[libvirt] xen:/// vs. xen://FQDN/ vs xen+unix:/// discrepancy

[Daniel P. Berrange]

On Thu, Jul 22, 2010 at 12:44:53PM +0200, Philipp Hahn wrote:
> Hello,
> 
> I regularly observe the problem, that depending on the libvirt-URL I get 
> different information:
> 
> root at xen4# virsh -c xen://xen4.domain.name/ list
>  Id Name                 State
> ----------------------------------

This will go to the libvirtd daemon, which will in turn open
a 'xen:///' connection

> root at xen4# virsh -c xen:/// list
>  Id Name                 State
> ----------------------------------
>   0 Domain-0             running
>   1 dos4                 idle

This is uses a combination of talking to the hypervisor, xenstore
and xend.

> root at xen4# virsh -c xen+unix:/// list
>  Id Name                 State
> ----------------------------------

This goes to the libvirtd daemon, using UNIX sockets, which
will in turn open a 'xen:///' connection.

Assuming the libvirtd daemon you've connected to is on the
same host as virsh process, then since they all ultimately
end up using 'xen:///', the data should be identical in
all cases.

To verify that libvirtd is actually openening the same drivers as virsh
you can edit /etc/libvirt/libvirtd.conf and set 

  log_filters="1:libvirt 1:xen"
  log_outputs="1:file:/var/log/libvirt/libvirtd.log"

and restart the libvirtd daemon. Then try the 'xen+unix:///' URI again

After that use

  export LIBVIRT_LOG_FILTERS="1:libvirt 1:xen"
  export LIBVIRT_LOG_OUTPUTS="1:file:/var/log/libvirt/libvirtd.log"

and run 'virsh -c xen:///'. It should be possible to then compare that
both sets of logs show same Xen drivers

Daniel
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