Re: [Engine-devel] alias in disk instead of name

23 Oct 2012

      ----- Original Message -----
...
From: "Charlie" <medievalist@gmail.com>
To: "Simon Grinberg" <simon@redhat.com>
Cc: "engine-devel" <engine-devel@ovirt.org>
Sent: Tuesday, October 23, 2012 6:51:35 PM
Subject: Re: [Engine-devel] alias in disk instead of name
OK, only because you asked...
Provide default unique names, so that users can just press enter if
names don't matter to them.  That way you obviate the entire
argument;
people who need special naming can have it, and everybody else has a
single extra keypress or mouseclick at naming time, and searching
works well enough.
You can name the first one vmdrive0 and increment the numeric part
each time a new drive is created.  Iterating until an unused name is
found isn't so computationally expensive that anyone should weep,
especially if you store the last used number and do an incrementing
sanity check against it at naming time.
Let's say the above solved all conflicts when coming to create a new disk, it does seems so.

Let's say that import/export if names conflict can be solved in a reasonable way - for example forcing (somehow and without bothering the user too much) a rename of the disk (How would you know if the conflicting name id auto-generated so can be replaced or user provided?, you'll have to resort to non-that-human-look-alike-name)

How does it solve the multi-tenancy use case?
I'm tenant A, setting up a quorum disk for my two VMs - so I call this disk simply quorum.
Now comes tenant B, he is also setting up a quorum disk, so he tries to call his disk quorum

But no,
He'll get a popup that this name is already taken - bad luck buddy.
Now he needs to guess the next available name? Would you build in algorithm to suggest alternatives?
Why should tenant B care in the first place that tenant A also wanted to call his disk 'quorum'?

Same with the VM name - but that is given for now, though I hope to convince it should change in the future.

What I'm trying to say here - infrastructure is for the admin - so you can force uniqueness
Resources like, disks and Virtual Machine belong to the end user thus you should let them determine their own names without being restricted by users of the system.
...
People expect names to have significance, and we like it when they
have both unique and non-unique parts.  It's part of our human
heritage.  Maybe whales and dolphins don't care.

...
--Charlie
On Tue, Oct 23, 2012 at 4:36 AM, Simon Grinberg <simon@redhat.com>
wrote:
...
We need more thoughts here from others, there are two different
approaches on the table and more opinions are welcomed.
If there are API consumers on this list then your view is more then
welcomed.
Thanks,
Simon.
----- Original Message -----
...
From: "Simon Grinberg" <simon@redhat.com>
To: "Michael Pasternak" <mpastern@redhat.com>
Cc: "engine-devel" <engine-devel@ovirt.org>
Sent: Monday, October 22, 2012 10:50:02 AM
Subject: Re: [Engine-devel] alias in disk instead of name
----- Original Message -----
...
From: "Michael Pasternak" <mpastern@redhat.com>
To: "Simon Grinberg" <simon@redhat.com>
Cc: "engine-devel" <engine-devel@ovirt.org>
Sent: Monday, October 22, 2012 8:58:25 AM
Subject: Re: [Engine-devel] alias in disk instead of name
On 10/21/2012 06:13 PM, Simon Grinberg wrote:
...
----- Original Message -----
...
From: "Michael Pasternak" <mpastern@redhat.com>
To: "Simon Grinberg" <simon@redhat.com>
Cc: "engine-devel" <engine-devel@ovirt.org>
Sent: Sunday, October 21, 2012 4:56:33 PM
Subject: Re: [Engine-devel] alias in disk instead of name
On 10/21/2012 04:15 PM, Simon Grinberg wrote:
>
>
> ----- Original Message -----
>> From: "Michael Pasternak" <mpastern@redhat.com>
>> To: "Simon Grinberg" <simon@redhat.com>
>> Cc: "engine-devel" <engine-devel@ovirt.org>
>> Sent: Sunday, October 21, 2012 3:48:46 PM
>> Subject: Re: [Engine-devel] alias in disk instead of name
>>
>> On 10/21/2012 03:36 PM, Simon Grinberg wrote:
>>>
>>> ----- Original Message -----
>>>>> From: "Michael Pasternak" <mpastern@redhat.com>
>>>>> To: "engine-devel" <engine-devel@ovirt.org>
>>>>> Sent: Sunday, October 21, 2012 12:26:46 PM
>>>>> Subject: [Engine-devel] alias in disk instead of name
>>>>>
>>>>>
>>>>> The problem we caused by using alias in disk instead of
>>>>> name
>>>>> is
>>>>> break
>>>>> of search-by-name paradigm
>>>>> in engine.search dialect, not sure why we do not want
>>>>> forcing
>>>>> disk
>>>>> name to be unique [1],
>>>>> but lack of "name" in disk search is does not look good
>>>>> in
>>>>> my
>>>>> view.
>>>>>
>>>>> thoughts?
>>>>>
>>>>> [1] can be easily achieved via appropriate can-do-action
>>>>> verification.
>>> Names by definition are not unique IDs,
>>
>> they do, otherwise /search wasn't effective, remember users
>> not
>> exposed to entity id, all entities fetched by-name, so
>> names
>> has
>> to
>> be unique.
>
> Yap that is what we do with many entities, and it causes
> problems.
> But with disks it is multiplied
>
>>
>>> thus it should not be enforced.
>>> What would be the auto naming conversion to ensure
>>> uniqueness
>>> with
>>> plain text?
>>
>> not sure i follow, i'll assume you refer here to empty
>> name, -
>> you
>> cannot have an
>> entity with no name.
>
> Well you create a new disk - do we want to enforce the user
> to
> provide a unique disk name/alias for every disk he creates?
> This will drive the user crazy. This is important even for
> user
> only for floating/shared disks. For any other disks user
> does
> not
> care if it's disk1, hd1, whatever. For these kind of disk,
> it's
> just a VM disk and the user does not care if in all VMs this
> is
> called disk 1 - so why bother him?
from the same reason we have unique
clusters/datacenters/networks/templates/etc...
Networks, DataCenter, Clusters, templates - are in order of
magnitude less then the number of disks.
And you name once and use many.
As for VMs - well it's may take that we should not force
uniqueness
either ( you can warn though )
you cannot have two vms with same name in same domain ...
I didn't say that in a domain you are allowed to have two guests
with
the same hostname, I've said engine should allow for having
duplicate VM names.
You are assuming that the VM name is identical to the guest host
name.
For many this is the case, for other it's just an alias/name given
in
oVirt.
Actually for the cloud, this is mostly going to be the case and
worse, you are blocking different tenants from having the same VM
name just because you are assuming that VM name = guest hostname.
...
...
For disks, well number is >= VMs to >>>= VMs
Name by definition is mostly interesting in many cases only
within
the VM, and we don't even have a way to correlate disk alias
to
the internal name in the VM. In many cases as said before, a
user
won't care about the name/alias if it is always attached to
the
same VM. A user will rather look the VM and then list it's
disk.
So actually I'll be better off with vm1.disk1 vm2.disk2 then
unique name per disk (PS AFAIK) this should be the default
suggested name by the UI, but then changing the VM name will
break
this (yes, I know it's not possible ATM, but many people I
know
requested for that).
So I as user will prefer that all the disks that created from
a
template will have the same name as the original template, and
then to be able to search by (vm=name, disk=name) thus I can
access easily the same disk for the VMs.
On the other hand for others, as you've mentioned (especially
for
floating and shared disk) the name/alias may be of importance,
uniqueness may be very important.
any disk can become shared.
Then when you make it shared then bother to give it a meaningful
alias
...
...
All that I'm saying that we can't force it's not that
uniqueness
in
never desired.
simon, you missing the point, i was talking about /search,
search is available only at /api/disks (i.e shared disks,
vm/template.disks is
irrelevant to this discussion)
Nope I do not, but I think that our perspectives differ.
You are looking at it as strictly design issue. You have a
collection
of entities and you want a human readable search, thus you are
trying to force (rightfully) from your point of view a unique
alias/name for those.
I taking the end user perspective, and user experience
1. Majority of the disks have no meaning outside of a VM scope.
2. There are fractions of the disks that are usually shared (this
is
the nature of shared disks)
3. There are fractions of floating, most of the floating will be a
transient state, while you are moving disks around.
What I'm trying to say that forcing a user to provide a unique
name
per disk is a huge bother.
And again in the multi tenancy case, you can't enforce a unique
alias
in the system.
What will you say to the user in the error message?
Sorry you can't use this alias since another user that is sharing
the
system with you already provided that name? And yes we know you
can't see that other disk, and it you don't care about the other
user, but still you can't use your alias since this is how our
platform designed.
The meaning is that you must allow a for a more sophisticated
search.
Yes even in the context of the disks tab. Disks are not really
stand
alone entities, and if we keep to strict conventions like - in any
collection an entity name must be unique, then you are making the
system hardly usable for many users.
So a search in disks should include other 'properties' (and yes I
know those are not disk properties, but this is how a user will
look
at it) like owner,quota,vm,storage domain, etc.
To some up - what should be unique are UUIDs of an entities, and
infrastructure entities names (within the same scope) - all the
rest
must not.
...
...
...
>
>>
>>> Would you change these on import/export?
>>
>> would you mind elaborating on this?
>
> Yes,
>
> You are already facing a problem when importing VMs that
> already
> have the same name, now you increasing the problem for disks
> that
> have the same alias. for same name we force clone if you
> want
> to
> import. Why for clone just because of a disk alias (this
> implies
> collapse snapshots ATM) or even bother the user with
> renaming
> disks that he does not care about the name so he just gave
> disk
> 1,
> 2, 3 and so on?
i see your point, but then we leave no option for the user to
locate
the disk,
simply because he doesn't have unique identifier,
just imagine user A creating disk and calling it X,
then user B creating disk and calling it X, they on different
domains etc., and now both want to use disk X,
how they can figure out which one to pick?, by SD, by size?
agree
this is doesn't look well..., even more than that - someone
may
call
this "bad design"...
This is why the search should accept more then the name.
Example (vm=name, disk=name/alias)
Example (dc=name, disk=name/alias)
Example (sd=name, disk=name/alias)
it's not about accepting both name/alias, it's about missing
ability
to identify your resource in collection.
...
For floating/shared on the same SD/DC/VM I would suggest a
warning
if there is a duplicate in the system - not enforcement.
ok, lets assume we WARN user that his disk's name is not unique,
how
user will pick the unique name?
implementing own code checking if new name (he wants to use) is
unique or not?
- this is business logic, not user's prerogative.
...
There is a difference between best practice and being
enforcing
up
to the level that it annoys some of the users.
simon, when you register to email, you have to try N times till
you
find unique username,
is it convenient? absolutely NO, is it annoying? YES, but you
forced
doing that so
system will be able to identify you,
it's no different in any way, good software protects user/itself
even
in cost of convenience,
bottom line
===========
- i think as long as disk not shared/floating it can have any
name
- in a minute disk designation changed to shared, name
uniqueness
should be forced (by the engine)
- when importing vm with shared disks, name uniqueness should be
forced
- when creating vm from template with shared disk, name
uniqueness
should be forced
- alias should be changed back to name (in sake of consistency)
- /api/disks collection should support searching disks by name
(in
sake of consistency)
thoughts?
Please look at the previous comment, that just can't work in the
multi-tenancy case.
Name should not be unique, the warning is for the admin only, from
the user portal a warning should be issues only if the user
provides
same name twice.
...
...
...
--
Michael Pasternak
RedHat, ENG-Virtualization R&D
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--
Michael Pasternak
RedHat, ENG-Virtualization R&D
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