On 29 Jan 2025, at 21:30, Sean Mooney <smooney@redhat.com> wrote:

On 29/01/2025 19:54, Jan wrote:

On 1/29/25 19:45, Sean Mooney wrote:

On 29/01/2025 15:58, Jan wrote:

Hi,

is there a reason why some member variables of the nova instance
object are returned by the api and some not.

yes some are admin only and other are accessible to the member/reader role.

For example the "os_type" value is not returned but the "kernel_id"
(OS-EXT-SRV-ATTR:kernel_id) is.

os_type is not an atirbute of the instance its a properlty on the image.

How do you distinguish between image properties and attributes of an instance?

The os_type attribute is a field in the "Instance" class, and thus a column in the instance table in the nova database.

that is an artiface of the very early days of nova.

i belive it predates the intoduction of glance.


the instance os_type is now (for many years) an atribute of the root disk iamge

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the OS_TYPE is not a feild in the request you pass to nova to create the instance, it is populated form the image
if its set on the image.

in the past the xenAPI had a default_os_type config option which was also a vector to cofnigre it.

today the os_type can only be set via the os_type image property

i dont belive the OS_TYPE on the instance is actully used anymore for anything meaning full.

i think the only reaons we have not removed it si to avoid the upgrade impact of the db schema
contreaction and the fact that we can only remove it form the instance object on a major version bump
which is a lot of work for little gain.

There also exists an entry in the system_metadata table if os_type on an image was set. But os_type dependent settings, such as enabling of the hyperv feature emulation, depend only on the setting in the instance table.

we do not currently support showing the image proerties in general

kernel_id is diffent because when you create an instance you can
optionally specify an addtion kernl image to use.

i belive this can also be encoded as an image property but it can be
passed in the api request

so kernel_id is returned in server show because it can be passed as part
of the create request.

if you would like to be able to see the image properties like os_type in
the server show reponce you will be happy

to know that we are adding that this cycle
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that will bring parity with flavor extra specs.

I have a use case where it would be very helpful to get the "os_type"
via the api and python sdk.

Is there a chance that a patch implementing this would be accepted?

on its own no but it will be added by
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Thanks for the hint. I will definitely look into this.

this is the realted spec

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as i said instance do not have an os_type but the root disk image does
have one.

so you will be able to chekc the os_type in the image properties once
that is merged.

as this is an api change it will not be backportable.

Regards,
Jan