Re: [Xen-API] Xen-API Preview Tree

[Ewan Mellor <ewan@xxxxxxxxxxxxx>]

On Mon, Oct 09, 2006 at 06:47:37PM +0100, Daniel P. Berrange wrote:

> With the lifecycle patches, 'xm list' and 'GET /xend/domains' will now
> include inactive domains as well as active domains. eg
> 
>   # xm list
>   Name                              ID Mem(MiB) VCPUs State  Time(s)
>   Domain-0                           0      594     2 r-----    22.2
>   guest3                            -1      400     1 ------    14.7
> 
> This can cause a slight compatability problem because there has previously
> been the tacit assumption that "ID" is a unique way to refer to a domain
> running on a box. With all inactive domains now returning '-1' this is no
> longer valid. So I think that returning inactive domains by default for
> commands line 'xm list' or the raw  'GET /xend/domains' may well cause
> compatability problems for existing users of this command / API. 

Note that the domain ID is a unique identifier for the domain, but _not_ a
unique identifier for a VM.  If a VM is migrating to localhost, for example,
then a given VM may have two different domain IDs.

That said, I certainly agree that the change in semantics of the old protocol
is inappropriate, and I'll put that on the list to be fixed.  Your
proposal for a flag to xm list sounds fine to me also (though I'm
tempted to word it as "state=Running" rather than "scope=active", to
reuse the existing VM state mechanisms).  Regardless of the details, the
basic idea is sound, and we'll put that in certainly.

> In the actual listing of domains in XM, I think its probably more desirable
> to just have a '-' in the ID column for inactive domains, rather than -1,s
> since this indicates more clearly that there is no effective ID for inactive
> domains, eg 
> 
>   # xm list
>   Name                              ID Mem(MiB) VCPUs State  Time(s)
>   Domain-0                           0      594     2 r-----    22.2
>   guest3                             -      400     1 ------    14.7

Sure, sounds fine.

> Finally, I'd also like to see the 'xend_config_version' field for 'xm info'
> incremented from '2' to '3' to allow clients to easily detect that the XenD
> they're talking to has this new capability for configs.

Definitely.

Thanks for that,

Ewan.

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