[openstack-dev] [heat][ceilometer]: scale up/ down based on number of instances in a group

Daniel Comnea comnea.dani at gmail.com
Tue Oct 28 17:40:50 UTC 2014


Thanks all for reply.

I have spoke with Qiming and @Shardy (IRC nickname) and they confirmed this
is not possible as of today. Someone else - sorry i forgot his nicname on
IRC suggested to write a Ceilometer query to count the number of instances
but what @ZhiQiang said is true and this is what we have seen via the
instance sample

*@Clint - *that is the case indeed

*@ZhiQiang* - what do you mean by "*count of resource should be queried
from specific service's API*"? Is it related to Ceilometer's event types
configuration?

*@Mike - *my use case is very simple: i have a group of instances and in
case the # of instances reach the minimum number i set, i would like a new
instance to be spun up - think like a cluster where i want to maintain a
minimum number of members

With regards to the proposal you made -
https://review.openstack.org/#/c/127884/ that works but only in a specific
use case hence is not generic because the assumption is that my instances
are hooked behind a LBaaS which is not always the case.

Looking forward to see the 'convergence' in action.


Cheers,
Dani

On Tue, Oct 28, 2014 at 3:06 AM, Mike Spreitzer <mspreitz at us.ibm.com> wrote:

> Daniel Comnea <comnea.dani at gmail.com> wrote on 10/27/2014 07:16:32 AM:
>
> > Yes i did but if you look at this example
> >
> >
> https://github.com/openstack/heat-templates/blob/master/hot/autoscaling.yaml
> >
>
> > the flow is simple:
>
> > CPU alarm in Ceilometer triggers the "type: OS::Heat::ScalingPolicy"
> > which then triggers the "type: OS::Heat::AutoScalingGroup"
>
> Actually the ScalingPolicy does not "trigger" the ASG.  BTW,
> "ScalingPolicy" is mis-named; it is not a full policy, it is only an action
> (the condition part is missing --- as you noted, that is in the Ceilometer
> alarm).  The so-called ScalingPolicy does the action itself when
> triggered.  But it respects your configured min and max size.
>
> What are you concerned about making your scaling group smaller than your
> configured minimum?  Just checking here that there is not a
> misunderstanding.
>
> As Clint noted, there is a large-scale effort underway to make Heat
> maintain what it creates despite deletion of the underlying resources.
>
> There is also a small-scale effort underway to make ASGs recover from
> members stopping proper functioning for whatever reason.  See
> https://review.openstack.org/#/c/127884/ for a proposed interface and
> initial implementation.
>
> Regards,
> Mike
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