[openstack-dev] [Openstack-operators] [ironic] [nova] [tripleo] Deprecation of Nova's integration with Ironic Capabilities and ComputeCapabilitiesFilter

Jay Pipes jaypipes at gmail.com
Mon Oct 1 22:36:56 UTC 2018

On 10/01/2018 06:04 PM, Julia Kreger wrote:
> On Mon, Oct 1, 2018 at 2:41 PM Eric Fried <openstack at fried.cc> wrote:
>      > So say the user requests a node that supports UEFI because their
>     image
>      > needs UEFI. Which workflow would you want here?
>      >
>      > 1) The operator (or ironic?) has already configured the node to
>     boot in
>      > UEFI mode. Only pre-configured nodes advertise the "supports
>     UEFI" trait.
>      >
>      > 2) Any node that supports UEFI mode advertises the trait. Ironic
>     ensures
>      > that UEFI mode is enabled before provisioning the machine.
>      >
>      > I imagine doing #2 by passing the traits which were specifically
>      > requested by the user, from Nova to Ironic, so that Ironic can do the
>      > right thing for the user.
>      >
>      > Your proposal suggests that the user request the "supports UEFI"
>     trait,
>      > and *also* pass some glance UUID which the user understands will make
>      > sure the node actually boots in UEFI mode. Something like:
>      >
>      > openstack server create --flavor METAL_12CPU_128G --trait
>      > --config-data $TURN_ON_UEFI_UUID
>      >
>      > Note that I pass --trait because I hope that will one day be
>     supported
>      > and we can slow down the flavor explosion.
>     IMO --trait would be making things worse (but see below). I think UEFI
>     with Jay's model would be more like:
>        openstack server create --flavor METAL_12CPU_128G --config-data $UEFI
>     where the UEFI profile would be pretty trivial, consisting of
>     placement.traits.required = ["BOOT_MODE_UEFI"] and object.boot_mode =
>     "uefi".
>     I agree that this seems kind of heavy, and that it would be nice to be
>     able to say "boot mode is UEFI" just once. OTOH I get Jay's point that
>     we need to separate the placement decision from the instance
>     configuration.
>     That said, what if it was:
>       openstack config-profile create --name BOOT_MODE_UEFI --json -
>       {
>        "type": "boot_mode_scheme",
>        "version": 123,
>        "object": {
>            "boot_mode": "uefi"
>        },
>        "placement": {
>         "traits": {
>          "required": [
>           "BOOT_MODE_UEFI"
>          ]
>         }
>        }
>       }
>       ^D
>     And now you could in fact say
>       openstack server create --flavor foo --config-profile BOOT_MODE_UEFI
>     using the profile name, which happens to be the same as the trait name
>     because you made it so. Does that satisfy the yen for saying it once? (I
>     mean, despite the fact that you first had to say it three times to get
>     it set up.)
>     ========
>     I do want to zoom out a bit and point out that we're talking about
>     implementing a new framework of substantial size and impact when the
>     original proposal - using the trait for both - would just work out of
>     the box today with no changes in either API. Is it really worth it?
> +1000. Reading both of these threads, it feels like we're basically 
> trying to make something perfect. I think that is a fine goal, except it 
> is unrealistic because the enemy of good is perfection.
>     ========
>     By the way, with Jim's --trait suggestion, this:
>      > ...dozens of flavors that look like this:
>      > - 12CPU_128G_RAID10_DRIVE_LAYOUT_X
>      > - 12CPU_128G_RAID5_DRIVE_LAYOUT_X
>      > - 12CPU_128G_RAID01_DRIVE_LAYOUT_X
>      > - 12CPU_128G_RAID10_DRIVE_LAYOUT_Y
>      > - 12CPU_128G_RAID5_DRIVE_LAYOUT_Y
>      > - 12CPU_128G_RAID01_DRIVE_LAYOUT_Y
>     ...could actually become:
>       openstack server create --flavor 12CPU_128G --trait $WHICH_RAID
>     --trait
>     No flavor explosion.
> ++ I believe this was where this discussion kind of ended up in.. ?Dublin?
> The desire and discussion that led us into complex configuration 
> templates and profiles being submitted were for highly complex scenarios 
> where users wanted to assert detailed raid configurations to disk. 
> Naturally, there are many issues there. The ability to provide such 
> detail would be awesome for those 10% of operators that need such 
> functionality. Of course, if that is the only path forward, then we 
> delay the 90% from getting the minimum viable feature they need.
>     (Maybe if we called it something other than --trait, like maybe
>     --config-option, it would let us pretend we're not really overloading a
>     trait to do config - it's just a coincidence that the config option has
>     the same name as the trait it causes to be required.)
> I feel like it might be confusing, but totally +1 to matching required 
> trait name being a thing. That way scheduling is completely decoupled 
> and if everything was correct then the request should already be 
> scheduled properly.

I guess I'll just drop the idea of doing this properly then. It's true 
that the placement traits concept can be hacked up and the virt driver 
can just pass a list of trait strings to the Ironic API and that's the 
most expedient way to get what the 90% of people apparently want. It's 
also true that it will add a bunch of unmaintainable tribal knowledge 
into the interface between Nova and Ironic, but that has been the case 
for multiple years.

The flavor explosion problem will continue to get worse for those of us 
who deal with its pain (Oath in particular feels this) because the 
interface between nova flavors and Ironic instance capabilities will 
continue to be super-tightly-coupled.

For the record, I would have been happier if someone had proposed 
separating the instance configuration data in the flavor extra-specs 
from the notion of required placement constraints (i.e. traits). You 
could call the extra_spec "deploy_template_id" if you wanted and that 
extra spec value could have been passed to Ironic during node 
provisioning instead of the list of placement constraints (traits).

So, you'd have a list of actual placement traits for an instance that 
looked like this:


and you'd have a flavor extra spec called "deploy_template_id" with a 
value of the deploy template configuration data you wanted to 
communicate to Ironic. The Ironic virt driver could then just look for 
the "deploy_template_id" extra spec and pass the value of that to the 
Ironic API instead of passing a list of traits.

That would have at least satisfied my desire to separate configuration 
data from placement constraints.

Anyway, I'm done trying to please my own desires for a clean solution to 


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