Open Stack

On 04/26/2014 09:41 PM, Jay Lau wrote:
> 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


While I personally like this sort of idea from the perspective of 
simplifying things for heat users, I see two problems.

First, my impression is that heat tries to provide a direct mapping of 
nova resources to heat resources.  Using a property of a heat resource 
to trigger the creation of a nova resource would not fit that model.

Second, it seems less well positioned for exposing possible server group 
enhancements in nova.  For example, one enhancement that has been 
discussed is to add a server group option to make the group scheduling 
policy a weighting factor if it can't be satisfied as a filter.  With 
the server group as an explicit resource there is a natural way to 
extend it.

Chris