Re: [Xen-devel] [PATCH] xenctld - a control channel multiplexing daemon

[Tobias Hunger <tobias@xxxxxxxxxxx>]

On Thursday 27 January 2005 00:59, Daniel Stekloff wrote:
> Can't we add functionality in Xen to make domain id's unique? When
> creating a new domain, the management tools can query the running (or
> even suspended) domains and find a unique domain id to use. I think you
> can tag a domains with their state.

Hey, that is exactly what I was thinking when reading that mail:-) Some new 
states like 'unconfigured' etc. might need to get added.

> If you clone a domain, it isn't the same domain anymore and would get a
> new id.

... so the ID needs to be unique on a per machine basis only: If you clone and 
then migrate a domain to another machine the copy will get a new ID there.

> As for checkpointing - you could use the time/date of the 
> checkpoint and add that to the domain's id.

Or a a simple counter that gets incremented, that is easier to work with. 
Creation date (and maybe creator) could get stored as some attribute along 
with the configuration, independent of whether the set of attributes is a 
checkpoint or a "normal" domain.

> MAC addresses for specific domains that are in the configuration file or
> generated could be stored with the domain configuration and available
> for queries.

Yeap. Management tools can then query the state and migrate those settings as 
necessary. This approach reduces the amount of policy coded into the core of 
xen. I like it.

> I disagree. If we're to consider the larger management world, we need to
> lay the groundwork for managing domains now. I think the questions
> aren't easily answered, but I believe they should be. If we don't
> implement everything to start, we should at least have an idea where
> we're going.

I have to agree with Dan again:-) Xen can proof that its concepts hold and can 
be implemented. But all the flexibility xen adds is only worth as much as the 
tools provided to manage it.

In my opinion unique DomIds are a good idea anyway: They make configuration 
easier since you can just hardcode DomIds into the config files. Currently 
you have to use domain names in some places and those have to be parsed at 
setup time to figure out which domains are actually referred to. I even have 
to edit some of my config files all the time since the name-hack is not 
supported in all cases (namely backend in the vif-setup). As an additional 
complication there is no requirement on the DomNames to be unique.

PS: This proposed filesystem-based config storage sounds like you could 
leverage the elektra project for data storage. That is a simple lib for 
registry-like storage of key/value pairs. It features few dependencies and 
python bindings:-) The URL is http://elektra.sf.net/.

-- 
Gruss,
Tobias

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Tobias Hunger           The box said: 'Windows 95 or better'
tobias@xxxxxxxxxxx                     So I installed Linux.
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