11:29 a.m.
----- Original Message -----
From: "Vered Volansky" <vered(a)redhat.com>
To: "Maor Lipchuk" <mlipchuk(a)redhat.com>, "Yair Zaslavsky"
<yzaslavs(a)redhat.com>, "Omer Frenkel"
<ofrenkel(a)redhat.com>, "Mike Kolesnik" <mkolesni(a)redhat.com>,
"Allon Mureinik" <amureini(a)redhat.com>, "Daniel Erez"
<derez(a)redhat.com>
Cc: engine-devel(a)ovirt.org
Sent: Tuesday, May 28, 2013 8:40:38 PM
Subject: Re: [Engine-devel] Disk BE very small refactoring
I had a problem, didn't see all the replies till now.
I'll add some more info as to why we want to do this like we do.
It all started from adding the readOnly property to disks. It should have
been handled like plugged is handled, yet plugged is a hack, and if we don't
change that now, we'll only keep on adding unreasonable hacks.
please explain why you think plugged is a hack? what is wrong with it?
So from the start -
Disk currently:
- Sometimes represents a disk in a vm context and sometimes not.
- Holds plugged property, which is only relevant when a disk is in a vm
context, which already suggests this is not the natural place for it.
- Also holds bootable and interface, which cause limitations of use, but are
not so obviously related to the relationship between Disk and Vm as plugged.
- Can be shared between several vm's, to some plugged and to some not
plugged.
- Will soon be optionally RO in one VM and RW in another, which is exactly
the same as plugged, and therefore plugged issue should be fixed first.
Every column in that shows a disk in the UI receives a Disk entity, and show
its contents, while plugged/unplugged is ignored when not in a VM context.
The way things are now, using a VmDevice in the where we need it to show plug
status, we'll also have to use it in all other columns, which is irrelevant
and just totally not related.
So using VmDevice in UI is a no go.
The UI is the main limitation forcing us to use something that extends Disk,
and what I described below is the easiest thing to implement in the time
restrictions we have without changing the entire system.
I think this answers all the questions not already answered by others.
Regarding Maor suggestion - might be a good idea, but not in this scope or
time-frame.
If there is any other/unanswered issue or objection to the design change
please share.
I appreciate your inputs,
Vered
sorry i didnt understand why the current disk object isnt good enough,
you get a disk, some of its properties are valid only in some situations.
i think its easier to use instead of couple of different objects representing the same
entity in different situations.
----- Original Message -----
> From: "Maor Lipchuk" <mlipchuk(a)redhat.com>
> To: "Vered Volansky" <vered(a)redhat.com>
> Cc: engine-devel(a)ovirt.org
> Sent: Tuesday, May 28, 2013 1:49:46 PM
> Subject: Re: [Engine-devel] Disk BE very small refactoring
>
> I think the main problem is that we abuse the business entity to act as
> an O/R mapping class to the DB and also to be used as a business entity
> for presentation purposes.
>
> I understand how Yair thought isPlugged could be fetched from vmDevice,
> this is a confusing design, and it is just one example and more to come.
>
> I suggest that if we already thinking of changing the class hierarchy,
> we can start by implementing a package for presentation classes for
> transient classes such as this instead enforcing complex hierarchy.
>
> The query class will fetch all the data from the DB and initialized the
> transient class and send it to the client.
> I think it could be a good start and will solve many issues we might
> encounter in the future.
>
> Regards,
> Maor
>
> On 05/28/2013 11:24 AM, Omer Frenkel wrote:
> >
> >
> > ----- Original Message -----
> >> From: "Yair Zaslavsky" <yzaslavs(a)redhat.com>
> >> To: "Vered Volansky" <vered(a)redhat.com>
> >> Cc: engine-devel(a)ovirt.org
> >> Sent: Monday, May 27, 2013 6:22:58 PM
> >> Subject: Re: [Engine-devel] Disk BE very small refactoring
> >>
> >> Vered,
> >> VmDevice has "isPlugged" field,
> >> Why not have somehow in your inheritence (either Disk or a subclass) a
> >> field
> >> : "VmDevice device"
> >
> > disk id is the device id, no need for field to represent the relation.
> > the combination of disk-id and a specific entity (vm/template) will get
> > you
> > the other info
> >
> >> and have isPlugged method called "device.isPlugged()" ?
> >>
> >> Then you can also add the readOnly property which is not represented at
> >> VmDevice.
> >>
> >>
> >> Does this sound logical to you?
> >>
> >> ----- Original Message -----
> >>> From: "Vered Volansky" <vered(a)redhat.com>
> >>> To: engine-devel(a)ovirt.org
> >>> Sent: Monday, May 27, 2013 6:18:58 PM
> >>> Subject: [Engine-devel] Disk BE very small refactoring
> >>>
> >>> Hi All,
> >>>
> >>> Please express your opinion if you have any -
> >>>
> >>> Currently Disk BE has a plugged property, which should be a property
of
> >>> the
> >>> relationship between vm(or template) and a disk.
> >>> I plan to remove this property from the Disk entity, and add new
> >>> entity,
> >>> called DeviceDisk.
> >>> This should inherit from Disk and contain the vm/template guid and the
> >>> plugged property at first round.
> >>> At second round it'll also contain the readOnly property, for RO
disks,
> >>> TBD
> >>> right after.
> >>>
> >>> Appreciate any input,
> >>> Vered
> >>> _______________________________________________
> >>> Engine-devel mailing list
> >>> Engine-devel(a)ovirt.org
> >>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> >>>
> >> _______________________________________________
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> >>
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>
>
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