[openstack-dev] [ironic] [nova] traits discussion call
Dmitry Tantsur
dtantsur at redhat.com
Tue Oct 24 16:00:13 UTC 2017
And the winner is Mon, 30 Oct, 2pm UTC!
The bluejeans ID is https://bluejeans.com/757528759
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On 10/23/2017 05:02 PM, Dmitry Tantsur wrote:
> 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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