[Engine-devel] restapi - removing template from a specified storage-domain

[Ori Liel]

>
>
>----- Original Message -----
>From: "Itamar Heim" <iheim at redhat.com>
>To: "Omer Frenkel" <ofrenkel at redhat.com>
>Cc: "Ori Liel" <oliel at redhat.com>, engine-devel at ovirt.org, "Geert Jansen" <gjansen at redhat.com>
>Sent: Sunday, January 1, 2012 9:44:47 PM
>Subject: Re: [Engine-devel] restapi - removing template from a specified	storage-domain
>
>On 01/01/2012 05:59 PM, Omer Frenkel wrote:
>>
>>
>> ----- Original Message -----
>>> From: "Ori Liel"<oliel at redhat.com>
>>> To: engine-devel at ovirt.org
>>> Sent: Sunday, January 1, 2012 3:15:18 PM
>>> Subject: [Engine-devel] restapi - removing template from a specified	storage-domain
>>>
>>> I'm about to implement removing template from a specified
>>> storage-domain.
>>>
>>> A template is meta-data + disks. The meta-data is in the ovirt-engine
>>> database, the disks are (potentially) scattered across several
>>> storage-domains. Removing a template from a specified storage domain
>>> means removing that template's disks from that storage-domain.
>>> API-wise, it's better to enable the deletion at the single-disk
>>> level, otherwise rollback and all sorts of unnecessary complexities
>>> enter the picture. So what I would like to go forward with is the
>>> following API:
>>>
>>> DELETE /api/templates/{template_xxx}/disks/{disk_yyy}
>>>
>>>     <storage_domain id="domain_zzz"/>
>>>
>>> This means: "delete the disk 'disk_yyy' (which belongs to template
>>> 'template_xxx' from the storage-domain 'domain_zzz'.
>>>
>>> Any comments?
>>
>> just that CURRENT backend only allows removing per storage domain(s),
>> this functionallity is in plan, though (if that was what you meant..)
>
>I think the implementation for this can/should wait for the new support 
>in the backend if makes more sense api-wise, rather than implementing 
>based on the current limitations and later changing the api.
>the question is with the move to multiple storage domains, will an 
>atomic[1] verb to delete all disks from a specific storage domain (per 
>vm/template) will be provided, or only per disk.
>
>[1] well, delete is rollforward, so not sure i understand Ori's point 
>about rollback. OTOH, the API should probably behave the same for 
>move/copy of disks, etc.

What I meant by rollback issues is: how do we handle a scenario in which 
deletion of disk1 succeeds, but then deletion of disk2 fails? 

When you say 'delete is rollforward', I assume you mean that delete 
operations don't require roll-back, and that even if only partial deletion 
was done - that's ok (I'm verifying because I'm not familiar with the term 
roll-forward).

Assuming this is what you meant, I still prefer the per-disk deletion, 
because the scenario of partial success still requires extra handling: 

1) Backend would have to generate a complex message that disk1 was 
deleted but disk2 not. 

2) REST-API user might resend the same request to retry - and fail because
this time disk1 does not exist.