On Mon, Nov 18, 2013 at 5:18 PM, yunhong jiang < [email protected]> wrote:
> On Mon, 2013-11-18 at 15:32 -0800, Joe Gordon wrote: > > > > > > > > On Mon, Nov 18, 2013 at 4:08 PM, yunhong jiang > > <[email protected]> wrote: > > On Mon, 2013-11-18 at 14:09 -0800, Joe Gordon wrote: > > > > > > Phil Day discussed this at the summit and I have finally > > gotten around > > > to posting a POC of this. > > > > > > https://review.openstack.org/#/c/57053/ > > > > > > Hi, Joe, why you think the DB is not exact state in your > > followed commit > > message? I think the DB is updated to date by resource > > tracker, am I > > right (the resource tracker get the underlying resource > > information > > periodically but I think that information is mostly static). > > And I think > > the scheduler retry mainly comes from the race condition of > > multiple > > scheduler instance. > > > > > > > > > > You answered the question yourself, the compute nodes (indirectly) > > update the DB periodically, so the further you are from the last > > periodic update the less up to date the DB is. > > > But the compute node will also update the DB if any claim changes > between the period, and also considering currently the resource tracker > calculate the instance usage (like RAM, core etc) itself instead of > depends on hyper-visor report, I think the DB information should be > considered mostly up to date. > > Yes, *mostly* up to date I agree, we can just make that word 'mostly' configurable. Thanks for helping clarify this point. > Of course, I'm not against the information cache. > > --jyh > > > > Its there for both reasons. But yes it was originally put there > > because of the multi scheduler race condition. > > > > > > "We already have the concept that the DB isn't the exact state > > of the > > world, right now it's updated every 10 seconds. And we use the > > scheduler > > retry mechanism to handle cases where the scheduler was wrong. > > " > > > > > > _______________________________________________ > > OpenStack-dev mailing list > > [email protected] > > > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > > > > > > > _______________________________________________ > > OpenStack-dev mailing list > > [email protected] > > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > > > > _______________________________________________ > OpenStack-dev mailing list > [email protected] > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >
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