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On 10/14/2015 10:57 AM, Ben Nemec wrote:
> On 10/14/2015 06:38 AM, Dmitry Tantsur wrote:
>> Hi OoO'ers :)
>>
>> It's going to be a long letter, fasten your seat-belts (and excuse my 
>> bad, as usual, English)!
>>
>> In RDO Manager we used to have a feature called advanced profiles 
>> matching. It's still there in the documentation at 
>> http://docs.openstack.org/developer/tripleo-docs/advanced_deployment/profile_matching.html 
>> but the related code needed reworking and didn't quite make it upstream 
>> yet. This mail is an attempt to restart the discussion on this topic.
>>
>> Short explanation for those unaware of this feature: we used detailed 
>> data from introspection (acquired using hardware-detect utility [1]) to 
>> provide scheduling hints, which we called profiles. A profile is 
>> essentially a flavor, but calculated using much more data. E.g. you 
>> could sat that a profile "foo" will be assigned to nodes with 1024 <= 
>> RAM <= 4096 and with GPU devices present (an artificial example). 
>> Profile was put on an Ironic as a capability as a result of 
>> introspection. Please read the documentation linked above for more details.
>>
>> This feature had a bunch of problems with it, to name a few:
>> 1. It didn't have an API
>> 2. It required a user to modify files by hand to use it
>> 3. It was tied to a pretty specific syntax of the hardware [1] library
>>
>> So we decided to split this thing into 2 parts, which are of value one 
>> their own:
>>
>> 1. Pluggable introspection ramdisk - so that we don't force dependency 
>> on hardware-detect on everyone.
>> 2. User-defined introspection rules - some DSL that will allow a user to 
>> define something like a specs file (see link above) via an API. The 
>> outcome would be something, probably capabilit(y|ies) set on a node.
>> 3. Scheduler helper - an utility that will take capabilities set by the 
>> previous step, and turn them into exactly one profile to use.
>>
>> Long story short, we got 1 and 2 implemented in appropriate projects 
>> (ironic-python-agent and ironic-inspector) during the Liberty time 
>> frame. Now it's time to figure out what we do in TripleO about this, namely:
>>
>> 1. Do we need some standard way to define introspection rules for 
>> TripleO? E.g. a JSON file like we have for ironic nodes?
> 
> Yes, please.
> 
>>
>> 2. Do we need a scheduler helper at all? We could use only capabilities 
>> for scheduling, but then we can end up with the following situation: 
>> node1 has capabilities C1 and C2, node2 has capability C1. First we 
>> deploy a flavor with capability C1, it goes to node1. Then we deploy a 
>> flavor with capability C2 and it fails, despite us having 2 correct 
>> nodes initially. This is what state files were solving in [1] (again, 
>> please refer to the documentation).
> 
> It sounds like the answer is yes.  If the existing scheduler can't
> handle a valid use case then we need some sort of solution.
> 
>>
>> 3. If we need, where does it go? tripleo-common? Do we need an HTTP API 
>> for it, or do we just do it in place where we need it? After all, it's a 
>> pretty trivial manipulation with ironic nodes..
> 
> I think that would depend on what the helper ends up being.  I can't see
> it needing a REST API, but presumably it will have to plug into Nova
> somehow.  If it's something that would be generally useful (which it
> sounds like it might be - Ironic capabilities aren't a TripleO-specific
> thing), then it belongs in Nova itself IMHO.
> 
>>
>> 4. Finally, we need an option to tell introspection to use 
>> python-hardware. I don't think it should be on by default, but it will 
>> require rebuilding of IPA (due to a new dependency).
> 
> Can we not just build it in always, but only use it when desired?  Is
> the one extra dependency that much of a burden?

It pulls in python-numpy and python-pandas, which are pretty large.

> 
>>
>> Looking forward to your opinions.
>> Dmitry.
>>
>> [1] https://github.com/redhat-cip/hardware
>>
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> 
> 
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