Posted	Nick	Remark
#openstack-nova - 2017-08-31
19:05:18	efried	And I'd have to have a separate one for every network.
19:05:29	efried	Okay; so how are qualitative attrs handled?
19:05:42	efried	Like, "give me a VGPU >= 10GHz"
19:05:52	dansmith	we don't do that
19:05:55	artom	Actually, in that situation, wouldn't the physical network become a resource, not a trait?
19:06:01	efried	sorry ^ quantitative
19:06:10	dansmith	efried: we don't do that :)
19:06:28	efried	Are we gonna?
19:06:50	dansmith	every time someone brings it up, jay has an aneurism
19:06:58	efried	Really? Cause he's the one who brought it up.
19:06:59	dansmith	it's too much complexity I think
19:07:02	dansmith	we have to model something
19:07:37	dansmith	so let's say you had some 5GHz and some 10GHz gpus
19:07:56	efried	Here's a jaypipes quote: "With the advent of the resource provider modeling, which includes an appropriate modeling of quantitative and qualitative things split out into resources (with inventory and allocation) and traits, we have a system that can (and IMHO should) be the basis for any future improvements to device management in Nova."
19:07:58	dansmith	you could have traits of gpu-5ghz on the 5ghz ones and gpu-5ghz and gpu-10ghz on the 10s
19:08:14	dansmith	efried: yep, totes
19:08:26	efried	dansmith So what did he mean by "quantitative"?
19:08:34	dansmith	efried: counts of resources
19:08:39	efried	oh.
19:08:40	dansmith	efried: counts of actual things
19:08:41	efried	Bugger.
19:08:56	dansmith	so my model above
19:09:09	dansmith	if you care about the fast one, you ask for a gpu-10ghz and you would weed out the 5s
19:09:25	efried	But if you want to set a minimum, you'll never get the 10s
19:09:37	dansmith	if you want at least 5, you would ask for that, and might get a 10 if that's how it falls
19:09:45	dansmith	I don't get that last statement
19:09:50	efried	Huh? How would that work?
19:10:00	dansmith	so,
19:10:19	efried	Placement doesn't know that "gpu-10ghz" is an okay thing to match to "gpu-5ghz"
19:10:19	dansmith	the 10g gpus has at-least-5g and at-leadt-10g traits attached
19:10:23	efried	It doesn't even know they're related
19:10:25	dansmith	right,
19:10:30	dansmith	which is why you put both traits on the 10s
19:10:33	efried	ohjeez
19:10:43	dansmith	and arrange your grammar in terms of traits
19:11:05	efried	okay, I reread your original statement, which I misread the first time.
19:11:47	artom	We need nested traits ;)
19:11:51	dansmith	the reason for doing this is that it's easy to model to everything
19:11:57	efried	"easy"
19:12:05	dansmith	compare this which is numerical to processor flags
19:12:15	dansmith	I can't say "give me a cpu with at least sse3"
19:12:36	efried	I don't know what that means
19:12:37	dansmith	because there were later procs without those things because they weren't the high-end one, but were faster, and had some other features that earlier ones didn't
19:12:53	dansmith	i.e. processor flags are not numerical, linear, and neat sets
19:13:06	efried	okay, right, I get that - those are qualitative measures. That's different.
19:13:15	efried	A proc either has that feature or it doesn't.
19:13:42	efried	I just don't see this model-quantity-as-quality thing scaling.
19:14:11	efried	What if I've got to deal with microversions or something.
19:14:26	dansmith	um, what?
19:15:10	efried	I don't want to have to tag my resource provider with version-at-least-1.1,version-at-least-1.2,version-at-least-1.3,version-at-least-1.4,...
19:15:54	dansmith	efried: so you want to add semver understandings to a request processor for things?
19:16:04	dansmith	is 1.4.3 > 1.3.7?
19:16:22	efried	yes it is; and yes, but not limited to semver.
19:16:29	dansmith	no it's not
19:16:47	dansmith	because I need a particular bug fix that was backported to 1.3.7 and 1.4.5
19:16:47	efried	1.4.3 isn't > 1.3.7 ?
19:16:55	dansmith	1.4.3 will not give me the bug fix, but you would choose it
19:17:24	dansmith	so then I need to say >= 1.3.7 || (! <1.4.6)
19:17:26	dansmith	or something
19:17:32	dansmith	and that gets crazy
19:17:47	dansmith	which is why boiling this down to abstract traits is useful
19:18:08	artom	What real resource would even have something like thing?
19:18:08	dansmith	it won't let you model everything down to the tiniest detail, but it's also something that people can grasp and can be reasonably generic
19:18:13	dansmith	artom: a hypervisor
19:18:18	artom	I understand clock speeds of various kinds of processors, but...
19:18:24	dansmith	artom: I assume that's where he was going
19:18:36	dansmith	and it's a common thing
19:18:49	dansmith	people need to be on at least hyperv 2012.4 in order to be able to use some fragile windows driver
19:19:17	dansmith	so instead of them needing to know versions, you can expose has-multiqueue-nics or something
19:19:27	efried	Yeah; I was trying to come up with an example of something that could have a lot of different quantitative traits where enumerating them becomes very unwieldy.
19:19:27	dansmith	and then if you have an older release with that fix backported, then that's all that matters
19:19:35	mriedem	bauzas: didn't you say that before 2.29 and the force flag on the evacuate API, that if you specified a host we'd bypass the scheduler, but now we only do it if you specify a host AND pass force=True?
19:19:40	dansmith	instead of needing to know the version semantics of the thing you're asking for
19:20:03	edleafe	dansmith: didn't we discuss trait comparisons like this a while ago, and concluded that anything beyond simple boolean "has trait" would be a unmanageable tangle of special comparison cases?
19:20:15	dansmith	edleafe: yes, precisely
19:20:45	efried	Spitballin here, but what I think I would like to see is a way for me to pass some part of the request spec down to the virt driver, who's responsible for understanding it in whatever manner it wants.
19:21:03	dansmith	efried: and that is precisely what we do not want you to be able to do
19:21:03	mriedem	bauzas: nvm, that's correct
19:21:09	artom	That would *definitely* not scale
19:21:10	dansmith	we have way too much of that shit today
19:21:14	dansmith	yeeeeah.
19:21:18	artom	Every boot request would go to every compute?
19:21:22	mriedem	if you pass 2.1 and host, force ends up being None in the API and we pass the host to conductor, which then bypasses the scheduler
19:21:34	efried	artom ohh, I see.
19:21:49	edleafe	Hey! Why don't we allow *extensions*? That'll solve all these problems!
19:22:03	efried	Way it's set up today, you can do the whole resource allocation business based on what the compute told you last time it checked in.
19:22:40	efried	...from a centralized spot (placement/scheduler)
19:22:58	dansmith	and don't forget multi-hypervisor clouds
19:23:12	dansmith	where much of the details aren't known until you get down to the compute, so if you couldn't pick the right one based on some generic properties,
19:23:21	dansmith	you get there and libvirt says "wtf is a hyperv 2012.4?"
19:23:28	dansmith	that's hugely wasteful
19:24:26	efried	So if I need to do something funkily virt-specific, I have to do it at get_inventory time.
19:24:37	efried	and setting-up-resource-providers time.
19:24:49	dansmith	you have to expose it as a generic count of resources with traits
19:24:56	efried	but constrained to ... yeah, what you said.
19:25:08	dansmith	because that's a model that the rest of nova can understand
19:25:10	artom	There was talk of doing virt driver capabilities as resources (or traits?), I think?
19:25:24	dansmith	yep, exactly his hypervisor version query
19:26:31	artom	Well, nova virt driver != hypervisor, but yeah, same gist
19:26:41	efried	Which is why we need nested resource providers: so my hypervisor can be an outermost one and tag itself with e.g. "CUSTOM_AIX_CAPABLE", and then everything else underneath that will inherit that trait?

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