[Libvir] Request for additional entry points

Daniel Veillard veillard at redhat.com
Wed Apr 12 08:25:49 UTC 2006

On Wed, Apr 12, 2006 at 04:08:53AM +0100, Daniel P. Berrange wrote:
> I'd actually question whether libvirt should have any concept of 'passive'
> or 'inactive' domains at all. Just to play out a few scenarios:

  The 2 first scenarios assume the passive domains are stored on the 
disk. This doesn't has to be the case, libvirt could just cache those
informations in the management tool memory, also xenstore is acessed via
RPC, those might be extended for remote machines.

>  * Definitions of inactive domains are stored on a remote server, libvirt
>    has no visibilty into this system. virDomainSetConfig() would not help
>    since there is no concept of a domain being inactive on a single host,
>    rather inactive domains can be deployed to any host in the server farm
>    at will.
>  * Definitions are visible on the local filesystem, but this FS is shared
>    NFS / SAN storage. Again while their config files may be technically
>    visible via the shared filesystem, there is no meaningful association
>    between an inactive config & a host.
>  * Domains are created from config 'templates'. The template defines a
>    generic resource configuration, turned into a fully fledged config
>    on-demand - perhaps with the variables plugged into the template
>    coming from an alternate datastore (SQL databsae perhaps). In this
>    case there would be no sense in storing pre-made XML configs, since
>    the master info is a combo of the template & SQL database entries.

  In general I agree that reliance on some filesystem storage for them
is a serious problem.

> So, really the only case where there is any meaningful concept of 'passive'
> domain configs associated with a static single host model - for example that
> provided by XenD which happen to have a simple store of inactive domains
> in /etc/xen.

  No that could work too if libvirt used to manage remote domains from a
centralized location and keep the passive domain definitions on that 
centralized server.

> Thinking about what tools might need information on inactive domains:
>  - Desktop management tool - cf VMWare Workstation. Possibly, but even
>    here there is no reason such a tool represents inactive domains in
>    terms of a libvirt XML config file. It may well have generic templates
>    eg 'Linux Web Server  and instances 'web0.google.com', 'web1.google.com',
>    'web2.google.com', where the only instance specific data is the hostname
>    and master disk image.
>  - Data center management tool - it may well have a concept of inactive
>    domain configs, but it almost certainly won't be associated with a
>    single host, so unlikely to be asking libvirt to list inactive domains. 

  The need comes from the second one, this is part of the CIM model.


Daniel Veillard      | Red Hat http://redhat.com/
veillard at redhat.com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
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