Xen devel - Dec 2005 - domain key gone from xenstore when calling offline hotplug scripts

I''m using a custom vif-script and I''ve noticed that when the
"offline"
mode is called, I''m unable to retrieve the domain key from xenstore, 
most likely because the domain has already been destroyed.

Is there any way to defer the removal of those keys until $vif-script 
offline has been called, or possibly retain it in xend and pass it along 
as a command arg?  The domain value is useful in the network 
deconstruction I''m performing.

Thanks,
-Chris

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On Fri, Dec 09, 2005 at 05:00:24AM -0600, Christopher S. Aker wrote:
> I''m using a custom vif-script and I''ve noticed that when
the "offline"
> mode is called, I''m unable to retrieve the domain key from
xenstore,
> most likely because the domain has already been destroyed.
> 
> Is there any way to defer the removal of those keys until $vif-script 
> offline has been called, or possibly retain it in xend and pass it along 
> as a command arg?  The domain value is useful in the network 
> deconstruction I''m performing.
What do you mean by "the domain key"?  You get the path to the domain,
the
device type and the vif ID passed as environment variables -- this should be
sufficient for you to use as a key to other databases or whathaveyou.  What
else do you require?

Ewan.

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Ewan Mellor wrote:
> On Fri, Dec 09, 2005 at 05:00:24AM -0600, Christopher S. Aker wrote:
> 
>>I''m using a custom vif-script and I''ve noticed that
when the "offline"
>>mode is called, I''m unable to retrieve the domain key from
xenstore,
>>most likely because the domain has already been destroyed.
>>
>>Is there any way to defer the removal of those keys until $vif-script 
>>offline has been called, or possibly retain it in xend and pass it along
>>as a command arg?  The domain value is useful in the network 
>>deconstruction I''m performing.
> 
> 
> What do you mean by "the domain key"?  You get the path to the
domain, the
> device type and the vif ID passed as environment variables -- this should
be
> sufficient for you to use as a key to other databases or whathaveyou.  What
> else do you require?
What''s passed in is the xenstore path to that specific vif''s
backend
entries, for example "backend/vif/26/0".  In
''online'' mode
backend/vif/26/0/domain exists.  In ''offline'' mode, none of
that data is
accessible, or at least the domain entry is no longer there.

I could store the associations between vifs and domainIDs/domain names 
locally and perform lookups, but I was just looking for a xend provided 
method to grab the domain(id) that "owned" the vif we''re
bringing offline.

Thanks,
-Chris

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On Fri, Dec 09, 2005 at 06:19:07AM -0600, Christopher S. Aker wrote:
> Ewan Mellor wrote:
> >On Fri, Dec 09, 2005 at 05:00:24AM -0600, Christopher S. Aker wrote:
> >
> >>I''m using a custom vif-script and I''ve noticed
that when the "offline"
> >>mode is called, I''m unable to retrieve the domain key from
xenstore,
> >>most likely because the domain has already been destroyed.
> >>
> >>Is there any way to defer the removal of those keys until
$vif-script
> >>offline has been called, or possibly retain it in xend and pass it
along
> >>as a command arg?  The domain value is useful in the network 
> >>deconstruction I''m performing.
> >
> >
> >What do you mean by "the domain key"?  You get the path to
the domain, the
> >device type and the vif ID passed as environment variables -- this
should
> >be
> >sufficient for you to use as a key to other databases or whathaveyou. 
What
> >else do you require?
> 
> What''s passed in is the xenstore path to that specific
vif''s backend
> entries, for example "backend/vif/26/0".  In
''online'' mode
> backend/vif/26/0/domain exists.  In ''offline'' mode, none
of that data is
> accessible, or at least the domain entry is no longer there.
> 
> I could store the associations between vifs and domainIDs/domain names 
> locally and perform lookups, but I was just looking for a xend provided 
> method to grab the domain(id) that "owned" the vif we''re
bringing offline.
What are you doing to destroy this domain?  I''ve just tried it with
both xm
destroy and xm shutdown, and I am seeing the backend/vif/26/0/frontend-id node
in both cases.  I would consider it a bug if you are seeing those nodes
disappear before the offline event is fired, so I would be interested in your
help with debugging that, if indeed that''s what you are seeing.

Of course, it would be possible for us to add extra environment variables to
the scripts to contain the information that you require, but I am wary of
doing that, as it clutters the interface and leaves us with more things to
support in the future.

Cheers,

Ewan.

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