text: # Copyright 2016 Dell Inc.
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  """
  Core backend volume driver interface.
  
  All backend drivers should support this interface as a bare minimum.
  """
  
  from cinder.interface import base
  
  
  class VolumeDriverCore(base.CinderInterface):
      """Core backend driver required interface."""
  
      def do_setup(self, context):
          """Any initialization the volume driver needs to do while starting.
  
          Called once by the manager after the driver is loaded.
          Can be used to set up clients, check licenses, set up protocol
          specific helpers, etc.
  
          :param context: The admin context.
          """
  
      def check_for_setup_error(self):
          """Validate there are no issues with the driver configuration.
  
          Called after do_setup(). Driver initialization can occur there or in
          this call, but must be complete by the time this returns.
  
          If this method raises an exception, the driver will be left in an
          "uninitialized" state by the volume manager, which means that it will
          not be sent requests for volume operations.
  
          This method typically checks things like whether the configured
          credentials can be used to log in the storage backend, and whether any
          external dependencies are present and working.
  
          :raises: VolumeBackendAPIException in case of setup error.
          """
  
      def get_volume_stats(self, refresh=False):
          """Collects volume backend stats.
  
          The get_volume_stats method is used by the volume manager to collect
          information from the driver instance related to information about the
          driver, available and used space, and driver/backend capabilities.
  
          It returns a dict with the following required fields:
  
          * volume_backend_name
              This is an identifier for the backend taken from cinder.conf.
              Useful when using multi-backend.
          * vendor_name
              Vendor/author of the driver who serves as the contact for the
              driver's development and support.
          * driver_version
              The driver version is logged at cinder-volume startup and is useful
              for tying volume service logs to a specific release of the code.
              There are currently no rules for how or when this is updated, but
              it tends to follow typical major.minor.revision ideas.
          * storage_protocol
              The protocol used to connect to the storage, this should be a short
              string such as: "iSCSI", "FC", "nfs", "ceph", etc.
          * total_capacity_gb
              The total capacity in gigabytes (GiB) of the storage backend being
              used to store Cinder volumes. Use keyword 'unknown' if the backend
              cannot report the value or 'infinite' if there is no upper limit.
              But, it is recommended to report real values as the Cinder
              scheduler assigns lowest weight to any storage backend reporting
              'unknown' or 'infinite'.
  
          * free_capacity_gb
              The free capacity in gigabytes (GiB). Use keyword 'unknown' if the
              backend cannot report the value or 'infinite' if there is no upper
              limit. But, it is recommended to report real values as the Cinder
              scheduler assigns lowest weight to any storage backend reporting
              'unknown' or 'infinite'.
  
          And the following optional fields:
  
          * reserved_percentage (integer)
              Percentage of backend capacity which is not used by the scheduler.
          * location_info (string)
              Driver-specific information used by the driver and storage backend
              to correlate Cinder volumes and backend LUNs/files.
          * QoS_support (Boolean)
              Whether the backend supports quality of service.
          * provisioned_capacity_gb
              The total provisioned capacity on the storage backend, in gigabytes
              (GiB), including space consumed by any user other than Cinder
              itself.
          * max_over_subscription_ratio
              The maximum amount a backend can be over subscribed.
          * thin_provisioning_support (Boolean)
              Whether the backend is capable of allocating thinly provisioned
              volumes.
          * thick_provisioning_support (Boolean)
              Whether the backend is capable of allocating thick provisioned
              volumes. (Typically True.)
          * total_volumes (integer)
              Total number of volumes on the storage backend. This can be used in
              custom driver filter functions.
          * filter_function (string)
              A custom function used by the scheduler to determine whether a
              volume should be allocated to this backend or not. Example:
  
                capabilities.total_volumes < 10
  
          * goodness_function (string)
              Similar to filter_function, but used to weigh multiple volume
              backends. Example:
  
                capabilities.capacity_utilization < 0.6 ? 100 : 25
  
          * multiattach (Boolean)
              Whether the backend supports multiattach or not. Defaults to False.
          * sparse_copy_volume (Boolean)
              Whether copies performed by the volume manager for operations such
              as migration should attempt to preserve sparseness.
  
          The returned dict may also contain a list, "pools", which has a similar
          dict for each pool being used with the backend.
  
          :param refresh: Whether to discard any cached values and force a full
                          refresh of stats.
          :returns: dict of appropriate values (see above).
          """
  
      def create_volume(self, volume):
          """Create a new volume on the backend.
  
          This method is responsible only for storage allocation on the backend.
          It should not export a LUN or actually make this storage available for
          use, this is done in a later call.
  
          # TODO(smcginnis) - Add example data structure of volume object.
          :param volume: Volume object containing specifics to create.
          :returns: (Optional) dict of database updates for the new volume.
          :raises: VolumeBackendAPIException if creation failed.
          """
  
      def delete_volume(self, volume):
          """Delete a volume from the backend.
  
          If the driver can talk to the backend and detects that the volume is no
          longer present, this call should succeed and allow Cinder to complete
          the process of deleting the volume.
  
          :param volume: The volume to delete.
          :raises: VolumeIsBusy if the volume is still attached or has snapshots.
                   VolumeBackendAPIException on error.
          """
  
      def initialize_connection(self, volume, connector, initiator_data=None):
          """Allow connection to connector and return connection info.
  
          :param volume: The volume to be attached.
          :param connector: Dictionary containing information about what is being
                            connected to.
          :param initiator_data: (Optional) A dictionary of driver_initiator_data
                                 objects with key-value pairs that have been
                                 saved for this initiator by a driver in previous
                                 initialize_connection calls.
          :returns: A dictionary of connection information. This can optionally
                    include a "initiator_updates" field.
  
          The "initiator_updates" field must be a dictionary containing a
          "set_values" and/or "remove_values" field. The "set_values" field must
          be a dictionary of key-value pairs to be set/updated in the db. The
          "remove_values" field must be a list of keys, previously set with
          "set_values", that will be deleted from the db.
  
          May be called multiple times to get connection information after a
          volume has already been attached.
          """
  
      def attach_volume(self, context, volume, instance_uuid, host_name,
                        mountpoint):
          """Lets the driver know Nova has attached the volume to an instance.
  
          :param context: Security/policy info for the request.
          :param volume: Volume being attached.
          :param instance_uuid: ID of the instance being attached to.
          :param host_name: The host name.
          :param mountpoint: Device mount point on the instance.
          """
  
      def terminate_connection(self, volume, connector):
          """Remove access to a volume.
  
          :param volume: The volume to remove.
          :param connector: The Dictionary containing information about the
                            connection.
          """
  
      def detach_volume(self, context, volume, attachment=None):
          """Detach volume from an instance.
  
          :param context: Security/policy info for the request.
          :param volume: Volume being detached.
          :param attachment: (Optional) Attachment information.
          """
  
      def clone_image(self, volume, image_location, image_id, image_metadata,
                      image_service):
          """Clone an image to a volume.
  
          :param volume: The volume to create.
          :param image_location: Where to pull the image from.
          :param image_id: The image identifier.
          :param image_metadata: Information about the image.
          :param image_service: The image service to use.
          :returns: Model updates.
          """
  
      def copy_image_to_volume(self, context, volume, image_service, image_id):
          """Fetch the image from image_service and write it to the volume.
  
          :param context: Security/policy info for the request.
          :param volume: The volume to create.
          :param image_service: The image service to use.
          :param image_id: The image identifier.
          :returns: Model updates.
          """
  
      def copy_volume_to_image(self, context, volume, image_service, image_meta):
          """Copy the volume to the specified image.
  
          :param context: Security/policy info for the request.
          :param volume: The volume to copy.
          :param image_service: The image service to use.
          :param image_meta: Information about the image.
          :returns: Model updates.
          """
  
      def extend_volume(self, volume, new_size):
          """Extend the size of a volume.
  
          :param volume: The volume to extend.
          :param new_size: The new desired size of the volume.
          """
  