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The nova.virt.xenapi.vm_utils Module

Helper methods for operations related to the management of VM records and their attributes like VDIs, VIFs, as well as their lookup functions.

class nova.virt.xenapi.vm_utils.ImageType
Enumeration class for distinguishing different image types

0 - kernel/ramdisk image (goes on dom0’s filesystem) 1 - disk image (local SR, partitioned by objectstore plugin) 2 - raw disk image (local SR, NOT partitioned by plugin) 3 - vhd disk image (local SR, NOT inspected by XS, PV assumed for

linux, HVM assumed for Windows)
class nova.virt.xenapi.vm_utils.VMHelper

Bases: nova.virt.xenapi.HelperBase

The class that wraps the helper methods together.

classmethod compile_diagnostics(session, record)

Compile VM diagnostics data

classmethod compile_info(record)

Fill record with VM status information

classmethod create_snapshot(session, instance_id, vm_ref, label)

Creates Snapshot (Template) VM, Snapshot VBD, Snapshot VDI, Snapshot VHD

classmethod create_vbd(session, vm_ref, vdi_ref, userdevice, bootable)

Create a VBD record. Returns a Deferred that gives the new VBD reference.

classmethod create_vdi(session, sr_ref, name_label, virtual_size, read_only)

Create a VDI record and returns its reference.

classmethod create_vif(session, vm_ref, network_ref, mac_address, dev, rxtx_cap=0)

Create a VIF record. Returns a Deferred that gives the new VIF reference.

classmethod create_vm(session, instance, kernel, ramdisk, use_pv_kernel=False)

Create a VM record. Returns a Deferred that gives the new VM reference. the use_pv_kernel flag indicates whether the guest is HVM or PV

There are 3 scenarios:

  1. Using paravirtualization, kernel passed in
  2. Using paravirtualization, kernel within the image
  3. Using hardware virtualization
classmethod destroy_vbd(session, vbd_ref)

Destroy VBD from host database

classmethod determine_disk_image_type(instance)

Disk Image Types are used to determine where the kernel will reside within an image. To figure out which type we’re dealing with, we use the following rules:

  1. If we’re using Glance, we can use the image_type field to determine the image_type
  2. If we’re not using Glance, then we need to deduce this based on whether a kernel_id is specified.
classmethod determine_is_pv(session, instance_id, vdi_ref, disk_image_type, os_type)

Determine whether the VM will use a paravirtualized kernel or if it will use hardware virtualization.

  1. Objectstore (any image type): We use plugin to figure out whether the VDI uses PV
  2. Glance (VHD): then we use os_type, raise if not set
  3. Glance (DISK_RAW): use Pygrub to figure out if pv kernel is available
  4. Glance (DISK): pv is assumed
classmethod ensure_free_mem(session, instance)
classmethod fetch_image(session, instance_id, image, user, project, image_type)

image_type is interpreted as an ImageType instance Related flags:

xenapi_image_service = [‘glance’, ‘objectstore’] glance_address = ‘address for glance services’ glance_port = ‘port for glance services’
classmethod find_vbd_by_number(session, vm_ref, number)

Get the VBD reference from the device number

classmethod get_sr(session, sr_label='slices')

Finds the SR named by the given name label and returns the UUID

classmethod get_sr_path(session)

Return the path to our storage repository

This is used when we’re dealing with VHDs directly, either by taking snapshots or by restoring an image in the DISK_VHD format.

classmethod get_vdi_for_vm_safely(session, vm_ref)
classmethod lookup(session, name_label)

Look the instance i up, and returns it if available

classmethod lookup_kernel_ramdisk(session, vm)
classmethod lookup_vm_vdis(session, vm_ref)

Look for the VDIs that are attached to the VM

classmethod preconfigure_instance(session, instance, vdi_ref, network_info)

Makes alterations to the image before launching as part of spawn.

classmethod scan_default_sr(session)

Looks for the system default SR and triggers a re-scan

classmethod scan_sr(session, instance_id=None, sr_ref=None)

Scans the SR specified by sr_ref

classmethod unplug_vbd(session, vbd_ref)

Unplug VBD from VM

classmethod upload_image(session, instance, vdi_uuids, image_id)

Requests that the Glance plugin bundle the specified VDIs and push them into Glance using the specified human-friendly name.

nova.virt.xenapi.vm_utils.find_sr(session)

Return the storage repository to hold VM images

nova.virt.xenapi.vm_utils.get_name_label_for_image(image)
nova.virt.xenapi.vm_utils.get_rrd(host, uuid)

Return the VM RRD XML as a string

nova.virt.xenapi.vm_utils.get_this_vm_ref(session)
nova.virt.xenapi.vm_utils.get_this_vm_uuid()
nova.virt.xenapi.vm_utils.get_vdi_for_vm_safely(session, vm_ref)
nova.virt.xenapi.vm_utils.get_vhd_parent(session, vdi_rec)

Returns the VHD parent of the given VDI record, as a (ref, rec) pair. Returns None if we’re at the root of the tree.

nova.virt.xenapi.vm_utils.get_vhd_parent_uuid(session, vdi_ref)
nova.virt.xenapi.vm_utils.ignore_failure(func, *args, **kwargs)
nova.virt.xenapi.vm_utils.remap_vbd_dev(dev)

Return the appropriate location for a plugged-in VBD device

Ubuntu Maverick moved xvd? -> sd?. This is considered a bug and will be fixed in future versions:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/684875

For now, we work around it by just doing a string replace.

nova.virt.xenapi.vm_utils.safe_find_sr(session)

Same as find_sr except raises a NotFound exception if SR cannot be determined

nova.virt.xenapi.vm_utils.vbd_unplug_with_retry(session, vbd_ref)

Call VBD.unplug on the given VBD, with a retry if we get DEVICE_DETACH_REJECTED. For reasons which I don’t understand, we’re seeing the device still in use, even when all processes using the device should be dead.

nova.virt.xenapi.vm_utils.wait_for_vhd_coalesce(session, instance_id, sr_ref, vdi_ref, original_parent_uuid)

Spin until the parent VHD is coalesced into its parent VHD

Before coalesce:
  • original_parent_vhd
    • parent_vhd

      snapshot

Atter coalesce:
  • parent_vhd

    snapshot

nova.virt.xenapi.vm_utils.with_vdi_attached_here(session, vdi_ref, read_only, f)