On Fri, Mar 09, 2007 at 02:02:55PM +0000, Richard W.M. Jones wrote: > Richard W.M. Jones wrote: > >Daniel P. Berrange wrote: > >>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. > > > >Is it possible to start qemu with something like: > > > > qemu -monitor pipe:/var/some/known/place/pipe.UUID > > > >and then just look in /var/some/known/place/ in order to find the > >running instances? > > I should add a note that you can tell if the qemu at the other end of > the pipe has died by opening the pipe and writing something, for example > a NO-OP command. If you get EPIPE (or SIGPIPE if you weren't careful to > disable the signal) you can delete the pipe device.
Yes, that could be a very useful way to detect guest shutdown without needing to maintain the PPID<->PID relationship & waitpid(). Definitely something to experiment with in the near future. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=| -- Libvir-list mailing list Libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
