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On 02/03/2014 12:28 PM, Khanh-Toan Tran wrote:

> Another though would be the need for Instance Group API [1].
> Currently users can only request multiple instances of the same
> flavors. These requests do not need LP to solve, just placing
> instances one by one is sufficient. Therefore we need this API so
> that users can request instances of different flavors, with some
> relations (constraints) among them. The advantage is that this logic
> and API will help us add Cinder volumes with ease (not sure how the
> Cinder-stackers think about it, though).

I don't think that the instance group API actually helps here.  (I think 
it's a good idea, just not directly related to this.)

I think what we really want is the ability to specify an arbitrary list 
of instances (or other things) that you want to schedule, each of which 
may have different image/flavor, each of which may be part of an 
instance group, a specific network, have metadata which associates with 
a host aggregate, desire specific PCI passthrough devices, etc.

An immediate user of something like this would be heat, since it would 
let them pass the whole stack to the scheduler in one API call.  The 
scheduler could then take a more holistic view, possibly doing a better 
fitting job than if the instances are scheduled one-at-a-time.

Chris