[openstack-dev] [ironic] [nova] traits discussion call
Dmitry Tantsur
dtantsur at redhat.com
Mon Oct 23 15:02:58 UTC 2017
Hi all!
I'd like to invite you to the discussion of the way to implement traits in
ironic and the ironic virt driver. Please vote for the time at
https://doodle.com/poll/ts43k98kkvniv8uz. Please vote by EOD tomorrow.
Note that it's going to be a technical discussion - please make sure you
understand what traits are and why ironic cares about them. See below for more
context.
We'll probably use my bluejeans account, as it works without plugins in modern
browsers. I'll post a meeting ID when we pick the date.
On 10/23/2017 04:09 PM, Eric Fried wrote:
> 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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