Open Stack

On 27/09/13 14:27, Mike Spreitzer wrote:
> Stephen Gran <stephen.gran at theguardian.com> wrote on 09/27/2013 04:26:37 AM:

>  > 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.
>
> If there are five racks in the system and I want to say that two VMs
> should be placed on different racks, how do I say that with AZs without
> being overly specific?

If the admins of the openstack install wanted users to be able to select 
placement by rack, surely the availability zones would be rack1 - rack5 
?  In this case, the user would write:

   "Resources" : {
     "MyASG" : {
       "Type" : "AWS::AutoScaling::AutoScalingGroup",
       "Properties" : {
         "AvailabilityZones" : { "Fn::GetAZs" : ""},
         "MinSize" : "2",
	"DesiredSize": "2",
         "MaxSize" : "2",
       }
     },

This should naturally implement placement as spread evenly across AZs.

I think maybe this is where I think my disagreement is.  Heat should be 
able to express a user preference for placement, but only within the 
bounds of the policy already created by the admins of the nova install. 
  To have Heat have more knowledge than what is available via the nova 
API seems overcomplicated and fragile to me.  If the nova API should 
grow some extensions to make more complicated placement algorithms 
available, then that's an argument that might have legs.

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