On 10/23/2012 10:52 PM, Ayal Baron wrote:


----- Original Message -----
On Tue, Oct 23, 2012 at 05:53:20AM -0400, Doron Fediuck wrote:


----- Original Message -----
From: "Livnat Peer" <lp...@redhat.com>
To: "Dan Kenigsberg" <dan...@redhat.com>
Cc: engine-de...@ovirt.org, "Genadi Chereshnya"
<gcher...@redhat.com>, vdsm-de...@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" <yzasl...@redhat.com>
To: "Livnat Peer" <lp...@redhat.com>
Cc: "Genadi Chereshnya" <gcher...@redhat.com>,
engine-de...@ovirt.org, vdsm-de...@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" <lp...@redhat.com>
To: "Dan Kenigsberg" <dan...@redhat.com>
Cc: "Genadi Chereshnya" <gcher...@redhat.com>,
engine-de...@ovirt.org, vdsm-de...@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.

It's not hiding anything.
Today vdsm passes the libvirt xml to the hooks + the custom properties.
If you pass 'non-managed devices' through the devices API then basically you're 
saying to vdsm 'here is a bunch of things I want you to ignore but be a sport 
and pass it on to the hooks'.
Last I checked, that mechanism is custom properties.  I don't see any reason to 
add another one.

1. this means hooks don't actually get the unmanaged devices today?
2. custom property are to pass parameters to the hook user can reasonably control. device management should not be part of that if not strictly related to the hook (from user's side). 3. I'm guessing (didn't get this first time i read your answer), you are hinting the unmanaged devices should be passed as a custom property to vdsm, auto generated by engine?
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