[openstack-dev] [Heat] rough draft of Heat autoscaling API

Georgy Okrokvertskhov gokrokvertskhov at mirantis.com
Thu Nov 14 18:46:48 UTC 2013


It would be great if API specs contain a list of attributes\parameters one
can pass during group creation. I believe Zane already asked about
LaunchConfig, but I think new autoscaling API creation was specifically
designed to move from limited AWS ElasticLB to something with more broad
features. There is a BP I submitted while ago
We discussed it in IRC chat with heat team and we got to the conclusion
that this will be supported in new autoscaling API. Probably it is already
supported, but it is quite hard to figure this out from the existing API
specs without examples.


On Thu, Nov 14, 2013 at 9:56 AM, Zane Bitter <zbitter at redhat.com> wrote:

> On 14/11/13 17:19, Christopher Armstrong wrote:
>> http://docs.heatautoscale.apiary.io/
>> I've thrown together a rough sketch of the proposed API for autoscaling.
>> It's written in API-Blueprint format (which is a simple subset of
>> Markdown) and provides schemas for inputs and outputs using JSON-Schema.
>> The source document is currently atÂ
>> https://github.com/radix/heat/raw/as-api-spike/autoscaling.apibp
>> Things we still need to figure out:
>> - how to scope projects/domains. put them in the URL? get them from the
>> token?
>> - how webhooks are done (though this shouldn't affect the API too much;
>> they're basically just opaque)
> My 2c: the way I designed the Heat API was such that extant stacks can be
> addressed uniquely by name. Humans are pretty good with names, not so much
> with 128 bit numbers. The consequences of this for the design were:
>  - names must be unique per-tenant
>  - the tenant-id appears in the endpoint URL
> However, the rest of OpenStack seems to have gone in a direction where the
> "name" is really just a comment field, everything is addressed only by
> UUID. A consequence of this is that it renders the tenant-id in the URL
> pointless, so many projects are removing it.
> Unfortunately, one result is that if you create a resource and e.g. miss
> the Created response for any reason and thus do not have the UUID, there is
> now no safe, general automated way to delete it again. (There are obviously
> heuristics you could try.) To solve this problem, there is a proposal
> floating about for clients to provide another unique ID when making the
> request, which would render a retry of the request idempotent. That's
> insufficient, though, because if you decide to roll back instead of retry
> you still need a way to delete using only this ID.
> So basically, that design sucks for both humans (who have to remember
> UUIDs instead of names) and machines (Heat). However, it appears that I am
> in a minority of one on this point, so take it with a grain of salt.
>  Please read and comment :)
> A few comments...
> #1 thing is that the launch configuration needs to be somehow represented.
> In general we want the launch configuration to be a provider template, but
> we'll want to create a shortcut for the obvious case of just scaling
> servers. Maybe we pass a provider template (or URL) as well as parameters,
> and the former is optional.
> Successful creates should return 201 Created, not 200 OK.
> Responses from creates should include the UUID as well as the URI.
> (Getting into minor details here.)
> Policies are scoped within groups, so do they need a unique id or would a
> name do?
> I'm not sure I understand the webhooks part... webhook-exec is the thing
> that e.g. Ceilometer will use to signal an alarm, right? Why is it not
> called something like /groups/{group_id}/policies/{policy_id}/alarm ?
> (Maybe because it requires different auth middleware? Or does it?)
> And the other ones are setting up the notification actions? Can we call
> them notifications instead of webhooks? (After all, in the future we will
> probably want to add Marconi support, and maybe even Mistral support.) And
> why are these attached to the policy? Isn't the notification connected to
> changes in the group, rather than anything specific to the policy? Am I
> misunderstanding how this works? What is the difference between 'uri' and
> 'capability_uri'?
> You need to define PUT/PATCH methods for most of these also, obviously (I
> assume you just want to get this part nailed down first).
> cheers,
> Zane.
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Georgy Okrokvertskhov
Technical Program Manager,
Cloud and Infrastructure Services,
Tel. +1 650 963 9828
Mob. +1 650 996 3284
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