[libvirt] Python listDefinedDomains broken?

[Pavel Hrdina]

On Wed, Jun 01, 2016 at 02:03:17PM +0100, Daniel P. Berrange wrote:
> On Wed, Jun 01, 2016 at 02:49:26PM +0200, Marc Richter wrote:
> > Hi everyone,
> > 
> > please, don't roast me if I'm asking stupid things or fail to provide info,
> > since I'm a freshman, using libvirt.
> 
> No problem, we're a friendly lot here :-)
> 
> > Then a domain named "winxp_ausgeschaltet" is within that list:
> > 
> > 
> >  Id    Name                           State
> > ----------------------------------------------------
> > ...
> >  -     winxp_ausgeschaltet            shut off
> > 
> > 
> > When I do the same for the second host, it is also in that list:
> > 
> > 
> >  Id    Name                           State
> > ----------------------------------------------------
> > ...
> >  7     winxp_ausgeschaltet            running
> > 
> > 
> > When I do the following in Python, this domain is listed for the first host
> > (where it's state is "shut off"), but not for the second one:
> > 
> > 
> > import libvirt
> > import sys
> > 
> > class kvmhost:
> >     def __init__(self, host, keyfile):
> >         self.conn = self.connect_kvm(host, keyfile)
> >         self.doms = sorted(self.get_doms())
> >     def connect_kvm(self, host, keyfile):
> >         try:
> >             conn = libvirt.openReadOnly('qemu+ssh://root@' + host +
> > '/system?keyfile=' + keyfile)
> >         except libvirt.libvirtError as lve:
> >             print('Error: ' + str(lve))
> >             sys.exit(1)
> >         return conn
> >     def get_doms(self):
> >         try:
> >             alldoms = self.conn.listDefinedDomains()
> >         except libvirt.libvirtError as lve:
> >             print('Error: ' + str(lve))
> >             self.conn.close()
> >             sys.exit(1)
> >         return alldoms
> > 
> > host1 = kvmhost('host1', '/path/to/ssh_keyfile')
> > host2 = kvmhost('host2', '/path/to/ssh_keyfile')
> > 
> > print(host1.doms)
> > print(host2.doms)
> > 
> > 
> > What am I doing wrong here or: is there a missbehavior in libvirt or the
> > python module?
> 
> This is expected behaviour of the listDefinedDomains() API call - though
> admittedly somewhat stupid behaviour.
> 
> Originally libvirt has a listDomainsIDs API call that only listed guests
> that were running.
> 
> We then added  listDefinedDomains() call that only listed guests that
> were *not* running.
> 
> So to get a complete list of guests on the host you had to use *both*
> listDomainsIDs and listDefinedDomains().
> 
> This had a built-in race condition if a guest started or stopped in
> betweeen the 2 API calls. So we introduced 'listAllDomains' as a better
> API that can give you a list of *all* domains whether running or stopped.
> 
> > Using listAllDomains instead of listDefinedDomains gives:
> > 
> > libvirt: Remote Driver error : unknown procedure: 273
> 
> I'm really surprised to see that error - this API call has existed
> since libvirt 0.9.13 and you say you have 1.3.1 which is more than
> new enough

I thing that the version of libvirt on the workstation is 1.3.1 but both servers
seems to have pretty old system.  The qemu version is 0.14.0.  If we consider
for example Fedora, qemu-0.14.0 was released in Fedora 15 where libvirt version
is 0.8.8.  That would explain the error message, that both servers has ancient
version of OSes.

Pavel

> 
> > What is the difference between listAllDomains and listDefinedDomains at all?
> 
> Essentially listAllDomains() is what any app using modern libvirt should
> be using. We recommend ignoring listDefinedDomains & listDomainIDs unless
> you need to work with older (ancient) libvirt
> 
> Regards,
> Daniel
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