[libvirt] [PATCHv2 02/26] snapshot: better event when reverting qemu to paused snapshot
Daniel P. Berrange
berrange at redhat.com
Wed Aug 24 15:06:43 UTC 2011
On Wed, Aug 24, 2011 at 08:23:55AM -0600, Eric Blake wrote:
> On 08/24/2011 08:21 AM, Daniel P. Berrange wrote:
> >>+++ b/src/qemu/qemu_driver.c
> >>@@ -8804,14 +8804,16 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
> >> QEMU_ASYNC_JOB_NONE);
> >> if (rc< 0)
> >> goto endjob;
> >>+ event = virDomainEventNewFromObj(vm,
> >>+ VIR_DOMAIN_EVENT_SUSPENDED,
> >>+ VIR_DOMAIN_EVENT_SUSPENDED_FROM_SNAPSHOT);
> >> } else {
> >> virDomainObjSetState(vm, VIR_DOMAIN_RUNNING,
> >> VIR_DOMAIN_RUNNING_FROM_SNAPSHOT);
> >>+ event = virDomainEventNewFromObj(vm,
> >>+ VIR_DOMAIN_EVENT_STARTED,
> >>+ VIR_DOMAIN_EVENT_STARTED_FROM_SNAPSHOT);
> >> }
> >>-
> >>- event = virDomainEventNewFromObj(vm,
> >>- VIR_DOMAIN_EVENT_STARTED,
> >>- VIR_DOMAIN_EVENT_STARTED_FROM_SNAPSHOT);
> >> } else {
> >
> >This isn't so nice. The lifecycle model for VMs is
> >
> > shutoff<----> running<------>paused
>
> Even when you use virDomainCreateWithFlags(, VIR_DOMAIN_START_PAUSED)?
When you do that, it should be viewed as 2 transitions. From shutoff
to running, to paused.
Currently we will emit a 'STARTED' event there, but are missing a
SUSPENDED event there.
> >This change creates a direct transition from shutoff to paused, missing
> >out the running state, which will break any apps which are just looking
> >to find out when guests stop/start and don't care about pause/resume.
> >Also
> >
> > virsh start --paused $GUEST
> >
> >will only emit a 'VIR_DOMAIN_EVENT_STARTED', so the current beahviour for
> >reverting to a paused snapshot matches that.
> >
> >Arguably we could *also* emit an VIR_DOMAIN_EVENT_SUSPENDED, immediately
> >*after* the VIR_DOMAIN_EVENT_STARTED, in both cases though.
>
> This may have bigger cleanup impact, then, if we want to guarantee
> both STARTED and SUSPENDED events on all code paths where we can
> start life paused.
I believe migration deals with it correctly. The restore/boot up paths
likely need fixing
Daniel
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