[openstack-dev] Rackspace Plans Contributions to HEAT

Debojyoti Dutta ddutta at gmail.com
Thu Apr 4 19:23:33 UTC 2013

Sorry for the distraction, but there is a talk on recursive containers ...

Does HEAT do recursion? Community feedback would be awesome wrt if
recursion helps in deploying complex app topologies. Remember talking to
some folks after the Donabe talk during the Boston summit about recursion.
I guess HEAT was post BOSTON.


On Thu, Apr 4, 2013 at 11:53 AM, Robert Collins
<robertc at robertcollins.net>wrote:

> On 4 April 2013 18:37, Adrian Otto <adrian.otto at rackspace.com> wrote:
> > Alan,
> >
> > We want a useful Auto-Scale solution in Openstack, and recognize that
> Heat
> > has some capability already that could be leveraged. Whether Auto-Scale
> is
> > offered as a standalone service, by Heat, or (more likely) a combination
> of
> > both is open for discussion. Duncan's team is focused exclusively on
> > Auto-Scale, whereas our second team is concerned with the first three
> focus
> > areas I mentioned. So I will look to Duncan to gather input from you on
> > Auto-Scale.
> >
> > My take:
> >
> > Auto-scale is a control system. I believe that control systems should be
> > simple, and well coordinated. We should be careful not to end up with
> > multiple different control systems scattered about, especially in a
> complex
> > system like ours where the controls may actually conflict with each
> other.
> > Possible solutions include using centralized control, or perhaps well
> > coordinated federated control. Central control is simpler, so I prefer
> that
> > as a starting point. We could iterate toward something more elaborate as
> > needed.
> Agree with what you're saying here. I'd like to highlight one reason
> why I'm cautious about the idea of splitting autoscale out of heat.
> Consider rolling deployments with canaries: here you have (say) 1000
> machines running Swift-proxy, and you need to deploy a new image to
> them all. You start by deploying a small number (say 1), and check it
> runs ok; then 10, and check, then 100 and check - note that at this
> point 10% of your capacity is now deploying concurrently, or has
> deployed but isn't yet clearly ok. If you have a load spike at this
> point, it might be the *worst* possible thing would be to auto scale
> up, because the load spike might be due to a bad image/config in the
> new instances: adding more of the new image to the mix may just
> increase the problem.
> So autoscaling and deploys interact at a very deep level. What we need
> to do to deal with that is an open question, but one things seems
> clear - if Heat were to consume a separate auto scaling service, that
> service would have to either not make Nova calls itself (and just
> inform Heat as to recommended actions), or Heat would need to disable
> it during deployments, which is going to be a huge chunk of the time
> in busy environments.
> -Rob
> --
> Robert Collins <rbtcollins at hp.com>
> Distinguished Technologist
> HP Cloud Services
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