On 06/09/2010 10:31 AM, Daniel P. Berrange wrote:
However, libvirt was counting on this feature and on the snapshot commands
to switch from the text Monitor. We have two options:
1. Ask them to wait one more release (not so good for us)
2. Try to find a way to have those features in for 0.13
Daniel has commented to me that making the snapshot commands synchronous
for 0.13 wouldn't be that bad, what do you think?
The thought is that changing a command from synchronous to asynchronous is
not an ABI incompatible change. An existing app simply won't know to take
advantage of the new possibilities that async commands offer.
It's not QMP that's the major issue with savevm. The major issue is
actually the way snapshots are saved in qcow2. You need to know the
size of the snapshot prior to creating the snapshot which is not
possible if you want to make snapshots live. In order to support this
functionality, we'll probably have to introduce a new snapshot format in
qcow2.
Honestly, I would recommend not supporting snapshots in libvirt until we
did the work to make snapshots live. Snapshots can cause guests to
generate errors as it stands today and fixing that will almost certainly
result in backwards compatibility considerations.
If we did put savevm in QMP today, we would need to provide an interface
that let applications detect when we eventually fix this.
Regards,
Anthony Liguori
Regards,
Daniel
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