openstack team mailing list archive

[Joe Gordon <jogo@xxxxxxxxxxxxxxxx>]

Phil,

This may shine some light.

https://bugs.launchpad.net/nova/+bug/1016273

best,
Joe

On Fri, Jul 13, 2012 at 10:27 AM, Day, Phil <philip.day@xxxxxx> wrote:

> Hi Jay,
>
> If I read it correctly that updates the "*_used"  values that show actual
> consumption, but what I was looking for is the updates to the allocated
> values (free_ram_mb / free_disk_gb ) that were added for schedulers that
> didn’t want to over commit.
>
> I remember some detailed discussion with Chris and Sandy about how best to
> implement this in the face of multiple schedulers, failing creates, etc,
> some of which involved the notification systems.
>
> Brian Elliot pointed me to where in the fliter scheduler just recalculates
> these values from the instance table - so I guess the plans to maintain the
>  info in the Database were dropped along the way.
>
> Cheers,
> Phil
>
> -----Original Message-----
> From: openstack-bounces+philip.day=hp.com@xxxxxxxxxxxxxxxxxxx [mailto:
> openstack-bounces+philip.day=hp.com@xxxxxxxxxxxxxxxxxxx] On Behalf Of Jay
> Pipes
> Sent: 13 July 2012 17:36
> To: openstack@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Openstack] Capacity based scheduling: What updated
> free_ram_mb in Folsom
>
> Hi Phil,
>
> The nova.db.api.compute_node_update() call is what the individual virt
> drivers call to update the compute node stats. grep for that and you'll see
> where the calls to set the compute node data are called.
>
> Best,
> -jay
>
> On 07/13/2012 09:38 AM, Day, Phil wrote:
> > Hi Folks,
> >
> >
> >
> > I was reviewing a code change to add generic retries for build
> > failures ( https://review.openstack.org/#/c/9540/2 ), and wanted to be
> > sure that it wouldn’t invalidate the capacity accounting used by the
> scheduler.
> >
> >
> >
> > However I've been sitting here for a while working through the Folsom
> > scheduler code trying to understand how the capacity based scheduling
> > now works, and I’m sure I’m missing something obvious but I just can’t
> > work out where the free_ram_mb value in the compute_node table gets
> updated.
> >
> >
> >
> > I can see the database api method to update the values,
> > compute_node_utilization_update(),  it doesn’t look as if anything in
> > the code ever calls that ?
> >
> >
> >
> > From when I last looked at this / various discussions here and at the
> > design summits I thought the approach was that:
> >
> > -          The scheduler would make a call (rather than a cast) to the
> > compute manger, which would then do some verification work, update the
> > DB table whilst in the context of that call, and then start a thread
> > to complete the spawn.  The need to go all the way to the compute node
> > as a call was to avoid race conditions from multiple schedulers.  (the
> > change I’m looking at is part of a blueprint to avoid such a race, so
> > maybe I imagined the change from cast to call ?)
> >
> >
> >
> > -          On a delete, the capacity_notifer (which had to be configured
> > into the list_notifier) would detect the delete message, and decrement
> > the database values.
> >
> >
> >
> > But now I look through the code it looks as if the scheduler is still
> > doing a cast (scheduler/driver),  and although I can see the database
> > api call to update the values, compute_node_utilization_update(),  it
> > doesn’t look as if anything in the code ever calls that ?
> >
> >
> >
> > The ram_filter scheduler seems to use the free_ram_mb value, and that
> > value seems to come from the host_manager in the scheduler which is
> > read from the Database,  but I can't for the life of me work out where
> > these values are updated in the Database.
> >
> >
> >
> > The capacity_notifier, which used to decrement values on a VM deletion
> > only (according to the comments the increment was done in the
> > scheduler) seems to have now disappeared altogether in the move of the
> > notifier to openstack/common ?
> >
> >
> >
> > So I’m sure I’m missing some other even more cunning plan on how to
> > keep the values current, but I can’t for the life of me work out what
> > it is – can someone fill me in please ?
> >
> >
> >
> > Thanks,
> >
> > Phil
> >
> >
> >
> >
> >
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>
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