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On Wed, 2016-08-24 at 11:18 -0400, Daniel P. Berrange wrote:
> On Wed, Aug 24, 2016 at 05:07:50PM +0200, Alberto Planas Dominguez
> wrote:

Daniel, thanks for the fast reply!!

> > Unfortunately was closed as invalid, and the solution provided is
> > completely unrelated. The solution suggested is based on
> > `live_migration_inbound_addr`, that is related with the libvirtd
> > URI,
> > not the qmeu one. I tested several times and yes, this solution is
> > not
> > related with the problem.
> 
> The "live_migration_inbound_addr" configuration parameters was
> intended
> to affect both libvirt & QEMU traffic. If that is not working
> correctly,
> then we should be fixing that, nto adding yet another parameter.

The code in libvirt is very clear: if uri_in is NULL will ask to the
hostname to the other side. I checked the code in 1.2.18:

https://github.com/libvirt/libvirt/blob/v1.2.18-maint/src/qemu/qemu_mig
ration.c#L3601

https://github.com/libvirt/libvirt/blob/v1.2.18-maint/src/qemu/qemu_mig
ration.c#L3615

The same logic is in master:

https://github.com/libvirt/libvirt/blob/master/src/qemu/qemu_migration.
c#L4013

But we can go back to 0.9.12:

https://github.com/libvirt/libvirt/blob/v0.9.12-maint/src/qemu/qemu_mig
ration.c#L1472

Nova set migration_uri parameter to None, that this means that uri_in
is NULL.

How can I affect the the QEMU part? The code path AAIU is: if we do not
set miguri (migrateToURI2) or migrate_uri (migrateToURI3), is a
uri_in=NULL.

I am not familiar with libvirt code, please, help me to find how I can
affect this uri_in parameter to have a value different from the
hostname of the other node, without setting the correct value in
migrateToURI[23] in the Nova side.


> > this patch will create a second uri:
> > 
> > migrate_uri=tcp://fast.%s/
> 
> While you can do that hack, the fact that is works is simply luck -
> it
> certainly was not designed with this kind of usage in mind. We would
> in fact like to remove the live_migration_uri config parameter
> entirely
> and having the libvirt driver automatically use the correct URI.

This is a very interesting suggestion!

I can see that in /etc/libvirt.qemu.conf there is a parameter for
'migration_address', that is the -incoming side of the migration. What
I am not able to see is how I can change the hostname (to select the
correct interface) from the source of the migration. I see the default
value in `migration_host`, but my tests didn't work to set the uri_in
properly

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