I'm working on a patch to at least make the glance UUID -> S3 image ID not totally depend on an on-demand insertion order as it does now.
Agreed, collisions are inevitable given the relative domain and range sizes (122 unique bit UUID versus 32-bit hex string) - in testing, the first colliding UUID tends to occur after ~75k-80k images IDs have been generated. So at least it would be useful for smaller deployments to have a semi-predictable ID mapping (modulo collisions). For larger deployments, the mapping data to be replicated could be much reduced by limiting it to the colliding IDs. Cheers, Eoghan > Alternatively, we could just consider the ec2 mapping layer to be > global data that must be replicated somehow across the system. I > don't think we can really ensure no collisions mapping from uuid -> > ec2_id deterministically, and I don't see a clear path forward when > we do get a collision. > > Vish > > On May 8, 2012, at 12:24 AM, Michael Still wrote: > > > On 04/05/12 20:31, Eoghan Glynn wrote: > > > > Sorry for the slow reply, I've been trapped in meetings. > > > > [snip] > > > >> So the way things currently stand, the EC2 image ID isn't really > >> capable of > >> migration. > >> > >> I was thinking however that we should change the EC2 image > >> generation logic, > >> so that there is a reproducible glance UUID -> EC2 mapping (with a > >> small > >> chance of collision). This change would allow the same EC2 ID to > >> be generated > >> in multiple regions for a given glance UUID (modulo collisions). > >> > >> Would that be helpful in your migration use-case? > > > > I do think this is a good idea. Or even if the column wasn't > > auto-increment, but just picked a random number or something > > (because > > that would be marginally less likely to clash). Without somehow > > making > > these ec2 ids more global, replication between regions is going to > > suffer from ec2 api users having to somehow perform a lookup out of > > band. > > > > Now, my use case is a bit special, because I can enforce that > > images are > > only ever uploaded to one master region, and then copied to all > > others. > > I think that's probably not true for other users though. > > > > Mikal > > > > _______________________________________________ > > Mailing list: https://launchpad.net/~openstack > > Post to : openstack@lists.launchpad.net > > Unsubscribe : https://launchpad.net/~openstack > > More help : https://help.launchpad.net/ListHelp > > _______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : openstack@lists.launchpad.net Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp
