openstack team mailing list archive

[Eoghan Glynn <eglynn@xxxxxxxxxx>]

BTW that patch is up for review as:

  https://review.openstack.org/7302

Cheers,
eoghan

> 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@xxxxxxxxxxxxxxxxxxx
> > > Unsubscribe : https://launchpad.net/~openstack
> > > More help   : https://help.launchpad.net/ListHelp
> > 
> > 
> 
> _______________________________________________
> Mailing list: https://launchpad.net/~openstack
> Post to     : openstack@xxxxxxxxxxxxxxxxxxx
> Unsubscribe : https://launchpad.net/~openstack
> More help   : https://help.launchpad.net/ListHelp
>