[Xen-devel] Re: [RFC] Switching store to use domain id's for keys

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Christian Limpach wrote:

> > The reasoning seems obvious to me, there's no easy way to get the UUID 
> > for a domain so constructing a UUID based path outside of Xend is very 
> > difficult.
> >    
> Hmm, it's less than 40 lines of C code to iterate over the /domain entries
> and find a domain with a matching name or id.  It would be convenient
> to have library functions which does this...
>  
The linear search just makes me sad :-)  There can still be a UUID key 
within the /domain tree.  One can just as easily code up a function to 
resolve UUIDs to domain IDs by doing a linear search.
I think the key is to optimize for the common case here.  Since, today 
and I reckon for the foreseeable future, the management functions take 
domain IDs, it seems like the right thing to optimize for.
> We'd like the identifier for a domain to remain the same after
> relocating the domain to a different physical machine.[1]
>  
Yes, this is a tough thing to get right.  It straight forward for 
migration, but what about save/restore, cloning, etc.  It seems almost 
better to let UUIDs preservation to be a higher level management task.
> If we consider changing this, I'd go for /domain/<nodeid>-<domid>.  It
> would make it easy to find the path for a domain on its home node but
> it wouldn't work anymore once you move the domain to a new host.
>  
I'm partial to a more hierarchical model.  Something like 
<nodeid>/domain/<domid>.  It lets <nodeid> become part of an implicit 
path...
Regards,

Anthony Liguori

> > Or, if we really want to use UUIDs in the node path, perhaps we can add 
> > UUIDs to the domain structure in the hypervisor so that we can actually 
> > query it through getdomaininfo?
> >    
> We've considered this but everytime we've found that the reason why
> we wanted it was invalid.
>
> In any case, it seems reasonable to move the console entries to the
> domain tree then...
>
>    christian
>
> [1] this is currently broken since we create a new uuid on restore.
> The issue is that device configuration is local to the host where the
> domain is running and there's a short period of time where we want
> device information for two hosts present at the same time.
>
>
>  

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