *As far as this layer is concerned, 'instance > ID' and > > * * 'instance name' are synonyms. > > > > * * Note that the instance ID or name is not human-readable or > > * * customer-controlled -- it's an internal ID chosen by Nova. *At the > > * * nova.virt layer, instances do not have human-readable names at all > -- such > > * * things are only known higher up the stack. > > > > Is this true any longer? *Looking at nova.db.sqlalchemy.Instance I see > > fields named id, ec2_id, display_name, and display_description. *What > are > > the semantics of these fields? *How far are these concepts supposed to > > propagate down the stack? > > id is the primary key in sqlalchemy -- not stable if we move b/w databases > or shard, so not a candidate for uniquely identifying the instance for all > time. > ec2_id USED TO be the string that the EC2 API used to identify the > instance to the user. > ec2_id is being renamed (in a branch that hasn't hit trunk yet) to > 'internal_id' and becoming a long int. *That is the canonical identifier > for an instance, unique for all time and unchanging throughout the life of > the instance. > The EC2 and Rackspace API modules convert 'internal_id' to and from an > API-specific form suitable for showing to users -- in the EC2 case, it's > converted to* > **"i-%s" % base_36_representation_of(internal_id) > I've seen some code referring to 'ec2_id' as 'instance_id' (in method > params and such), which is just confusing; I'll be renaming those to > internal_id for consistency before Austin. > I don't know what display_name and display_description are about.
Thanks Michael. It would be great to see this in some doccomments in the code somewhere. I agree with Jay's comments elsewhere in this thread -- it seems a better idea to use a UUID for your internal_id, rather than a long int. That way, the ID is an extra 64 bits longer, so you can generate them randomly on independent nodes without worrying about collisions. Cheers, Ewan. _______________________________________________ Mailing list: https://launchpad.net/~nova Post to : [email protected] Unsubscribe : https://launchpad.net/~nova More help : https://help.launchpad.net/ListHelp
