Open Stack

On 27/09/13 07:58, Mike Spreitzer wrote:
> I have begun to draft some specifics about the sorts of policies that
> might be added to infrastructure to inform a smart unified placement
> engine.  These are cast as an extension to Heat templates.  See
> https://wiki.openstack.org/wiki/Heat/PolicyExtension.  Comments solicited.

Maybe I'm missing something obvious, but I'm not convinced all that 
logic belongs in Heat.  I would expect nova and related components to 
expose grouping information (availability zones in nova, networks in 
quantum, etc) and for end users to supply the "group by" information.

In other words, when I want to create a stack, I would tell Heat that 
I'd like this stack in all zones or a subset of zones, and if I expect a 
specific subset of zones, I should have to name them.  I would not 
expect Heat to try to make smart placement decisions on my behalf.

I think that your use case for anti-collocation (which is a very good 
and important use case, don't get me wrong) is covered by using 
availability zones/cells/regions and so on as they are, and doesn't 
require much logic internal to Heat beyond obeying the constraint 
specified by a user.

Even LLMN Anti-Collocation can be reduced to nested stacks, where the 
inner stacks are anti-collocated across machines, the next level are 
anti-collocated across racks, and the top level across rooms (so long as 
the compute API exposes machines, racks and rooms to Heat - again, I 
don't think it's Heat's job to know about these).

Cheers,
-- 
Stephen Gran
Senior Systems Integrator - theguardian.com
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