On Fri, 6 Jan 2012 17:05:53 +0000 "Daniel P. Berrange" <berra...@redhat.com> wrote:
> On Fri, Jan 06, 2012 at 11:00:42AM -0600, Michael Roth wrote: > > On 01/06/2012 04:56 AM, Daniel P. Berrange wrote: > > >On Thu, Jan 05, 2012 at 06:18:26PM -0600, Michael Roth wrote: > > >>On 01/05/2012 04:26 PM, MATSUDA, Daiki wrote: > > >>>Hi, all. > > >>> > > >>>I am trying QEMU Guest Agent and encountered a small bug. It is that the > > >>>PIDFILE remains when daemon start fails. And maybe forgotton to g_free(). > > >>> > > >>>MATSUDA, Daiki > > >>> > > >> > > >>Thanks for the patch. There was some contention in the past about > > >>whether or not to clean up pidfiles when there was abnormal > > >>termination, but personally I like this approach better. Ok, but can't we use atexit() instead then? > > > > > >Yep, this still leaves open the problem of pidfile cleanup when the > > >daemon crashes. For libvirtd we recently switched over to a crash-safe > > >pidfile acquisition design, that uses fcntl(F_SETLK) to maintain > > >exclusive access over the pidfile. With this you don't need to worry > > >about forgetting to unlink() on termination, since the POSIX lock is > > >automatically released when process exits (or crashes). > > > > Yup, we did the same at some point via lockf(). An argument was made > > that stale PID files from unresolved crashes should stick around, so > > we dropped it. I think we should re-evaluate that decision...libvirt > > taking the same approach is pretty good precedence for me. I don't > > expect to have state from crashed programs interrupting attempts to > > restart them, it's more an unpleasant surprise than a feature, I > > think. Ok, I'll agree with you this time. Let's do it. > > Yeah, I think that is rather unpleasant, particularly for something > like qemu guest agent, which we want to try to ensure is reliably > running. In any case, if qemu guest agent is being launched by > something like SystemD, then you can configure whether systemd > will auto-restart it when it dies with non-zero exit status, so > I don't think we should delibrately leave stale pidfiles for that > scenario. > > Regards, > Daniel
