[Engine-devel] Hot-plug of disks and nics

[Ori Liel]

>
>
>----- Original Message -----
>From: "Ori Liel" <oliel at redhat.com>
>To: engine-devel at ovirt.org
>Cc: meyering at redhat.com, eglynn at redhat.com, gjansen at redhat.com, jhernand at redhat.com, "Einav Cohen" <ecohen at redhat.com>, "Roy Golan" <rgolan at redhat.com>, "Michael Kublin" <mkublin at redhat.com>
>Sent: Wednesday, April 11, 2012 11:32:51 AM
>Subject: Hot-plug of disks and nics
>
>On the subject of activate/deactivate disks and nics ("hot-plug"), I'd like to hear opinions about the correct modelling. I see two possible options (I will use disks as an example, but the chosen modelling should be the same for nics and disks). 
>
>Option 1 - update: 
>=================
>PUT
>.../api/vms/{vm:id}/disks/{disk:id}
><disk>
>  <activated>true</activated>
></disk>
>
>Pros: 
>-----
>* RESTful, no need for new action
>
>Cons: 
>-----
>* Inconsistent with other flows. We do not normally update status fields to perform actions. For example to run a VM, we do not update it's status to 'activated', we run an action (start). 
>* Enables user to update disk properties AND activate/deactivate in the same operation. Updating certain disk properties is forbidden while the VM is up, but activating/deactivating the disk is allowed always. This requires business-logic in REST-API: if the user activates the disk and changes properties on it - REST-API must first change the properties and then activate the disk (if disk is activated first, update properties will fail). If, on the other hand, the user *deactivates* the disk and changes properties on it - REST-API must first deactivate the disk and then change the properties (changing properties while disk is still active will fail). This bug-prone logic is only necessary because when activate/deactivate is merged with update. 
>
>
>
>Option 2 - action 
>=================
>
>.../api/vms/{vm:id}/disks/{disk:id}/attach

Minor correction, I meant .../api/vms/{vm:id}/disks/{disk:id}/activate 
(not .../attach)

>
>Pros:
>----
>* Less RESTful
>
>Cons:
>-----
>* Consistent with other flows
>* Does not have the drawback of the additional business-logic described above
>
>
>Opinions? 
>
>Thanks, 
>
>Ori.