[Engine-devel] [engine-devel] instance type as top-level entity

[Itamar Heim]

On 12/05/2013 09:40 AM, Tomas Jelinek wrote:
>
>
> ----- Original Message -----
>> From: "Itamar Heim" <iheim at redhat.com>
>> To: "Omer Frenkel" <ofrenkel at redhat.com>, "Tomas Jelinek" <tjelinek at redhat.com>
>> Cc: "engine-devel" <engine-devel at ovirt.org>
>> Sent: Wednesday, December 4, 2013 5:29:57 PM
>> Subject: Re: [Engine-devel] [engine-devel] instance type as top-level entity
>>
>> On 12/04/2013 02:17 PM, Omer Frenkel wrote:
>>>
>>>
>>> ----- Original Message -----
>>>> From: "Tomas Jelinek" <tjelinek at redhat.com>
>>>> To: "engine-devel" <engine-devel at ovirt.org>
>>>> Cc: "Omer Frenkel" <ofrenkel at redhat.com>
>>>> Sent: Wednesday, December 4, 2013 2:14:06 PM
>>>> Subject: [engine-devel] instance type as top-level entity
>>>>
>>>> Hey all,
>>>>
>>>> I have started to work on the instance types[1] again and hit an issue.
>>>> Since
>>>> the instance types are supposed to be top-level entities
>>>> (e.g. without the connection to DC/Cluster) but they are modeled as
>>>> templates
>>>> it is not possible to store them to DB since the DB constraints violation
>>>> on
>>>> vm_static table
>>>> (e.g. the vds_group_id has to be unique and point to an existing
>>>> vds_group).
>>>>
>>>> So, I see 4 options:
>>>>
>>>> 1: drop the constraints on the vm_static.vds_group_id (the
>>>> vds_groups_vm_static constraint)
>>>>      (most simple approach but would open the door to some issues which are
>>>>      now
>>>>      guard on the DB level)
>>>>
>>>> 2: do the same magic [well, hacks :) ] as with the "blank" template which
>>>> is
>>>> in the same situation
>>>>      (not exactly a nice solution to have the instance types wired to one
>>>>      specific cluster just to satisfy the constraint but return them all
>>>>      the
>>>>      time)
>>>>
>>>> 3: do not store this data in vm_static but create some new table called
>>>> e.g.
>>>> instance_type which would contain all of the fields from vm_static which
>>>> are
>>>> needed by it
>>>>      (actually the best approach AFAIK but to do it correctly it would
>>>>      require
>>>>      some more refactoring to do some hierarchy of tables and not copy the
>>>>      fields from table to table)
>>>>
>>>> 4: make the instance types not top-level (e.g. bound to specific
>>>> DC/Cluster)
>>>>      (would bring some issues for example with the default instance types
>>>>      which
>>>>      should be present for all the DC/Clusters)
>>>>
>>>> Thoughts?
>>>>
>>>> Thank you,
>>>> Tomas
>>>>
>>>> [1]: http://www.ovirt.org/Features/Instance_Types
>>>>
>>>
>>> according to the wiki (and discussions we had) instance type is bounded to
>>> a cluster (even if only as a changeable default)
>>> so i dont think there is an issue..
>>
>> where in the wiki please?
>> the way i read the wiki its DC level, just like templates?
>
> OK, it seems I have not asked the question correctly. Let me rephrase it:
> Since we are going to provide default (predefined) instance types which the user is not allowed to delete I assume this instance types should
> be available for the whole system (not only for the default cluster) just like blank template.

I think it makes sense to allow instance type (both default and custom 
ones) at system level. would be nice to allow them at cluster level as 
well of course.

>
> This brings up a question if all the other instance types are going to be also system level and if yes, how are we going to solve it technically.
> We still have the option to implement the instance types as templates and the default instance types as blank template, but the question is if this is
> what makes most sense.

if anything, i think everyone would appreciate if we remove the relation 
of Blank template to the default cluster so they can delete the default 
cluster...

>
> The wiki currently says that the instance type is connected to cluster using vds_group_id field but as I have started some implementation this
> question popped up in my mind (not yet documented on wiki - will be according to the result of this discussion).

it does say so, but i think you are right and we should allow system 
level as well. cc-ing andrew who authored this page for his thoughts?

>
> BTW the question if the instance types are top level or not leads us to a different question - where to put them in GUI?
> - If the instance type is a top level entity the best place to have it is the configure dialog (top right corner)
> - If the instance type is not a top level entity the best place to have it is possibly a main tab (or part of the template main tab)

well, the question is should we allow only system level (then configure 
is appropriate), or both system and cluster level, in which case a sub 
tab is more appropriate.

i could live with:
- only allow to configure instance types via configure (since its a
   rare operation, like configuring a role is).
- allow to set default enable/disable for an instance type.
- allow to set enable/disable override at cluster level, in which case,
    a subtab or a dialog at cluster level would do.

as a side note, i think 'configure' dialogs should be moved from the 
configure button to a new tree node, and appear as tab panes when 
standing on this new configure node in the tree.
>
>
>>
>>