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[Roman Podoliaka <rpodolyaka@xxxxxxxxxxxx>]

** Also affects: mos/5.1.x
   Importance: High
     Assignee: MOS Nova (mos-nova)
       Status: In Progress

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https://bugs.launchpad.net/bugs/1332660

Title:
  Update statistics from computes if RBD ephemeral is used

Status in Fuel: OpenStack installer that works:
  In Progress
Status in Fuel for OpenStack 4.1.x series:
  In Progress
Status in Fuel for OpenStack 5.0.x series:
  In Progress
Status in Mirantis OpenStack:
  In Progress
Status in Mirantis OpenStack 5.0.x series:
  In Progress
Status in Mirantis OpenStack 5.1.x series:
  In Progress
Status in OpenStack Compute (Nova):
  In Progress

Bug description:
  If we use RBD as the backend for ephemeral drives, compute nodes still calculate their available disk size looking back to the local disks.
  This is the path how they do it:

  * nova/compute/manager.py

      def update_available_resource(self, context):
          """See driver.get_available_resource()

          Periodic process that keeps that the compute host's understanding of
          resource availability and usage in sync with the underlying hypervisor.

          :param context: security context
          """
          new_resource_tracker_dict = {}
          nodenames = set(self.driver.get_available_nodes())
          for nodename in nodenames:
              rt = self._get_resource_tracker(nodename)
              rt.update_available_resource(context)
              new_resource_tracker_dict[nodename] = rt
  ....................
      def _get_resource_tracker(self, nodename):
          rt = self._resource_tracker_dict.get(nodename)
          if not rt:
              if not self.driver.node_is_available(nodename):
                  raise exception.NovaException(
                          _("%s is not a valid node managed by this "
                            "compute host.") % nodename)

              rt = resource_tracker.ResourceTracker(self.host,
                                                    self.driver,
                                                    nodename)
              self._resource_tracker_dict[nodename] = rt
          return rt

  * nova/compute/resource_tracker.py

      def update_available_resource(self, context):
          """Override in-memory calculations of compute node resource usage based
          on data audited from the hypervisor layer.

          Add in resource claims in progress to account for operations that have
          declared a need for resources, but not necessarily retrieved them from
          the hypervisor layer yet.
          """
          LOG.audit(_("Auditing locally available compute resources"))
          resources = self.driver.get_available_resource(self.nodename)

  * nova/virt/libvirt/driver.py

      def get_local_gb_info():
          """Get local storage info of the compute node in GB.

          :returns: A dict containing:
               :total: How big the overall usable filesystem is (in gigabytes)
               :free: How much space is free (in gigabytes)
               :used: How much space is used (in gigabytes)
          """

          if CONF.libvirt_images_type == 'lvm':
              info = libvirt_utils.get_volume_group_info(
                                   CONF.libvirt_images_volume_group)
          else:
              info = libvirt_utils.get_fs_info(CONF.instances_path)

          for (k, v) in info.iteritems():
              info[k] = v / (1024 ** 3)

          return info

  
  It would be nice to have something like "libvirt_utils.get_rbd_info" which could be used in case CONF.libvirt_images_type == 'rbd'

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