Re: [Xen-devel] [PATCH RFC V2 10/10] xl: introduce "xl-json" format

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Sat, 2014-04-19 at 09:35 +0100, Wei Liu wrote:
> On Thu, Apr 17, 2014 at 12:13:11PM +0100, Wei Liu wrote:
> > Originally xl verbatimly copies the domain config file in its user data
> > store. This patch adds the functionality to transform text domain config
> > file to JSON object and save that object in user data store.
> > 
> > What this patch does:
> > 1. add a mandatory flag to save protocol to indicate whether the saved
> >    config is a JSON object
> > 2. register a new private data type "xl-json" in libxl.h
> > 3. modify xl to save / load "xl-json" file where necessary
> > 
> > After this change xl supports both "xl" format and "xl-json" format.
> > The user-supplied config file is still restricted to normal text config
> > file format ("xl"), as xl has more sanity checks when parsing text
> > config file. "xl-json" format is only used internally. The saved config
> > file is always in "xl-json" format.
> > 
> > Tests done so far (xl.{new,old} denotes xl with{,out} "xl_json"
> > support):
> > 1. xl.new create then hexdump saved file: domain config saved in JSON format
> > 2. xl.new create then xl.old restore: failed on mandatory flag check
> > 3. xl.new create then xl.new restore: succeeded
> > 4. xl.old create then xl.new restore: succeeded
> > 5. xl.new create then local migrate, receiving end xl.new: succeeded
> > 6. xl.old create then local migrate, receiving end xl.new: succeeded
> > 
> > The only drawback is that when restoring a domain, xl cannot
> > automatically spawn a vncviewer anymore. That's because that option is
> > part of domain_create info not a domain configuration thus it's not
> > saved in the JSON config.
> > 
> 
> On a second thought I might as well create abstraction of a config file
> in IDL. This might be more flexible in the long run. Then the burden
> will be whenever an option that doesn't belong to domain_config is
> added, IDL will also need to be taken care of.

Is the issue here that the vnc autospawning is controlled via the xl
command line (-A) rather than something in the configuration file? Or is
there a config file way to do this too?

If it's because it is on the command line then we should be propagating
that to the xl migrate-restore perhaps.

We could also have xl transmit some state of its own outside of the
domain configuration, either by using the IDL to do it in JSON or some
other mechanism.

I'm not sure about adding things to the libxl interface which libxl
itself doesn't deal with just as a way to conveniently carry the
information around.

Ian.


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