[openstack-dev] [ironic] ironic and traits
Eric Fried
openstack at fried.cc
Mon Oct 23 14:09:22 UTC 2017
We discussed this a little bit further in IRC [1]. We're all in
agreement, but it's worth being precise on a couple of points:
* We're distinguishing between a "feature" and the "trait" that
represents it in placement. For the sake of this discussion, a
"feature" can (maybe) be switched on or off, but a "trait" can either be
present or absent on a RP.
* It matters *who* can turn a feature on/off.
* If it can be done by virt at spawn time, then it makes sense to have
the trait on the RP, and you can switch the feature on/off via a
separate extra_spec.
* But if it's e.g. an admin action, and spawn has no control, then the
trait needs to be *added* whenever the feature is *on*, and *removed*
whenever the feature is *off*.
[1]
http://eavesdrop.openstack.org/irclogs/%23openstack-nova/%23openstack-nova.2017-10-23.log.html#t2017-10-23T13:12:13
On 10/23/2017 08:15 AM, Sylvain Bauza wrote:
>
>
> On Mon, Oct 23, 2017 at 2:54 PM, Eric Fried <openstack at fried.cc
> <mailto:openstack at fried.cc>> wrote:
>
> I agree with Sean. In general terms:
>
> * A resource provider should be marked with a trait if that feature
> * Can be turned on or off (whether it's currently on or not); or
> * Is always on and can't ever be turned off.
>
>
> No, traits are not boolean. If a resource provider stops providing a
> capability, then the existing related trait should just be removed,
> that's it.
> If you see a trait, that's just means that the related capability for
> the Resource Provider is supported, that's it too.
>
> MHO.
>
> -Sylvain
>
>
>
> * A consumer wanting that feature present (doesn't matter whether it's
> on or off) should specify it as a required *trait*.
> * A consumer wanting that feature present and turned on should
> * Specify it as a required trait; AND
> * Indicate that it be turned on via some other mechanism (e.g. a
> separate extra_spec).
>
> I believe this satisfies Dmitry's (Ironic's) needs, but also Jay's drive
> for placement purity.
>
> Please invite me to the hangout or whatever.
>
> Thanks,
> Eric
>
> On 10/23/2017 07:22 AM, Mooney, Sean K wrote:
> >
> >
> >
> >
> > *From:*Jay Pipes [mailto:jaypipes at gmail.com
> <mailto:jaypipes at gmail.com>]
> > *Sent:* Monday, October 23, 2017 12:20 PM
> > *To:* OpenStack Development Mailing List
> <openstack-dev at lists.openstack.org
> <mailto:openstack-dev at lists.openstack.org>>
> > *Subject:* Re: [openstack-dev] [ironic] ironic and traits
> >
> >
> >
> > Writing from my phone... May I ask that before you proceed with any plan
> > that uses traits for state information that we have a hangout or
> > videoconference to discuss this? Unfortunately today and tomorrow I'm
> > not able to do a hangout but I can do one on Wednesday any time of the day.
> >
> >
> >
> > */[Mooney, Sean K] on the uefi boot topic I did bring up at the
> ptg that
> > we wanted to standardizes tratis for “verified boot” /*
> >
> > */that included a trait for uefi secure boot enabled and to
> indicated a
> > hardware root of trust, e.g. intel boot guard or similar/*
> >
> > */we distinctly wanted to be able to tag nova compute hosts with those
> > new traits so we could require that vms that request/*
> >
> > */a host with uefi secure boot enabled and a hardware root of
> trust are
> > scheduled only to those nodes. /*
> >
> > */ /*
> >
> > */There are many other examples that effect both vms and bare
> metal such
> > as, ecc/interleaved memory, cluster on die, /*
> >
> > */l3 cache code and data prioritization, vt-d/vt-c, HPET, Hyper
> > threading, power states … all of these feature may be present on the
> > platform/*
> >
> > */but I also need to know if they are turned on. Ruling out state in
> > traits means all of this logic will eventually get pushed to scheduler
> > filters/*
> >
> > */which will be suboptimal long term as more state is tracked.
> Software
> > defined infrastructure may be the future but hardware defined
> software/*
> >
> > */is sadly the present…/*
> >
> > */ /*
> >
> > */I do however think there should be a sperateion between asking for a
> > host that provides x with a trait and asking for x to be
> configure via/*
> >
> > */A trait. The trait secure_boot_enabled should never result in the
> > feature being enabled It should just find a host with it on. If
> you want/*
> >
> > */To request it to be turned on you would request a host with
> > secure_boot_capable as a trait and have a flavor extra spec or image
> > property to request/*
> >
> > */Ironic to enabled it. these are two very different request and
> should
> > not be treated the same. /*
> >
> >
> >
> >
> >
> > Lemme know!
> >
> > -jay
> >
> >
> >
> > On Oct 23, 2017 5:01 AM, "Dmitry Tantsur" <dtantsur at redhat.com <mailto:dtantsur at redhat.com>
> > <mailto:dtantsur at redhat.com <mailto:dtantsur at redhat.com>>> wrote:
> >
> > Hi Jay!
> >
> > I appreciate your comments, but I think you're approaching the
> > problem from purely VM point of view. Things simply don't work the
> > same way in bare metal, at least not if we want to provide the same
> > user experience.
> >
> >
> >
> > On Sun, Oct 22, 2017 at 2:25 PM, Jay Pipes <jaypipes at gmail.com <mailto:jaypipes at gmail.com>
> > <mailto:jaypipes at gmail.com <mailto:jaypipes at gmail.com>>> wrote:
> >
> > Sorry for delay, took a week off before starting a new job.
> > Comments inline.
> >
> > On 10/16/2017 12:24 PM, Dmitry Tantsur wrote:
> >
> > Hi all,
> >
> > I promised John to dump my thoughts on traits to the
> ML, so
> > here we go :)
> >
> > I see two roles of traits (or kinds of traits) for
> bare metal:
> > 1. traits that say what the node can do already (e.g. "the
> > node is
> > doing UEFI boot")
> > 2. traits that say what the node can be *configured* to do
> > (e.g. "the node can
> > boot in UEFI mode")
> >
> >
> > There's only one role for traits. #2 above. #1 is state
> > information. Traits are not for state information. Traits are
> > only for communicating capabilities of a resource provider
> > (baremetal node).
> >
> >
> >
> > These are not different, that's what I'm talking about here. No
> > users care about the difference between "this node was put in UEFI
> > mode by an operator in advance", "this node was put in UEFI
> mode by
> > an ironic driver on demand" and "this node is always in UEFI mode,
> > because it's AARCH64 and it does not have BIOS". These situation
> > produce the same result (the node is booted in UEFI mode), and
> thus
> > it's up to ironic to hide this difference.
> >
> >
> >
> > My suggestion with traits is one way to do it, I'm not sure
> what you
> > suggest though.
> >
> >
> >
> >
> > For example, let's say we add the following to the os-traits
> > library [1]
> >
> > * STORAGE_RAID_0
> > * STORAGE_RAID_1
> > * STORAGE_RAID_5
> > * STORAGE_RAID_6
> > * STORAGE_RAID_10
> >
> > The Ironic administrator would add all RAID-related traits to
> > the baremetal nodes that had the *capability* of
> supporting that
> > particular RAID setup [2]
> >
> > When provisioned, the baremetal node would either have RAID
> > configured in a certain level or not configured at all.
> >
> >
> > A very important note: the Placement API and Nova
> scheduler (or
> > future Ironic scheduler) doesn't care about this. At all.
> I know
> > it sounds like I'm being callous, but I'm not. Placement and
> > scheduling doesn't care about the state of things. It only
> cares
> > about the capabilities of target destinations. That's it.
> >
> >
> >
> > Yes, because VMs always start with a clean state, and
> hypervisor is
> > there to ensure that. We don't have this luxury in ironic :) E.g.
> > our SNMP driver is not even aware of boot modes (or RAID, or BIOS
> > configuration), which does not mean that a node using it cannot be
> > in UEFI mode (have a RAID or BIOS pre-configured, etc, etc).
> >
> >
> >
> >
> >
> > This seems confusing, but it's actually very useful.
> Say, I
> > have a flavor that
> > requests UEFI boot via a trait. It will match both the
> nodes
> > that are already in
> > UEFI mode, as well as nodes that can be put in UEFI mode.
> >
> >
> > No :) It will only match nodes that have the UEFI capability.
> > The set of providers that have the ability to be booted
> via UEFI
> > is *always* a superset of the set of providers that *have been
> > booted via UEFI*. Placement and scheduling decisions only care
> > about that superset -- the providers with a particular
> capability.
> >
> >
> >
> > Well, no, it will. Again, you're purely basing on the VM idea,
> where
> > a VM is always *put* in UEFI mode, no matter how the hypervisor
> > looks like. It is simply not the case for us. You have to care
> what
> > state the node is, because many drivers cannot change this state.
> >
> >
> >
> >
> >
> > This idea goes further with deploy templates (new concept
> > we've been thinking
> > about). A flavor can request something like CUSTOM_RAID_5,
> > and it will match the
> > nodes that already have RAID 5, or, more
> interestingly, the
> > nodes on which we
> > can build RAID 5 before deployment. The UEFI example above
> > can be treated in a
> > similar way.
> >
> > This ends up with two sources of knowledge about traits in
> > ironic:
> > 1. Operators setting something they know about hardware
> > ("this node is in UEFI
> > mode"),
> > 2. Ironic drivers reporting something they
> > 2.1. know about hardware ("this node is in UEFI mode" -
> > again)
> > 2.2. can do about hardware ("I can put this node in
> UEFI
> > mode")
> >
> >
> > You're correct that both pieces of information are important.
> > However, only the "can do about hardware" part is relevant to
> > Placement and Nova.
> >
> > For case #1 we are planning on a new CRUD API to set/unset
> > traits for a node.
> >
> >
> > I would *strongly* advise against this. Traits are not for
> state
> > information.
> >
> > Instead, consider having a DB (or JSON) schema that lists
> state
> > information in fields that are explicitly for that state
> > information.
> >
> > For example, a schema that looks like this:
> >
> > {
> > "boot": {
> > "mode": <one of 'bios' or 'uefi'>,
> > "params": <dict>
> > },
> > "disk": {
> > "raid": {
> > "level": <int>,
> > "controller": <one of 'sw' or 'hw'>,
> > "driver": <string>,
> > "params": <dict>
> > }, ...
> > },
> > "network": {
> > ...
> > }
> > }
> >
> > etc, etc.
> >
> > Don't use trait strings to represent state information.
> >
> >
> >
> > I don't see an alternative proposal that will satisfy what we have
> > to solve.
> >
> >
> >
> >
> > Best,
> > -jay
> >
> > Case #2 is more interesting. We have two options, I think:
> >
> > a) Operators still set traits on nodes, drivers are simply
> > validating them. E.g.
> > an operators sets CUSTOM_RAID_5, and the node's RAID
> > interface checks if it is
> > possible to do. The downside is obvious - with a lot of
> > deploy templates
> > available it can be a lot of manual work.
> >
> > b) Drivers report the traits, and they get somehow
> added to
> > the traits provided
> > by an operator. Technically, there are sub-cases again:
> > b.1) The new traits API returns a union of
> > operator-provided and
> > driver-provided traits
> > b.2) The new traits API returns only operator-provided
> > traits; driver-provided
> > traits are returned e.g. via a new field
> > (node.driver_traits). Then nova will
> > have to merge the lists itself.
> >
> > My personal favorite is the last option: I'd like a clear
> > distinction between
> > different "sources" of traits, but I'd also like to reduce
> > manual work for
> > operators.
> >
> > A valid counter-argument is: what if an operator wants to
> > override a
> > driver-provided trait? E.g. a node can do RAID 5, but I
> > don't want this
> > particular node to do it for any reason. I'm not sure if
> > it's a valid case, and
> > what to do about it.
> >
> > Let me know what you think.
> >
> > Dmitry
> >
> >
> > [1]
> http://git.openstack.org/cgit/openstack/os-traits/tree/
> <http://git.openstack.org/cgit/openstack/os-traits/tree/>
> > [2] Based on how many attached disks the node had, the
> presence
> > and abilities of a hardware RAID controller, etc
> >
> >
> >
> >
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