[Openstack] [Heat] Autoscaling, scale VMs on different hosts

Deepthi Dharwar deepthi at linux.vnet.ibm.com
Fri Dec 5 10:43:49 UTC 2014

Hi all,

I have been using the autoscaling HOT template and have been successful
in running it. I do see number of VMs increasing and decreasing based on
my scaling metrics. However, I do have one extra requirement, i.e deploy
the VM on a different host.

The scenario being, if I have a VM1 running on a particular host1 and
when comes a need to  scale up based on the metrics, I want the new VM2
to be deployed on a different host i.e host2.

Scheduler does provide a filter i.e DifferentHostFilter, where one can
deploy an instance on a different host from a set of instances. However
to provide this as a part of scheduler hint in the HOT template, one
would need the UUID of previous spawned VM. Is there a way to get this
data via the HOT template and also pass it as different_host hint for
the new VM ?

So, if I have 2 hosts and have my webserver VM1 running on the host1,
ideally i would want VM2 webserver to be running on host2.
Is there an elegant way to achieve this ?

Please help!


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