On Mon, 2014-03-17 at 12:39 -0700, Joe Gordon wrote: > On Mon, Mar 17, 2014 at 12:29 PM, Andrew Laski > <andrew.la...@rackspace.com> wrote: > On 03/17/14 at 01:11pm, Chris Friesen wrote: > On 03/17/2014 11:59 AM, John Garbutt wrote: > On 17 March 2014 17:54, John Garbutt > <j...@johngarbutt.com> wrote: > > Given the scheduler split, writing > that value into the nova db from > the scheduler would be a step > backwards, and it probably breaks lots > of code that assumes the host is not > set until much later. > > Why would that be a step backwards? The scheduler has > picked a host for the instance, so it seems reasonable > to record that information in the instance itself as > early as possible (to be incorporated into other > decision-making) rather than have it be implicit in > the destination of the next RPC message. > > Now I could believe that we have code that assumes > that having "instance.host" set implies that it's > already running on that host, but that's a different > issue. > > I forgot to mention, I am starting to be a fan > of a two-phase commit > approach, which could deal with these kinds of > things in a more > explicit way, before starting the main boot > process. > > Its not as elegant as a database transaction, > but that doesn't seems > possible in the log run, but there could well > be something I am > missing here too. > > I'm not an expert in this area, so I'm curious why you > think that database transactions wouldn't be possible > in the long run. > > > There has been some effort around splitting the scheduler out > of Nova and into its own project. So down the road the > scheduler may not have direct access to the Nova db. > > > If we do pull out the nova scheduler it can have its own DB, so I > don't think this should be an issue.
Just playing devil's advocate here, but even if Gantt had its own database, would that necessarily mean that there would be only a single database across the entire deployment? I'm thinking specifically in the case of cells, where presumably, scheduling requests would jump through multiple layers of Gantt services, would a single database transaction really be possible to effectively fence the entire scheduling request? Best, -jay _______________________________________________ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
