[occi-wg] Link specification

[Csom Gyula]

Comments inline:)
________________________________________
Feladó: Ralf Nyren [ralf at nyren.net]
Küldve: 2010. szeptember 2. 10:35
Címzett: Csom Gyula; Edmonds, AndrewX; occi-wg at ogf.org
Tárgy: Re: [occi-wg] Link specification

On Thu, 02 Sep 2010 10:02:32 +0200, Csom Gyula <csom at interface.hu> wrote:

>> Take the following example:
>>
>> The user creates a new compute using some networks and disks, ie. define
>> links to some network
>> and disk. The compute is then deployed and soon becomes up and running.
>> Then later the user
>> deletes some network and disk... well, maybe she forgets about that they
>> are used within some
>> running compute. According to the implicit delete behaviour the computes
>> will "loose" its disks and
>> networks which might mean that it becomes unusable.

> I would say this is really up to the server implementation. Any kind of
> server implementation should disallow users from putting part of the
> system in an unusable state.

> However, the specification will not enforce this. Different use cases will
> require different semantics and a server is allowed to refuse requests
> when needed.

Ok. This clarifies the situation. That is:

* when deleting target resources the default behaviour is to automatically delete 
   links (pointing to them) as well. However
* a specific OCCI implementation might enforce its special policies before deleting 
   target resources.

Is that correct?:)

>> I think deleting source resources with links is a natural behaviour
>> since links are in fact "owned"
>> by the sources. However this might not be the case with target
>> resources, hence alternatives
>> might be examined as well - like:

> So if I have a Compute linked by a IPAddressLink to a Network, removing
> the IPAddressLink would also remove the Compute? That would be sure to
> upset the users... ;)

Ops, no:) What I tried to mean is the following. Taking your example: if I have a 
Compute (the source) linked by an IPAddressLink (the link) to a Network (the target) 
then 

* when deleting the Compute (the source) it is natural that the IPAddressLink (the
   link) is deleted automatically as well, since the network link (which in fact represents 
   a NIC) is "owned" by the compute. However
* when deleting the Network (the target) it might not be natural to delete the
   IPAddressLink as well, since the link (a NIC) is not "owned" by the network.

> No, the current model has it very nicely defined I think. And if you need
> any other (more sophisticated) lifecycle semantics, just subclass the
> Resourse/Link and implement whatever is needed.

Cheers,
Gyula