[openstack-dev] question about the scheduler filters

Michael J Fork mjfork at us.ibm.com
Fri Aug 17 14:42:52 UTC 2012


This is a great summary of the different Filters and their capabilities and
would be a great addition to the docs.  I had searched for this detail
before and ultimately ended up looking through code.  In particular, two
places:

http://docs.openstack.org/essex/openstack-compute/admin/content/scheduler-filters.html

http://docs.openstack.org/developer/nova/devref/filter_scheduler.html

On a similar thread, a one sentence summary of the filters in the docs
guide on the parent "Filters" page would be very helpful.

Michael

-------------------------------------------------
Michael Fork
Cloud Architect, Emerging Solutions
IBM Systems & Technology Group

Mark McLoughlin <markmc at redhat.com> wrote on 08/17/2012 07:42:17 AM:

> From: Mark McLoughlin <markmc at redhat.com>
> To: OpenStack Development Mailing List
<openstack-dev at lists.openstack.org>,
> Date: 08/17/2012 07:46 AM
> Subject: Re: [openstack-dev] question about the scheduler filters
>
> On Thu, 2012-08-16 at 20:22 -0600, Jim Fehlig wrote:
> > While merging the recent ComputeFilter additions with the ArchFilter, I
> > spent too much time agonizing over the name ArchFilter, which I was now
> > making filter on more than just architecture.
ComputeCapabilitiesFilter
> > seems like better name, but this is already taken.
> >
> > Looking at ComputeCapabilitiesFilter again, I realize it is filtering
on
> > some of the same properties as the combined ArchFilter [1], but from a
> > different source.  IIUC, ComputeCapabilitiesFilter filters on
properties
> > that originate from the instance type/flavor.  The combined ArchFilter
> > filters on properties that originate from the image.  It seems this
> > could be a source of confusion for users, but at the same time seems
> > necessary, particularly for properties such as architecture, preferred
> > hypervisor and virtual machine mode, which I tend to think are
> > properties of an image more so than a flavor.  E.g. I could select my
> > "Xen arm" flavor, but unless I also selected a "Xen arm" image, I could
> > have an instance that doesn't boot.
> >
> > Do folks have any issues with filters using both image and flavor
> > properties?  Being relatively new here, this may very well be intended
> > :).  If so, I'd like to change the name of ArchFilter to better reflect
> > its new additions.  What do you think of ImagePropertiesFilter?  It
> > filters hosts based on compute properties defined on the image.  Or
> > ImageComputePropertiesFilter, to accommodate a future class of
> > filterable image properties?
>
> Ok, stepping back for a minute. Before your patch, we had:
>
> ComputeFilter
>   simply matches enabled compute hosts
>
> ArchFilter
>   match the architecture from the image properties against the compute
>   node's permitted_instance_types
>
>   it's using instance_properties['architecture'] which is taken from the
>   image's architecture property in _create_instance() - see how
>   base_options is populated
>
>   permitted_instance_types is just the list of guest archs
>
> ComputeCapabilitiesFilter
>   matches properties defined in an instance type's extra specs against
>   compute capabilities
>
> AggregateInstanceExtraSpecsFilter
>   matches properties defined in an instance type's extra specs against
>   admin-defined properties on a host aggregate
>
> And then you added:
>
>   match the arch, hypervisor type and vm type from the image properties
>   against those supported by the compute node
>
> It looks to me like what you've added is a complete superset of
> ArchFilter - i.e. if you just specify the architecture property on the
> image, the behaviour should be identical.
>
> So, IMHO, it should be fine to move your new matching into
> ImagePropertiesFilter and just delete ArchFilter.
>
> Cheers,
> Mark.
>
>
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> OpenStack-dev at lists.openstack.org
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>
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