[libvirt] [PATCH] 514532 Fix man page, most operation are synchronous

Daniel Veillard veillard at redhat.com
Thu Nov 19 17:02:26 UTC 2009

On Thu, Nov 19, 2009 at 04:34:12PM +0000, Daniel P. Berrange wrote:
> On Wed, Nov 18, 2009 at 02:31:12PM +0100, Daniel Veillard wrote:
> >  
> > -Most B<virsh> commands act asynchronously, so just because the B<virsh>
> > -program returned, doesn't mean the action is complete.  This is
> > -important, as many operations on domains, like create and shutdown,
> > -can take considerable time (30 seconds or more) to bring the machine
> > -into a fully compliant state.  If you want to know when one of these
> > -actions has finished you must poll through virsh list periodically.
> > +Most B<virsh> commands act synchronously, except maybe shutdown
> > +and domain creation. In those case the fact that the B<virsh>
> > +program returned, may not mean the action is complete and you
> > +must poll through virsh list periodically to detect that the
> > +operation completed.
> Shutdown is async, but domain creation is certainly supposed to
> be synchronous.    Of course the guest may immediately crash
> so appear inactive again just after create returns

Well I was also thinking that Create like Shutdown, the process is at best
started in the Domain OS but completion can't be asserted just because
the command started. I think the idea of creating the guess is also
implicitely tied with the OS booting th the mind of users, and well
their domain won't respond to requests for a little bit even if the
create succeeded.

> Thinking about it, I believe virDomainShutdown/Reboot, and the SetMemory
> and SetVcpus are the only two APIs that are allowed to be async, because 
> they merely update the guest, but don't wait for it to react.

  I was wondering for all our storage operations, some of thse can
certainly take a very long time. Network operations should be more or
less instant.


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

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