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Hi Mike,

Le 08/10/2013 08:51, Mike Spreitzer a écrit :
> On second thought, I should revise and extend my remarks.  This 
> message supersedes my previous two replies.
>
> Thanks.  I have a few questions.  First, I am a bit stymied by the 
> style of API documentation used in that document and many others: it 
> shows the first line of an HTTP request but says nothing about all the 
> other details.  I am sure some of those requests must have interesting 
> bodies, but I am not always sure which ones have a body at all, let 
> alone what goes in it.  I suspect there may be some headers that are 
> important too.  Am I missing something?
>
> That draft says the VMs are created before the group.  Is there a way 
> today to create a VM without scheduling it?  Is there a way to 
> activate a resource that has already been scheduled but not 
> activated?By "activate" I mean, for a VM instance for example, to 
> start running it.
>
> As I understand your draft, it lays out a three phase process for a 
> client to follow: create resources without scheduling or activating 
> them, then present the groups and policies to the service for joint 
> scheduling, then activate the resources.  With regard to a given 
> resource, things must happen in that order; between resources there is 
> a little more flexibility.  Activations are invoked by the client in 
> an order that is consistent with (a) runtime dependencies that are 
> mediated directly by the client (e.g., string slinging in the heat 
> engine) and (b) the nature of the resources (for example, you  can not 
> attach a volume to a VM instance until after both have been created). 
>  Other than those considerations, the ordering and/or parallelism is a 
> degree of freedom available to the client.  Have I got this right?
>
> Couldn't we simplify this into a two phase process: create groups and 
> resources with scheduling, then activate the resources in an 
> acceptable order?

I can't answer for it, but asfar as I can understand the draft, there is 
no clear understanding that we have topostpone the VM boot *after* 
creating the Groups.
As stated in the document, there is a strong prereqwhich is that all the 
resources mapped to the Group must have their own uuids, but there is no 
clear outstanding that it should prevent the VMs to actually boot.

At the moment, deferring a bootable state in Nova is not yet implemented 
and that's part of Climate folks to implement it, so I can't get your point.

-Sylvain

>
> FYI: my group is using Weaver as the software orchestration technique, 
> so there are no runtime dependencies that are mediated directly by the 
> client.  The client sees a very simple API: the client presents a 
> definition of all the groups and resources, and the service first 
> schedules it all then activates in an acceptable order.  (We already 
> have something in OpenStack that can do resource invocations in an 
> acceptable order, right?)  Weaver is not the only software 
> orchestration technique with this property.  The simplicity of this 
> API is one reason I recommend software orchestration techniques that 
> take dependency mediation out of the client's hands.  I hope that with 
> coming work on HOT we can get OpenStack to this level of API 
> simplicity.  But that struggle lies farther down the roadmap...
>
> I was wondering if you could explain why you included all those 
> integer IDs; aren't the UUIDs sufficient?  Do you intend that clients 
> will see/manipulate the integer IDs?
>
> If I understand your UML correctly, an InstanceGroup owns its metadata 
> but none of the other subsidiary objects introduced.  Why not?  If an 
> InstanceGroup is deleted, shouldn't all those other subsidiary objects 
> be deleted too?
>
> Thanks,
> Mike
>
> "Yathiraj Udupi (yudupi)" <yudupi at cisco.com> wrote on 10/07/2013 
> 11:10:20 PM:
> > Hi,
> >
> > Based on the discussions we have had in the past few scheduler sub-
> > team meetings,  I am sharing a document that proposes an updated
> > Instance Group Model and API extension model.
> > This is a work-in-progress draft version, but sharing it for early 
> feedback.
> > 
> https://docs.google.com/document/d/17OIiBoIavih-1y4zzK0oXyI66529f-7JTCVj-BcXURA/edit?usp=sharing
> >
> > This model support generic instance types, where an instance can
> > represent a virtual node of any resource type.  But in the context
> > of Nova, an instance refers to the VM instance.
> >
> > This builds on the existing proposal for Instance Group Extension as
> > documented here in this blueprint:  https://
> > blueprints.launchpad.net/nova/+spec/instance-group-api-extension
> >
> > Thanks,
> > Yathi.
> >
> >
>
>
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