[libvirt-users] libvirtError: block copy still active: disk not ready for pivot yet

[Ala Hino]

I understand that libvirt provides async events that are triggered once the
block job reaches ready state and successfully pivots as it is reported by
qemu.
Whats the event that is triggered and what's the handler that we have to
implement?
To be more specific, I am looking for the onEVENT callback method that is
invoked when the event is fired.

On Tue, Jan 3, 2017 at 6:28 PM, Kashyap Chamarthy <kchamart at redhat.com>
wrote:

> On Wed, Dec 28, 2016 at 01:26:12PM +0200, Ala Hino wrote:
> > Hi guys,
> >
> > When performing live merge, in few cases, we see the following exception:
>
> [...]
>
> > libvirtError: block copy still active: disk 'vdb' not ready for pivot yet
>
> You can see if the block operation is still in progress or not by doing:
> `sudo virsh blockjob vm1 vdb --info`.
>
> > That exception observed in following BZs:
> >
> > https://bugzilla.redhat.com/1376580
> > https://bugzilla.redhat.com/1397122
>
> [I see, that the above are oVirt bugs.]
>
> > I am trying to understand what this exception indicates in order to
> handle
> > it appropriately when thrown by libvirt.
>
> Here's the commit that adds the above error message.  In short: Until
> the 'query-block-jobs' QMP command emits the flag BLOCK_JOB_READY, the
> copy / mirror block operation is truly not complete.
>
>
>     commit eae59247c59aa02147b2b4a50177e8e877fdb218
>     Author: Peter Krempa <pkrempa at redhat.com>
>     Date:   Wed Jul 15 15:11:02 2015 +0200
>
>         qemu: Update state of block job to READY only if it actually is
> ready
>
>         Few parts of the code looked at the current progress of and
> assumed that
>         a two phase blockjob is in the _READY state as soon as the progress
>         reached 100% (info.cur == info.end). In current versions of qemu
> this
>         assumption is invalid and qemu exposes a new flag 'ready' in the
>         query-block-jobs output that is set to true if the job is actually
>         finished.
>
>         This patch adds internal data handling for reading the 'ready'
> flag and
>         acting appropriately as long as the flag is present.
>
>         While this still doesn't fix the virsh client problem with two
> phase
>         block jobs and the --pivot option, it at least improves the error
>         message:
>
>         $ virsh blockcommit  --wait --verbose vm vda  --base vda[1]
> --active --pivot
>         Block commit: [100 %]error: failed to pivot job for disk vda
>         error: internal error: unable to execute QEMU command
> 'block-job-complete': The active block job for device 'drive-virtio-disk0'
> cannot be completed
>
>         to
>
>         $ virsh blockcommit  --wait --verbose VM vda  --base vda[1]
> --active --pivot
>         Block commit: [100 %]error: failed to pivot job for disk vda
>         error: block copy still active: disk 'vda' not ready for pivot yet
>
>
> [...]
>
> --
> /kashyap
>
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