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Re: [libvirt] [PATCH] esx: Add vpx:// scheme to allow direct connection to a vCenter



On Sat, Jul 24, 2010 at 09:39:31PM +0200, Matthias Bolte wrote:
> 2010/7/19 Daniel Veillard <veillard redhat com>:
> > On Mon, Jul 19, 2010 at 01:26:10AM +0200, Matthias Bolte wrote:
> >> @@ -49,9 +51,9 @@ esx://example.com/?no_verify=1     (ESX over HTTPS, but doesn't verify the serve
> >>  type://[username ]hostname[:port]/[?extraparameters]
> >
> >
> >  May I suggest a small extra sentence here, explaining how to compose
> > extraparameters ? User may find from lookuing above that they need to
> > use:
> >
> >   arg=value
> >
> > but there is no indication on how to separate multiple parameter.
> 
> That's true. I'll add a sentence or two about that.

  Cool, thanks !


> >  I feel ignorant here. I would assume that a vpx:// connection being to
> > a vCenter vould allow to migrate, care to explain :-) ?
> 
> It will, but migration is tricky. Some more details first:
> 
> An ESX server has one Datacenter, this Datacenter contains one
> ComputeResource and this ComputeResource has a single HostSystem
> attached. Migration is performed between HostSystems in general. Given
> two ESX connections the driver can easily determine the two involved
> HostSystems.
> 
> A vCenter server can have multiple Datacenters, each Datacenter can
> contain multiple ComputeResources. There also might by a special type
> of ComputeResources, the ClusterComputeResource. A
> ClusterComputeResource may have multiple HostSystems attached. To make
> it more complex there is DRS. If DRS is enabled for a
> ClusterComputeResource then the vCenter server will automatically
> control the VirtualMachine to HostSystem mapping. In that case you can
> migrate between ClusterComputeResources and the vCenter will select
> the destination HostSystem for you.
> 
> But with the current vpx:// URI you specify the vCenter only, you
> don't specify the Datacenter or the ComputeResource or the HostSystem
> yet. Therefore, migration using a vpx:// URI doesn't work yet and I
> simply short-circuited the VMotion check for a vpx:// connection for
> now, effectively disabling migration for vpx:// connections.
> 
> I plan to model the Datacenter/ComputeResource/HostSystem selection
> via the path part of the URI:
> vpx://example-vcenter.com/datacenter1/cluster1/hostsystem1
> 
> This allows to omit the HostSystem part in case cluster1 has DRS enabled.
> 
> Migration is a complex topic, I decided to solve it with a later patch
> and to do the simple things first :)

  Okay, I didn't expect that level of complexity, but that's normal, we
are reaching the limits of teh libvirt level, not talking just to an
hypervisor but to a management system, with the DRS implementing user
policies instead of the app managing the software.
  Maybe we could extend virDomainMigrateToURI() to allow a NULL URI in
such case where migration target can be decided by the hypervisor. But
that would have to be exported in the capabilities first.

> > [...]
> >
> >> @@ -2173,6 +2283,7 @@ esxDomainDumpXML(virDomainPtr domain, int flags)
> >>      }
> >>
> >>      esxVI_String_Free(&propertyNameList);
> >> +    esxVI_ObjectContent_Free(&datacenter);
> >>      esxVI_ObjectContent_Free(&virtualMachine);
> >>      VIR_FREE(datastoreName);
> >>      VIR_FREE(directoryName);
> >
> >  I'm a bit suspicious, I see no virFree(datacenterName) here ... normal ?
> 
> Yes, it's obtained via esxVI_GetStringValue from the datacenter
> object. The datacenter object owns the string and the string will be
> freed when the datacenter object gets freed via
> esxVI_ObjectContent_Free(&datacenter).

  okay

> > Okay, overall a very large part of the patch is the change from
> > priv->host to priv->primary, and there is still some TODOs without
> > an error, I assume they will get fixed soon,
> 
> The "TODOs without an error" are the places where I decided to solve
> the complexer parts in a separate patch later and to do the simple
> things first.

  okay, understood, thanks !

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel veillard com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/


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