libvirt users - Jan 2020 - Re: How to detect completion of a paused VM migration on the destination?

Hi,

when a normally running VM is migrated, libvirt sends
VIR_DOMAIN_EVENT_RESUMED_MIGRATED event on the destination once the
migration completes.  I can see that when a paused VM is migrated,
libvirt sends VIR_DOMAIN_EVENT_SUSPENDED_PAUSED instead.

Since there seems to be nothing migration specific about
VIR_DOMAIN_EVENT_SUSPENDED_PAUSED event, my question is: Is it safe to
assume on the destination that this event signals completion of the
incoming migration (unless VIR_DOMAIN_EVENT_RESUMED_MIGRATED is received
before)?

Thanks,
Milan

On 1/21/20 3:28 PM, Milan Zamazal wrote:
> Hi,
> 
> when a normally running VM is migrated, libvirt sends
> VIR_DOMAIN_EVENT_RESUMED_MIGRATED event on the destination once the
> migration completes.  I can see that when a paused VM is migrated,
> libvirt sends VIR_DOMAIN_EVENT_SUSPENDED_PAUSED instead.
> 
> Since there seems to be nothing migration specific about
> VIR_DOMAIN_EVENT_SUSPENDED_PAUSED event, my question is: Is it safe to
> assume on the destination that this event signals completion of the
> incoming migration (unless VIR_DOMAIN_EVENT_RESUMED_MIGRATED is received
> before)?
Yes. This is the code that handles the finish phase of migration:

https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/qemu/qemu_migration.c;h=29d228a8d9345ec8e2853571444614008a95e914;hb=HEAD#l5105

which can be read as the following pseudo code:

if (postCopy)
   sendEvent(VIR_DOMAIN_EVENT_RESUMED_MIGRATED);

if (domain.paused)
   sendEvent(VIR_DOMAIN_EVENT_SUSPENDED_PAUSED);


Michal

Michal Privoznik <mprivozn@redhat.com> writes:
> On 1/21/20 3:28 PM, Milan Zamazal wrote:
>> Hi,
>>
>
>> when a normally running VM is migrated, libvirt sends
>> VIR_DOMAIN_EVENT_RESUMED_MIGRATED event on the destination once the
>> migration completes.  I can see that when a paused VM is migrated,
>> libvirt sends VIR_DOMAIN_EVENT_SUSPENDED_PAUSED instead.
>>
>> Since there seems to be nothing migration specific about
>> VIR_DOMAIN_EVENT_SUSPENDED_PAUSED event, my question is: Is it safe to
>> assume on the destination that this event signals completion of the
>> incoming migration (unless VIR_DOMAIN_EVENT_RESUMED_MIGRATED is
received
>> before)?
>
> Yes. This is the code that handles the finish phase of migration:
>
>
https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/qemu/qemu_migration.c;h=29d228a8d9345ec8e2853571444614008a95e914;hb=HEAD#l5105
>
> which can be read as the following pseudo code:
>
> if (postCopy)
>   sendEvent(VIR_DOMAIN_EVENT_RESUMED_MIGRATED);
>
> if (domain.paused)
>   sendEvent(VIR_DOMAIN_EVENT_SUSPENDED_PAUSED);
OK, thank you for clarification.

Regards,
Milan