[libvirt] [PATCH v4 1/1] migration: add support for migrateURI configuration

[chen.fan.fnst at cn.fujitsu.com]

On Fri, 2014-05-16 at 09:51 -0400, Daniel P. Berrange wrote: 
> On Thu, May 15, 2014 at 11:50:54AM +0200, Jiri Denemark wrote:
> > On Wed, May 14, 2014 at 15:18:09 +0800, Chen Fan wrote:
> > > For now, we set the migration URI via command line '--migrate_uri' or
> > > construct the URI by looking up the dest host's hostname which could be
> > > solved by DNS automatically.
> > > 
> > > But in cases the dest host have two or more NICs to reach, we may need to
> > > send the migration data over a specific NIC which is different from the
> > > automatically resloved one for some reason like performance, security, etc.
> > > thus we must explicitly specify the migrateuri in command line everytime,
> > > but it is too troublesome if there are many such hosts(and don't forget
> > > virt-manager).
> > > 
> > > This patches add a configuration file option on dest host to save the
> > > default migrate uri which explicitly specify which of this host's
> > > addresses is used for transferring data, thus user doesn't boring
> > > to specify it in command line everytime.
> > > 
> > > Signed-off-by: Chen Fan <chen.fan.fnst at cn.fujitsu.com>
> > > ---
> > > 
> > > v3-v4: move up the default uri_in setting to
> > >        qemuDomainMigratePrepare3Params()
> > > 
> > >  src/qemu/qemu.conf     | 6 +++++-
> > >  src/qemu/qemu_conf.c   | 1 +
> > >  src/qemu/qemu_conf.h   | 1 +
> > >  src/qemu/qemu_driver.c | 2 +-
> > >  4 files changed, 8 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
> > > index f0e802f..6b443d0 100644
> > > --- a/src/qemu/qemu.conf
> > > +++ b/src/qemu/qemu.conf
> > > @@ -449,7 +449,11 @@
> > >  #
> > >  #seccomp_sandbox = 1
> > >  
> > > -
> > > +# Override the migration URI for specifying one of host's IP addresses
> > > +# to transfer the migration data stream.
> > > +# Defaults to hostname, both IPv4 and IPv6 addresses are accepted.
> > > +#
> > > +#migrate_uri = "tcp://192.168.0.1"
> > >  
> > >  # Override the listen address for all incoming migrations. Defaults to
> > >  # 0.0.0.0, or :: if both host and qemu are capable of IPv6.
> > 
> > The more I think about this the more I incline to a slightly different
> > approach. Rather than providing a way to override migration URI, we
> > could just provide an option in libvirtd.conf to override what
> > virGetHostname returns. That is, the option (naturally called hostname)
> > would tell libvirt to use the configured hostname (which might even be
> > just an IP address) instead of trying to detect it.
> 
> I'm not sure this is a good idea. The hostname is used in a number of places
> in libvirt, and we don't neccessarily want them all to use the same interface
> as the migration data. eg if you have a NIC that is dedicated just for migration
> traffic, you won't want to force other parts of libvirt to use that. So having
> the migration hostname specified separately is a good idea IMHO. Perhaps we
> could simplify though by having 'migrate_host' rather than 'migrate_uri' ?
I think that is a good idea. I would like to implement them.

Thanks,
Chen




> 
> And perhaps we do want a hostname override globally anyway, for other reasons.
> 
> 
> Regards,
> Daniel