I would just like to re-iterate that I think the entire UUID approach is flawed and issues like this are one of the key reasons why.
-George On Jul 8, 2011, at 7:02 AM, Soren Hansen wrote: > 2011/7/8 Ed Leafe <ed.le...@rackspace.com>: >> On Jul 7, 2011, at 11:46 AM, Trey Morris wrote: >>> If I had to choose between dropping or truncating UUIDs and failing feature >>> parity with the ec2 api, i'd go with the latter. Pros and cons for UUIDs >>> have already been discussed and decisions made. The EC2 api shouldn't get >>> in the way. A translation layer to sit in between the EC2 and OS APIs would >>> solve this issue without revisiting the UUID argument. >> The code to use the first 8 chars of the UUID in the ec2 id was created and >> working well, but discarded in favor of a more limited approach. > > Why? > >> The only issue was the increased likelihood of a duplicate ec2 id, as we'd >> be limited to only 4 billion of them or so. I thought that it would be >> fairly straightforward to add code to detect such dupes, and re-generate a >> new UUID for the instance in that event. > > How would that work? The frontend gets a reqeust for a new instance, > it sends it on to the backend that starts handling the request and > sends back the ID. What then? Either the backend would need to be > changed to wait for an "yes, I accept this UUID" from the frontend, > which is unfortunate, or the frontend would have to get the response > back, go "hm, this collides with an existing ID. Cancel the request, > and start over." In the latter case, a cost has already been incurred > by starting up and immediately shutting down the instance. > > Also, if instances had already been created through the OpenStack API > and were being queried through the EC2 API, there's no guarantee that > colliding ID's don't already exist. In that case, you need to figure > how to try to make sure that a request asking for that particular ID > always gives a response corresponding to the same actual instance. > This sounds crappy for a distributed system. If you want to perform > the collision check even for intances created through the OpenStack > API, then the reasons for choosing UUID's to begin with are moot. > > -- > Soren Hansen | http://linux2go.dk/ > Ubuntu Developer | http://www.ubuntu.com/ > OpenStack Developer | http://www.openstack.org/ > > _______________________________________________ > Mailing list: https://launchpad.net/~openstack > Post to : openstack@lists.launchpad.net > Unsubscribe : https://launchpad.net/~openstack > More help : https://help.launchpad.net/ListHelp -- George Reese - Chief Technology Officer, enStratus e: george.re...@enstratus.com t: @GeorgeReese p: +1.207.956.0217 f: +1.612.338.5041 enStratus: Governance for Public, Private, and Hybrid Clouds - @enStratus - http://www.enstratus.com To schedule a meeting with me: http://tungle.me/GeorgeReese
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