Re: Proposal: deprecate "vncviewer" option in xl domain config file

[Wei Liu <wei.liu2@citrix.com>]

On Tue, Apr 22, 2014 at 04:50:56PM +0100, Ian Campbell wrote:
> On Tue, 2014-04-22 at 16:19 +0100, Wei Liu wrote:
> > Hi all
> > 
> > When I'm working on (de-)serialization of domain configurations I found
> > "vncviewer". I now propose to deprecate it.
> > 
> > What it does is that if you have it set in your domain's config file and
> > do "xl create cfg", xl will automatically spawn a vncviewer for you.
> > This option actually controls the creation process of a domain but has
> > nothing to do with domain configuration at all.
> > 
> > This option is buggy because it's also saved as part of domain state
> > when you do save / restore.
> 
> Where is it saved?
> 

The domain config file is saved, then used when restoring. Restoring
process involves re-parsing that config file.

> >  Consider user migrates a domain to a remote
> > host, xl will try to auto-spawn vncviewer on the new host. This behavior
> > doesn't make sense at all.
> > 
> > Further more it becomes an obstacle for the work to (de-)serialization
> > domain configurations. If we want to preserve this option we then need
> > to create abstraction for a config file in xl or libxl. This either
> > introduces lots of work without much benefit (if we add out-of-band
> > infomation in xl) or pollute libxl public interface.
> > 
> > I propose to deprecate this option.
> > 
> > What I will do is:
> > 1. config file still supports this option but it will prints out a
> >    warning about its deprecation.
> > 2. this option is not saved as domain state when doing save / restore,
> >    so when you restore a domain xl will not auto-spawn vncviewer.
> > 
> > This may create a minor regression, but it's in no way critical. In
> > any case the right way to auto-spawn vncviewer is to use "-V" in "xl
> > create". And existing user of this config file option can also use "-V"
> > to work around this regression.
> > 
> > Comments?
> 
> Rather than throwing the baby out with the bathwater can't we just say
> that this option is only obeyed for the initial domain creation and not
> for any subsequent migration or restore? What would avoid the need to
> propagate it along with the save/migrate image.
> 

I think this is just wording issue. My "xl-json" format patch does this
already.  I'm OK with any approach as long as I don't need to propogate
it. :-P

Wei.

> Ian.
>