[Libvir] Restarting of libvirt_qemud daemon

Daniel P. Berrange berrange at redhat.com
Fri Mar 9 13:47:31 UTC 2007

On Fri, Mar 09, 2007 at 10:47:18AM +0000, Richard W.M. Jones wrote:
> Daniel P. Berrange wrote:
> >Thinking about later RPM upgrades I think we need to think about whether it
> >will be possible to restart the libvirt_qemud while guests & networks are
> >running. There's a couple of issues:
> >
> > - We do waitpid() to cleanup qemu & dnsmasq processes when we stop domains
> >   & networks, or to detect when they crash. For the former, we could may
> >   they daemons to avoid waitpid() cleanup, but we'd still need waitpid to
> >   be able to detect shutdowns. There is also the issue of enumerating
> >   running instances.
> Maybe I'm missing something big here, but how would libvirt_qemud regain 
> connections to the running qemu monitor ptys?

That's one of the challenges to be addressed :-)  Fortunately the monitor
is set to be exposed via /dev/pty/XXX, so if the restarted client can
find out the path to the PTY, then it can re-open it. Maybe we just need
to record a state file somewhere containing a PID & PTY path. 

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