[openstack-dev] [Heat] looking to add support for server groups to heat...any comments?

Mike Spreitzer mspreitz at us.ibm.com
Sun Apr 27 04:23:15 UTC 2014


Jay Lau <jay.lau.513 at gmail.com> wrote on 04/26/2014 11:41:25 PM:

> Just noticed this email, I have already filed a blueprint related to
> this topic https://blueprints.launchpad.net/heat/+spec/vm-instance-
> group-support

> My idea is that can we add a new field such as "PlacemenetPolicy" to
> AutoScalingGroup? If the value is affinity, then when heat engine 
> create the AutoScalingGroup, it will first create a server group 
> with affinity policy, then when create VM instance for the 
> AutoScalingGroup, heat engine will transfer the server group id as 
> scheduler hints so as to make sure all the VM instances in the 
> AutoScalingGroup can be created with affinity policy.
> 
> resources:
>   WorkloadGroup:
>     type: AWS::AutoScaling::AutoScalingGroup
>     properties:
>       AvailabilityZones: ["nova"]
>       LaunchConfigurationName: {Ref: LaunchConfig}
>       PlacementPolicy: ["affinity"] <<<<<<<<
>       MaxSize: 3
>       MinSize: 2

Remember that Heat has two resource types named 
<something>::<something>::AutoScalingGroup, plus OS::Heat::InstanceGroup, 
and also OS::Heat::ResourceGroup.  Two of those four kinds of group are 
almost (remember the indirection through ScaledResource) certainly groups 
of Compute instances; the other two are more open about their elements.  I 
think the thing you are clearly saying that might be new in this 
discussion is the proposal to make one or more of those four kinds of 
groups use Nova's server group feature.  The relevant kind of group would 
then gain all the properties, attributes, privileges, and responsibilities 
of a server group.  At least, that makes sense to me.  The biggest 
questions in my mind are which kinds of groups should get this treatment 
and how to cope with the cases where the element is NOT a Compute 
instance.  A sub-case of that last issue is: the scaled element is a 
composite thing that includes one or more Compute instances.

Regards,
Mike
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