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.
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
