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#openstack-nova - 2017-04-26
16:52:48 cburgess mriedem I feel like we need a method that ensures a compute node can assert that it can never ever host a local disk.
16:52:58 mriedem and we can start listing the use cases and options, and pros/cons for each option
16:53:01 mgagne maybe just list the use cases, we don't need to agree on the validity of the need, just list them, list associated workaround/limitations, etc. and start from there
16:53:07 mriedem *then* put that in the ML for discussion
16:53:08 cburgess mriedem Yeah.. lets start with an etherpad. Once we get it to an ok state we can post it to the ML.
16:53:14 cburgess mriedem I like it.
16:53:27 cburgess mgagne Right.. only rule out the most obviously insane ideas.
16:53:39 mriedem mgagne: cburgess: i'll create an etherpad after the cells meeting and report back here
16:53:47 mgagne we can list them and explain later why we can't or don't want to support them
16:53:47 cburgess mriedem Rainbows
16:54:09 mgagne so people don't come back later and ask why that one isn't listed
16:54:38 mriedem looks like the etherpads have started https://wiki.openstack.org/wiki/Forum/Boston2017
16:54:43 mriedem which was on my todo list anyway
16:54:55 cburgess mgagne I'm only advocating ruling out things like "create a new top level openstack project" or other things of that level.
17:06:01 mordred cdent: what does placement use in the id field of its version doc?
17:08:37 cdent mordred: the min version
17:08:51 cdent which is a fudge
17:09:17 cdent it might make sense to split on '.' and use [0]
17:14:28 mordred cdent: ok. so it does have a value in id
17:14:48 cdent yeah, but it puts nothing in the url that indicates version and has no plan to
17:17:04 sumedhdegaonkar Hello all, this is my first review request, so please bear with me. I'd like to get your opinion/review of https://review.openstack.org/#/c/459794/ - It's just removing a restriction to use of 'sata' disk bus type for qemu and kvm. No change to default behavior or selection and hence in my opinion, no need to update test cases
17:30:18 openstackgerrit Rafael Folco proposed openstack/nova master: placement: Specific error for inventory in use https://review.openstack.org/460231
17:31:10 cdent mriedem: way back in earlier conversation you mentioned a bug in gabbi with left hand side json path substitutions. I meant to link you to this: https://github.com/cdent/gabbi/issues/170
17:31:30 cdent but also to ask: was that germane to what were talking about at the time, or just an observation?
17:32:15 mriedem it was related
17:32:23 mriedem i was also looking through the gabbits for an example of a response
17:32:24 mriedem to see the keys
17:33:37 cdent mriedem: I could fix that bug in the case you're talking about it is often easier to make the right hand side more complete (a structure instead of a string)
17:37:35 mriedem not a priority for me, i just noticed the comments in the gabbits about the limitation
17:37:43 mriedem api-ref is the priority,
17:37:49 mriedem because then i don't need to look at gabbits
17:38:23 cdent i regret slinging that name around
17:43:57 openstackgerrit Steven Webster proposed openstack/nova master: Improve comment for PCI port binding update https://review.openstack.org/460233
17:51:02 mriedem mgagne: cburgess: johnthetubaguy: stackempty: here you go https://etherpad.openstack.org/p/BOS-forum-using-cinder-for-nova-ephemeral-storage
17:51:47 cburgess mriedem Are we open to having a 'short term' and a 'long term' set of goals and solutions?
17:52:12 mriedem i think you could tag things that way
17:52:24 mriedem i'm open to eating lunch
17:52:27 mriedem so bbiab
17:55:39 openstackgerrit Lee Yarwood proposed openstack/nova master: libvirt: Attach and detach encryptors during swap_volume https://review.openstack.org/460244
17:55:39 openstackgerrit Lee Yarwood proposed openstack/nova master: libvirt: Refactor encryptor attach and detach calls https://review.openstack.org/460243
17:57:51 cburgess mriedem Just doing that myself
18:04:37 mgagne cburgess: so there are 2 use cases? : 1) Provide a default BDM 2) Prevent/forbid source=local in BDM
18:05:19 mgagne in fact, destination=local
18:06:38 dansmith does anyone know if test_delete_server_while_in_building_state is known to be flaky at the moment? logstash doesn't seem to think it's spiking but I see plenty of failures that aren't in my patch, like even on periodic stable jobs
18:06:40 dansmith mriedem: sdague ^
18:12:02 mgagne k policy.
18:12:02 mgagne cburgess: what do you think about the idea of having a "default bdm" for flavor-root-disk-none ? If you provide no BDM, the root_gb size is used to create a volume for you for your root disk. (flavor could also provide default volume type) This means no 400 HTTP error by default as a sane behavior/default is provided. An other extra spec or flavor attribute could forbid destination=local so if BDM is provided, it still respect the no-local-dis
18:12:46 cburgess mgagne Thats a decent idea. Pull size from root_gb and image_id from request spec.
18:12:52 mgagne yes
18:13:04 mgagne that's basically what we did on our side
18:13:44 mgagne also this could allow Horizon or dashboard to present appropriate UI (default to BFV view or something like that)
18:14:59 mgagne I also see 2 sub use cases: 1) flavor itself *never* support local disk. 2) specific compute nodes *never* want local disk. // One can be implemented without the other.
18:16:21 cburgess Right so #2 is my biggest concern and the biggest pain right now. Ensuring it can never happen. Because if it does happen you end up with data a user might care about living on a single local disk on a compute node, and thats very bad.
18:16:54 mgagne ok, can I take the liberty of splitting the use cases on etherpad?
18:17:02 cburgess mgagne Sure
18:17:33 openstackgerrit OpenStack Proposal Bot proposed openstack/os-vif master: Updated from global requirements https://review.openstack.org/451049
18:17:40 cburgess mgagne I prefer that actually as I think there are 2 orthogonal needs 1) Making BDM/cinder integration better, 2) Making sure we can block local disk.
18:17:51 mgagne yes
18:18:21 cburgess mgagne #2 we should focus on a 1-2 cycle solution, for #1 we should take a step back and say whats need to really do this right (aka the cinder imagebackend).
18:18:35 mgagne 100% agree
18:19:04 mgagne what about ephemeral disks or swap? what's your take?
18:19:23 cburgess Personally I love the idea of a cinder imagebackend but to do that right I think its going to require first rewritting the existing backends to have a much more modular and cleaner seperation.
18:20:08 mgagne yes, I found the task to be near impossible without major refactor when I checked years ago, hence the middleware hack
18:20:14 cburgess mgagne I don't understand the use case for either of those. Honestly I would vote to remove them from nova entirely but I know that wouldn't fly. The question is should we require all backends to support them or should we make those optional.
18:20:39 mordred mgagne, cburgess: in the name of requesting absurd features from people while the local vs. remote disk discussion is taking place ...
18:20:59 cburgess mgagne Right. We also have cases where things like instance_path are used both for the imagebackend and for non-imagebackend things like console logs, libvirt xml etc. So we have to get a clean separation there as well.
18:21:12 cburgess mordred Yes......?
18:21:16 mordred no-local-disk is really useful in both keeping data protected and making sure live migration can happen well ...
18:21:29 erhudy is the goal to eventually turn over all responsibility for block storage to cinder and remove it from nova entirely?
18:21:40 cburgess erhudy Thats is not my goal.
18:21:55 cburgess erhudy My goal is to provide an improved integration between nova and cinder.
18:22:07 mordred but depending on workload, the user might also know "this node is part of an application-level high availablity set, killing it and its data rather than live-migrating it is fine"
18:22:38 mordred especially when for those things locally attached things that behave like ephemeral disk does today is nice becaues of the lack of network latency hop between the vm and disk
18:22:59 mgagne cburgess: So having the ability to split imagebackend/disk from "hypervisor" (logs, xml) files is something an operator should be able to do?
18:23:10 cburgess mordred Hmm hand't thought about that. data volume on cinder, but a local ephemeral disk for "fast" scratch.
18:23:14 mordred yah
18:23:27 mordred but as a user opt-in sort fo thing
18:23:40 mordred since it's definitely a choice witha tradeoff involved
18:23:43 cburgess mgagne Well.. I think the only way to truely make imagebackend modular enough to support cinder we would have to have that clean seperation since cinder isn't going to provide us a way of storing that data.
18:23:45 erhudy cburgess: that can be done now
18:24:02 cburgess erhudy Which thing?
18:24:07 mgagne cburgess: that's the use case I can think of, like on SSD or NVMe
18:24:18 erhudy data/root volumes on cinder with local storage ephemeral disk
18:24:46 erhudy what i keep coming back to as part of our architecture discussions here is wanting to be able to do something like AWS instance store volumes, which afaik doesn't really have an analogue in nova
18:24:53 cburgess erhudy Yes I'm aware. mordred was pointing out that my state of "kill ephemeral in a fire" didn't take into acount that very valid use case.
18:25:07 mordred cburgess: the mirror.*.openstack.org farm is a good example- the only things on the local disk are cache - everything else is stored somewhere else
18:25:13 erhudy you can pass whatever you like to nova in the BDM but unless it matches your flavor it gets rejected
18:26:00 mordred but we'd be totally fine with the datain the ephemeral going away for those nodes, and could opt-in at boot to that and _maybe_ that makes something better for someone somewhere
18:26:30 mordred "hey, we actually don't find the stuff in X precious, DNR" :)
18:26:34 erhudy "ephemeral" in nova-ese is different from "ephemeral" in AWS-ese anyway, which confused a lot of our users
18:26:35 cburgess mordred right. Its def a valid use case. We should make it possible for a user to request a local disk as well *if* the compute node supports it.
18:26:41 mordred cburgess: ++
18:27:20 cburgess erhudy Its very confusing and something it would be good to clear up some as we think about what would be involved in "fixing" storage in nova.
18:27:23 mordred there are definitely places where we're using cinder volumes for things that are totally non-precious because it's the only way we can get our hands on the disk
18:27:51 mgagne cburgess: isn't this use case already supported? like have a flavor with local root + 1 ephemeral + 1 attached volume for your data.
18:28:01 erhudy sounds like the sort of dilemma where you can ask 10 people and get 11 answers
18:28:02 cburgess mordred We are seeing more and more client deploying there clouds that way. Some cinder integrated storage device and no local storage at all.
18:28:45 mordred cburgess: yah. I mean, in those cases we're fine using cinder- I just mostly don't want to stress out someone's storage backplane if there's cheaper/crappier disk available too
18:28:49 erhudy we are leaning that way in our current greenfield setup, doing it all on ceph, but we may keep nova local storage around for certain use cases
18:28:51 mordred for _some_ things

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