7:02 a.m.
----- Original Message -----
From: "Dan Kenigsberg" <danken(a)redhat.com>
To: "Doron Fediuck" <dfediuck(a)redhat.com>
Cc: engine-devel(a)ovirt.org, vdsm-devel(a)fedorahosted.org, "Genadi Chereshnya"
<gcheresh(a)redhat.com>
Sent: Tuesday, October 23, 2012 1:41:03 PM
Subject: Re: [Engine-devel] [vdsm] unmanaged devices thrown into 'custom'
feature
On Tue, Oct 23, 2012 at 05:53:20AM -0400, Doron Fediuck wrote:
>
>
> ----- Original Message -----
> > From: "Livnat Peer" <lpeer(a)redhat.com>
> > To: "Dan Kenigsberg" <danken(a)redhat.com>
> > Cc: engine-devel(a)ovirt.org, "Genadi Chereshnya"
> > <gcheresh(a)redhat.com>, vdsm-devel(a)fedorahosted.org
> > Sent: Monday, October 22, 2012 8:29:20 AM
> > Subject: Re: [Engine-devel] [vdsm] unmanaged devices thrown into
> > 'custom' feature
> >
> > On 21/10/12 23:49, Dan Kenigsberg wrote:
> > > On Sun, Oct 21, 2012 at 11:57:10AM -0400, Eli Mesika wrote:
> > >>
> > >>
> > >> ----- Original Message -----
> > >>> From: "Yair Zaslavsky" <yzaslavs(a)redhat.com>
> > >>> To: "Livnat Peer" <lpeer(a)redhat.com>
> > >>> Cc: "Genadi Chereshnya" <gcheresh(a)redhat.com>,
> > >>> engine-devel(a)ovirt.org, vdsm-devel(a)fedorahosted.org
> > >>> Sent: Sunday, October 21, 2012 5:38:54 PM
> > >>> Subject: Re: [Engine-devel] unmanaged devices thrown into
> > >>> 'custom' feature
> > >>>
> > >>>
> > >>>
> > >>> ----- Original Message -----
> > >>>> From: "Livnat Peer" <lpeer(a)redhat.com>
> > >>>> To: "Dan Kenigsberg" <danken(a)redhat.com>
> > >>>> Cc: "Genadi Chereshnya"
<gcheresh(a)redhat.com>,
> > >>>> engine-devel(a)ovirt.org, vdsm-devel(a)fedorahosted.org
> > >>>> Sent: Sunday, October 21, 2012 5:18:31 PM
> > >>>> Subject: Re: [Engine-devel] unmanaged devices thrown into
> > >>>> 'custom'
> > >>>> feature
> > >>>>
> > >>>> On 21/10/12 16:42, Dan Kenigsberg wrote:
> > >>>>> I have just noticed that when a VM is started for the
> > >>>>> second
> > >>>>> time,
> > >>>>> Engine
> > >>>>> issues the "create" vdsm verb with some
information
> > >>>>> regarding
> > >>>>> "unmanaged" devices (an example is shown
below[1]) in the
> > >>>>> 'custom'
> > >>>>> propery bag.
> > >>>>>
> > >>>>> I'm surprised about this, as I was not aware of this
usage
> > >>>>> of
> > >>>>> the
> > >>>>> 'custom' dictionary, and Vdsm is not doing
anything with
> > >>>>> the
> > >>>>> data.
> > >>>>>
> > >>>>
> > >>>> If I recall correctly the idea of passing the unmanaged
> > >>>> devices
> > >>>> data
> > >>>> in
> > >>>> the custom property was to enable managing stable device
> > >>>> addresses
> > >>>> in
> > >>>> the hooks (to devices that were added to the VM via hooks
> > >>>> from
> > >>>> the
> > >>>> first
> > >>>> place), so this info is there not for VDSM use.
> > >>>> For example if you add a device in a hook it will be kept in
> > >>>> the
> > >>>> engine
> > >>>> as a non managed device. later when starting the VM again
> > >>>> you
> > >>>> would
> > >>>> like
> > >>>> to assign the same device address to your device, and you
> > >>>> can do
> > >>>> so
> > >>>> because you have access to the original address in the
> > >>>> custom
> > >>>> properties
> > >>>> of the VM.
> > >>>
> > >>> This is exactly what Eli has explained Gendai and Dan today.
> > >
> > > (I was asking here because I did not understand the verbal
> > > explanation.)
> > >
> > >>
> > >> This is taken from the Stable Device Address design in
> > >> http://wiki.ovirt.org/wiki/Features/Design/StableDeviceAddresses
> > >>
> > >> Unmanaged Device
> > >> -----------------
> > >> Unmanaged Device will be supported in the new format and will
> > >> include all unhandled devices as sound/controller/etc and
> > >> future
> > >> devices. Those devices will be persistent and will have Type ,
> > >> SubType (device specific) and an Address. For 3.1 an unmanaged
> > >> Device is not exposed to any GUI/REST API. Unmanaged devices
> > >> are
> > >> passed to vdsm inside a Custom property. VDSM in it turn is
> > >> passing this as is for possible hook processing.
> > >
> > > Thanks for the elaboration. Too bad that I've missed this issue
> > > before.
> > >
> > > Are you aware of any hook making use of this? I hope that hook
> > > writers
> > > are not using APIs that are not documented in vdsmd(8).
> > >
> > > It seems as a classic case where a generic bag interface is
> > > coerced
> > > into
> > > an awkward partially-documented interface.
> > >
> > > I think that a better approach would have been to pass all
> > > devices
> > > (managed and unmanaged alike) in the 'devices' property, and
> > > let
> > > vdsm
> > > expose whatever is needed to the before_vm_start hook.
> > >
> > > Maybe we can still do this.
> >
> > That was the original idea but Ayal objected and I think Igor did
> > not
> > like it as well...
> >
>
> +2.
> The original design had an 'unmanaged' (or generic) device type,
> and all
> devices should have been normalized. But as explained, this was
> strongly
> rejected in the VDSM side, causing Eli write some special handling
> for this anomaly.
Can someone (Ayal?) explain the rejection on Vdsm side?
Hiding part of the API in the custom propery bag requires strong
reasoning indeed.
I can't recall any rejection from my side
Dan.
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