get_instance_disk_info uses wrong XML to get disk information

Bug #929427 reported by Alvaro Lopez on 2012-02-09
This bug affects 1 person
Affects Status Importance Assigned to Milestone
OpenStack Compute (nova)
Alvaro Lopez

Bug Description

Hi there.

In nova/virt/libvirt/, the get_instance_disk_info method from LibvirtConnection parses the XML returned by virt_dom.XMLDesc. In this XML document, the devices are as follow:

        <disk type='file' device='disk'>
          <driver name='file'/>
          <source file='/srv/nova/instances/instance-00000019/disk'/>
          <target dev='sda' bus='scsi'/>

but the code expects that driver_name has a "type" attribute, containing the type of the driver used (i.e. qcow2, raw). Therefore, if somebody is using raw images instead of cow nova-compute throws an exception, because get_instance_disk_info assumes that the image is qcow and tries to get the backing file (that indeed does not exist for raw images):

    2012-02-09 11:06:51,407 CRITICAL nova [-] list index out of range
    (nova): TRACE: Traceback (most recent call last):
    (nova): TRACE: File "/usr/bin/nova-compute", line 49, in <module>
    (nova): TRACE: service.wait()
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/nova/", line 414, in wait
    (nova): TRACE: _launcher.wait()
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/nova/", line 134, in wait
    (nova): TRACE: service.wait()
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/eventlet/", line 166, in wait
    (nova): TRACE: return self._exit_event.wait()
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/eventlet/", line 116, in wait
    (nova): TRACE: return hubs.get_hub().switch()
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/eventlet/hubs/", line 177, in switch
    (nova): TRACE: return self.greenlet.switch()
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/eventlet/", line 192, in main
    (nova): TRACE: result = function(*args, **kwargs)
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/nova/", line 104, in run_server
    (nova): TRACE: server.start()
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/nova/", line 176, in start
    (nova): TRACE: self.manager.update_available_resource(ctxt)
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/nova/compute/", line 2187, in update_available_resour
    (nova): TRACE: self.driver.update_available_resource(context,
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/", line 1642, in update_availabl
    (nova): TRACE: 'disk_available_least': self.get_disk_available_least()}
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/", line 2002, in get_disk_availa
    (nova): TRACE: disk_infos = utils.loads(self.get_instance_disk_info(i_name))
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/", line 1976, in get_instance_di
    (nova): TRACE: backing_file = libvirt_utils.get_disk_backing_file(path)
    (nova): TRACE: File "/usr/lib/python2.7/dist-packages/nova/virt/libvirt/", line 106, in get_disk_backing_file
    (nova): TRACE: backing_file = os.path.basename(backing_file[0])
    (nova): TRACE: IndexError: list index out of range

I've tested it using libvirt + Xen and using cow and raw images. I do now know if this is the case for other hypervisors, since I do not know the format of the XML returned by libvirt in such cases, but I assume that this should be the

Alvaro Lopez (aloga) on 2012-02-14
Changed in nova:
assignee: nobody → Alvaro Lopez (aloga)
status: New → In Progress

Submitter: Jenkins
Branch: master

commit d1bc92fdbd3aa42b15beeb5eaf2987365247cfa2
Author: Alvaro Lopez Garcia <email address hidden>
Date: Wed Feb 15 11:47:28 2012 +0100

    Fix bug 929427

    We ensure that we are getting the info from a QCOW2 image, not anything

    Change-Id: I8b6bd504da8d52bb9902c917360f0465f9002551

Changed in nova:
status: In Progress → Fix Committed
Thierry Carrez (ttx) on 2012-02-29
Changed in nova:
milestone: none → essex-4
status: Fix Committed → Fix Released
Thierry Carrez (ttx) on 2012-04-05
Changed in nova:
milestone: essex-4 → 2012.1
Alvaro Lopez (aloga) on 2013-11-21
tags: added: libvirt xen
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