# Copyright (c) 2023 NetApp, Inc. All rights reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.
"""
Volume driver library for NetApp C-mode NVMe storage systems.
"""

import uuid

from oslo_log import log as logging
from oslo_utils import excutils
from oslo_utils import units

from cinder import coordination
from cinder import exception
from cinder.i18n import _
from cinder.objects import fields
from cinder.volume.drivers.netapp.dataontap.client import api as netapp_api
from cinder.volume.drivers.netapp.dataontap.performance import perf_cmode
from cinder.volume.drivers.netapp.dataontap.utils import capabilities
from cinder.volume.drivers.netapp.dataontap.utils import loopingcalls
from cinder.volume.drivers.netapp.dataontap.utils import utils as dot_utils
from cinder.volume.drivers.netapp import options as na_opts
from cinder.volume.drivers.netapp import utils as na_utils
from cinder.volume import volume_utils

LOG = logging.getLogger(__name__)


class NetAppNamespace(object):
    """Represents a namespace on NetApp storage."""

    def __init__(self, handle, name, size, metadata_dict):
        self.handle = handle
        self.name = name
        self.size = size
        self.metadata = metadata_dict or {}

    def get_metadata_property(self, prop):
        """Get the metadata property of a namespace."""
        if prop in self.metadata:
            return self.metadata[prop]
        name = self.name
        LOG.debug("No metadata property %(prop)s defined for the namespace "
                  "%(name)s", {'prop': prop, 'name': name})

    def __str__(self, *args, **kwargs):
        return ('NetApp namespace [handle:%s, name:%s, size:%s, metadata:%s]'
                % (self.handle, self.name, self.size, self.metadata))


class NetAppNVMeStorageLibrary(
        object, metaclass=volume_utils.TraceWrapperMetaclass):
    """NetApp NVMe storage library for Data ONTAP."""

    # do not increment this as it may be used in volume type definitions.
    VERSION = "1.0.0"
    REQUIRED_FLAGS_BASIC = ['netapp_login', 'netapp_password',
                            'netapp_server_hostname']
    REQUIRED_FLAGS_CERT = ['netapp_private_key_file',
                           'netapp_certificate_file']
    ALLOWED_NAMESPACE_OS_TYPES = ['aix', 'linux', 'vmware', 'windows']
    ALLOWED_SUBSYSTEM_HOST_TYPES = ['aix', 'linux', 'vmware', 'windows']
    DEFAULT_NAMESPACE_OS = 'linux'
    DEFAULT_HOST_TYPE = 'linux'
    DEFAULT_FILTER_FUNCTION = 'capabilities.utilization < 70'
    DEFAULT_GOODNESS_FUNCTION = '100 - capabilities.utilization'
    REQUIRED_CMODE_FLAGS = ['netapp_vserver']
    NVME_PORT = 4420
    NVME_TRANSPORT = "tcp"

    def __init__(self, driver_name, driver_protocol, **kwargs):

        na_utils.validate_instantiation(**kwargs)

        self.driver_name = driver_name
        self.driver_protocol = driver_protocol
        self.rest_client = None
        self._stats = {}
        self.namespace_table = {}
        self.namespace_ostype = None
        self.host_type = None
        self.app_version = kwargs.get("app_version", "unknown")
        self.host = kwargs.get('host')
        self.backend_name = self.host.split('@')[1]

        self.configuration = kwargs['configuration']
        self.configuration.append_config_values(na_opts.netapp_connection_opts)
        self.configuration.append_config_values(na_opts.netapp_basicauth_opts)
        self.configuration.append_config_values(
            na_opts.netapp_certificateauth_opts)
        self.configuration.append_config_values(na_opts.netapp_transport_opts)
        self.configuration.append_config_values(
            na_opts.netapp_provisioning_opts)
        self.configuration.append_config_values(na_opts.netapp_san_opts)
        self.configuration.append_config_values(na_opts.netapp_cluster_opts)

        self.max_over_subscription_ratio = (
            volume_utils.get_max_over_subscription_ratio(
                self.configuration.max_over_subscription_ratio,
                supports_auto=True))
        self.reserved_percentage = self.configuration.reserved_percentage
        self.loopingcalls = loopingcalls.LoopingCalls()

    def do_setup(self, context):
        if self.configuration.netapp_private_key_file or\
                self.configuration.netapp_certificate_file:
            na_utils.check_flags(self.REQUIRED_FLAGS_CERT,
                                 self.configuration)
        else:
            na_utils.check_flags(self.REQUIRED_FLAGS_BASIC,
                                 self.configuration)
        self.namespace_ostype = (self.configuration.netapp_namespace_ostype
                                 or self.DEFAULT_NAMESPACE_OS)
        self.host_type = (self.configuration.netapp_host_type
                          or self.DEFAULT_HOST_TYPE)

        na_utils.check_flags(self.REQUIRED_CMODE_FLAGS, self.configuration)

        # NOTE(felipe_rodrigues): NVMe driver is only available with
        # REST client.
        self.client = dot_utils.get_client_for_backend(
            self.backend_name, force_rest=True)
        self.vserver = self.client.vserver

        # Storage service catalog.
        self.ssc_library = capabilities.CapabilitiesLibrary(
            self.driver_protocol, self.vserver, self.client,
            self.configuration)

        self.ssc_library.check_api_permissions()

        self.using_cluster_credentials = (
            self.ssc_library.cluster_user_supported())

        # Performance monitoring library.
        self.perf_library = perf_cmode.PerformanceCmodeLibrary(
            self.client)

    def _update_ssc(self):
        """Refresh the storage service catalog with the latest set of pools."""

        """Refresh the storage service catalog with the latest set of pools."""
        if self.configuration.netapp_disaggregated_platform:
            self.ssc_library.update_ssc_asa(self._get_cluster_to_pool_map())
        else:
            self.ssc_library.update_ssc(self._get_flexvol_to_pool_map())

    def _get_flexvol_to_pool_map(self):
        """Get the flexvols that match the pool name search pattern.

        The map is of the format suitable for seeding the storage service
        catalog: {<flexvol_name> : {'pool_name': <flexvol_name>}}
        """

        pool_regex = na_utils.get_pool_name_filter_regex(self.configuration)

        pools = {}
        flexvol_names = self.client.list_flexvols()

        for flexvol_name in flexvol_names:

            msg_args = {
                'flexvol': flexvol_name,
                'vol_pattern': pool_regex.pattern,
            }

            if pool_regex.match(flexvol_name):
                msg = "Volume '%(flexvol)s' matches %(vol_pattern)s"
                LOG.debug(msg, msg_args)
                pools[flexvol_name] = {'pool_name': flexvol_name}
            else:
                msg = "Volume '%(flexvol)s' does not match %(vol_pattern)s"
                LOG.debug(msg, msg_args)

        return pools

    def _get_cluster_to_pool_map(self):
        return dot_utils.get_cluster_to_pool_map(self.client)

    def check_for_setup_error(self):
        """Check that the driver is working and can communicate.

        Discovers the namespaces on the NetApp server.
        """
        if (not self.configuration.netapp_disaggregated_platform
                and not self._get_flexvol_to_pool_map()):
            msg = _('No pools are available for provisioning volumes. '
                    'Ensure that the configuration option '
                    'netapp_pool_name_search_pattern is set correctly.')
            raise na_utils.NetAppDriverException(msg)
        elif self.configuration.netapp_disaggregated_platform:
            if not self._get_cluster_to_pool_map():
                msg = _('No pools are available for provisioning volumes. '
                        'Ensure ASA r2 configuration option is set correctly.')
                raise na_utils.NetAppDriverException(msg)
        self._add_looping_tasks()

        if self.namespace_ostype not in self.ALLOWED_NAMESPACE_OS_TYPES:
            msg = _("Invalid value for NetApp configuration"
                    " option netapp_namespace_ostype.")
            LOG.error(msg)
            raise na_utils.NetAppDriverException(msg)
        if self.host_type not in self.ALLOWED_SUBSYSTEM_HOST_TYPES:
            msg = _("Invalid value for NetApp configuration"
                    " option netapp_host_type.")
            LOG.error(msg)
            raise na_utils.NetAppDriverException(msg)

        namespace_list = self.client.get_namespace_list()
        self._extract_and_populate_namespaces(namespace_list)
        LOG.debug("Success getting list of namespace from server.")

        self.loopingcalls.start_tasks()

    def _add_looping_tasks(self):
        """Add tasks that need to be executed at a fixed interval.

        Inheriting class overrides and then explicitly calls this method.
        """
        # Note(cknight): Run the update once in the current thread to prevent a
        # race with the first invocation of _update_volume_stats.
        self._update_ssc()

        # Add the task that updates the slow-changing storage service catalog.
        self.loopingcalls.add_task(self._update_ssc,
                                   loopingcalls.ONE_HOUR,
                                   loopingcalls.ONE_HOUR)

        # Add the task that logs EMS messages.
        self.loopingcalls.add_task(
            self._handle_ems_logging,
            loopingcalls.ONE_HOUR)

    def _handle_ems_logging(self):
        """Log autosupport messages."""

        base_ems_message = dot_utils.build_ems_log_message_0(
            self.driver_name, self.app_version)
        self.client.send_ems_log_message(base_ems_message)

        pool_ems_message = dot_utils.build_ems_log_message_1(
            self.driver_name, self.app_version, self.vserver,
            self.ssc_library.get_ssc_flexvol_names(), [])
        self.client.send_ems_log_message(pool_ems_message)

    def get_pool(self, volume):
        """Return pool name where volume resides.

        :param volume: The volume hosted by the driver.
        :return: Name of the pool where given volume is hosted.
        """
        name = volume['name']
        metadata = self._get_namespace_attr(name, 'metadata') or dict()
        return metadata.get('Volume', None)

    def create_volume(self, volume):
        """Driver entry point for creating a new volume (ONTAP namespace)."""

        LOG.debug('create_volume on %s', volume['host'])

        # get Data ONTAP volume name as pool name.
        pool_name = volume_utils.extract_host(volume['host'], level='pool')
        if pool_name is None:
            msg = _("Pool is not available in the volume host field.")
            raise exception.InvalidHost(reason=msg)

        namespace = volume.name
        size = int(volume['size']) * units.Gi
        metadata = {'OsType': self.namespace_ostype,
                    'Path': '/vol/%s/%s' % (pool_name, namespace)}

        if self.configuration.netapp_disaggregated_platform:
            namespace = na_utils.get_backend_lun_or_ns_name(
                namespace,
                self.configuration,
            )
            # For ASAr2 path name is same as namespace name
            metadata = {'OsType': self.namespace_ostype,
                        'Path': namespace}
        try:
            self.client.create_namespace(pool_name, namespace, size, metadata)
        except Exception:
            LOG.exception("Exception creating namespace %(name)s in pool "
                          "%(pool)s.", {'name': namespace, 'pool': pool_name})
            msg = _("Volume %s could not be created.")
            raise exception.VolumeBackendAPIException(data=msg % namespace)
        LOG.debug('Created namespace with name %(name)s.', {'name': namespace})

        metadata['Volume'] = pool_name
        metadata['Qtree'] = None
        handle = self._create_namespace_handle(metadata)
        self._add_namespace_to_table(
            NetAppNamespace(handle, namespace, size, metadata))

        return

    def delete_volume(self, volume):
        """Driver entry point for destroying existing volumes."""
        self._delete_namespace(volume['name'])

    def _delete_namespace(self, namespace_name):
        """Helper method to delete namespace backing a volume or snapshot."""
        namespace_name = na_utils.get_backend_lun_or_ns_name(
            namespace_name,
            self.configuration,
        )
        metadata = self._get_namespace_attr(namespace_name, 'metadata')
        if metadata:
            try:
                self.client.destroy_namespace(metadata['Path'])
            except netapp_api.NaApiError as e:
                if e.code in netapp_api.REST_NAMESPACE_EOBJECTNOTFOUND:
                    LOG.warning("Failure deleting namespace %(name)s. "
                                "%(message)s",
                                {'name': namespace_name, 'message': e})
                else:
                    error_message = (_('A NetApp Api Error occurred: %s') % e)
                    raise na_utils.NetAppDriverException(error_message)
            self.namespace_table.pop(namespace_name)
        else:
            LOG.warning("No entry in namespace table for volume/snapshot"
                        " %(name)s.", {'name': namespace_name})

    def ensure_export(self, context, volume):
        """Driver entry point to get the export info for an existing volume."""
        handle = self._get_namespace_attr(volume['name'], 'handle')
        return {'provider_location': handle}

    def create_export(self, context, volume):
        """Driver entry point to get the export info for a new volume."""
        handle = self._get_namespace_attr(volume['name'], 'handle')
        return {'provider_location': handle}

    def remove_export(self, context, volume):
        """Driver entry point to remove an export for a volume.

        Since exporting is idempotent in this driver, we have nothing
        to do for unexporting.
        """

        pass

    def create_snapshot(self, snapshot):
        """Driver entry point for creating a snapshot.

        This driver implements snapshots by using efficient single-file
        (namespace) cloning.
        """
        self._create_snapshot(snapshot)

    def _create_snapshot(self, snapshot):
        vol_name = snapshot['volume_name']
        snapshot_name = snapshot['name']
        namespace = self._get_namespace_from_table(vol_name)
        self._clone_namespace(namespace.name, snapshot_name)

    def _clone_namespace(self, name, new_name):
        """Clone namespace with the given handle to the new name."""
        metadata = self._get_namespace_attr(name, 'metadata')
        volume = metadata['Volume']

        self.client.clone_namespace(volume, name, new_name)

        LOG.debug("Cloned namespace with new name %s", new_name)
        namespace = self.client.get_namespace_by_args(
            vserver=self.vserver, path=f'/vol/{volume}/{new_name}')
        if len(namespace) == 0:
            msg = _("No cloned namespace named %s found on the filer.")
            raise exception.VolumeBackendAPIException(data=msg % new_name)

        cloned_namespace = namespace[0]
        self._add_namespace_to_table(
            NetAppNamespace(
                f"{cloned_namespace['Vserver']}:{cloned_namespace['Path']}",
                new_name,
                cloned_namespace['Size'],
                cloned_namespace))

    def delete_snapshot(self, snapshot):
        """Driver entry point for deleting a snapshot."""
        self._delete_namespace(snapshot['name'])
        LOG.debug("Snapshot %s deletion successful.", snapshot['name'])

    def create_volume_from_snapshot(self, volume, snapshot):
        source = {'name': snapshot['name'], 'size': snapshot['volume_size']}
        self._clone_source_to_destination(source, volume)

    def create_cloned_volume(self, volume, src_vref):
        src_namespace = self._get_namespace_from_table(src_vref['name'])
        source = {'name': src_namespace.name, 'size': src_vref['size']}
        self._clone_source_to_destination(source, volume)

    def _clone_source_to_destination(self, source, destination_volume):
        source_size = source['size']
        destination_size = destination_volume['size']

        source_name = source['name']
        destination_name = destination_volume['name']

        try:
            self._clone_namespace(source_name, destination_name)

            if destination_size != source_size:

                try:
                    self._extend_volume(destination_volume, destination_size)
                except Exception:
                    with excutils.save_and_reraise_exception():
                        LOG.error("Resizing %s failed. Cleaning volume.",
                                  destination_volume['id'])
                        self.delete_volume(destination_volume)

        except Exception:
            LOG.exception("Exception cloning volume %(name)s from source "
                          "volume %(source)s.",
                          {'name': destination_name, 'source': source_name})

            msg = _("Volume %s could not be created from source volume.")
            raise exception.VolumeBackendAPIException(
                data=msg % destination_name)

    def _create_namespace_handle(self, metadata):
        """Returns namespace handle based on filer type."""
        return '%s:%s' % (self.vserver, metadata['Path'])

    def _extract_namespace_info(self, namespace):
        """Extracts the namespace from API and populates the table."""

        path = namespace['Path']
        if self.configuration.netapp_disaggregated_platform:
            name = path
        else:
            (_rest, _splitter, name) = path.rpartition('/')

        handle = self._create_namespace_handle(namespace)
        size = namespace['Size']
        return NetAppNamespace(handle, name, size, namespace)

    def _extract_and_populate_namespaces(self, api_namespaces):
        """Extracts the namespaces from API and populates the table."""

        for namespace in api_namespaces:
            discovered_namespace = self._extract_namespace_info(namespace)
            self._add_namespace_to_table(discovered_namespace)

    def _add_namespace_to_table(self, namespace):
        """Adds namespace to cache table."""
        if not isinstance(namespace, NetAppNamespace):
            msg = _("Object is not a NetApp namespace.")
            raise exception.VolumeBackendAPIException(data=msg)
        self.namespace_table[namespace.name] = namespace

    def _get_namespace_from_table(self, name):
        """Gets namespace from cache table.

        Refreshes cache if namespace not found in cache.
        """
        name = na_utils.get_backend_lun_or_ns_name(name, self.configuration)
        namespace = self.namespace_table.get(name)
        if namespace is None:
            namespace_list = self.client.get_namespace_list()
            self._extract_and_populate_namespaces(namespace_list)
            namespace = self.namespace_table.get(name)
            if namespace is None:
                raise exception.VolumeNotFound(volume_id=name)
        return namespace

    def _get_namespace_attr(self, name, attr):
        """Get the namespace attribute if found else None."""
        try:
            attr = getattr(self._get_namespace_from_table(name), attr)
            return attr
        except exception.VolumeNotFound as e:
            LOG.error("Message: %s", e.msg)
        except Exception as e:
            LOG.error("Error getting namespace attribute. Exception: %s", e)
        return None

    def get_volume_stats(self, refresh=False, filter_function=None,
                         goodness_function=None):
        """Get volume stats.

        If 'refresh' is True, update the stats first.
        """

        if refresh:
            self._update_volume_stats(filter_function=filter_function,
                                      goodness_function=goodness_function)
        return self._stats

    def _update_volume_stats(self, filter_function=None,
                             goodness_function=None):
        """Retrieve backend stats."""

        LOG.debug('Updating volume stats')
        data = {}
        backend_name = self.configuration.safe_get('volume_backend_name')
        data['volume_backend_name'] = backend_name or self.driver_name
        data['vendor_name'] = 'NetApp'
        data['driver_version'] = self.VERSION
        data['storage_protocol'] = self.driver_protocol
        data['pools'] = self._get_pool_stats(
            filter_function=filter_function,
            goodness_function=goodness_function)
        data['sparse_copy_volume'] = True
        data['replication_enabled'] = False

        self._stats = data

    def _get_pool_stats(self, filter_function=None, goodness_function=None):
        """Retrieve pool (Data ONTAP flexvol) stats.

        Pool statistics are assembled from static driver capabilities, the
        Storage Service Catalog of flexvol attributes, and real-time capacity
        and controller utilization metrics.  The pool name is the flexvol name.
        """

        pools = []

        ssc = self.ssc_library.get_ssc()
        if not ssc:
            return pools

        # Utilization and performance metrics require cluster-scoped
        # credentials
        if (self.using_cluster_credentials
                and not self.configuration.netapp_disaggregated_platform):
            # Get up-to-date node utilization metrics just once
            self.perf_library.update_performance_cache(ssc)

            # Get up-to-date aggregate capacities just once
            aggregates = self.ssc_library.get_ssc_aggregates()
            aggr_capacities = self.client.get_aggregate_capacities(
                aggregates)
        else:
            aggr_capacities = {}

        for ssc_vol_name, ssc_vol_info in ssc.items():

            pool = dict()

            # Add storage service catalog data
            pool.update(ssc_vol_info)

            # Add driver capabilities and config info
            pool['QoS_support'] = False
            pool['multiattach'] = True
            pool['online_extend_support'] = True
            pool['consistencygroup_support'] = True
            pool['consistent_group_snapshot_enabled'] = True
            pool['reserved_percentage'] = self.reserved_percentage
            pool['max_over_subscription_ratio'] = (
                self.max_over_subscription_ratio)

            # Add up-to-date capacity info
            if self.configuration.netapp_disaggregated_platform:
                capacity = self.client.get_cluster_capacity()
            else:
                capacity = self.client.get_flexvol_capacity(
                    flexvol_name=ssc_vol_name)

            size_total_gb = capacity['size-total'] / units.Gi
            pool['total_capacity_gb'] = na_utils.round_down(size_total_gb)

            size_available_gb = capacity['size-available'] / units.Gi
            pool['free_capacity_gb'] = na_utils.round_down(size_available_gb)

            namespaces = self.client.get_namespace_sizes_by_volume(
                ssc_vol_name)
            pool['total_volumes'] = len(namespaces)
            if self.configuration.netapp_driver_reports_provisioned_capacity:
                provisioned_cap = 0
                for namespace in namespaces:
                    namespace_name = namespace['path'].split('/')[-1]
                    # Filtering namespaces that matches the volume name
                    # template to exclude snapshots.
                    if volume_utils.extract_id_from_volume_name(
                            namespace_name):
                        provisioned_cap = provisioned_cap + namespace['size']
                pool['provisioned_capacity_gb'] = na_utils.round_down(
                    float(provisioned_cap) / units.Gi)

            if (self.using_cluster_credentials and
                    not self.configuration.netapp_disaggregated_platform):
                dedupe_used = self.client.get_flexvol_dedupe_used_percent(
                    ssc_vol_name)
            else:
                dedupe_used = 0.0
            pool['netapp_dedupe_used_percent'] = na_utils.round_down(
                dedupe_used)

            aggregate_name = ssc_vol_info.get('netapp_aggregate')
            aggr_capacity = aggr_capacities.get(aggregate_name, {})
            pool['netapp_aggregate_used_percent'] = aggr_capacity.get(
                'percent-used', 0)

            # Add utilization data
            utilization = self.perf_library.get_node_utilization_for_pool(
                ssc_vol_name)
            pool['utilization'] = na_utils.round_down(utilization)
            pool['filter_function'] = filter_function
            pool['goodness_function'] = goodness_function

            pools.append(pool)

        return pools

    def get_default_filter_function(self):
        """Get the default filter_function string."""
        return self.DEFAULT_FILTER_FUNCTION

    def get_default_goodness_function(self):
        """Get the default goodness_function string."""
        return self.DEFAULT_GOODNESS_FUNCTION

    def extend_volume(self, volume, new_size):
        """Driver entry point to increase the size of a volume."""
        self._extend_volume(volume, new_size)

    def _extend_volume(self, volume, new_size):
        """Extend an existing volume to the new size."""
        name = na_utils.get_backend_lun_or_ns_name(volume['name'],
                                                   self.configuration)
        namespace = self._get_namespace_from_table(name)
        path = namespace.metadata['Path']
        curr_size_bytes = str(namespace.size)
        new_size_bytes = str(int(new_size) * units.Gi)
        # Reused by clone scenarios.
        # Hence comparing the stored size.
        if curr_size_bytes == new_size_bytes:
            LOG.info("No need to extend volume %s"
                     " as it is already the requested new size.", name)
            return

        self.client.namespace_resize(path, new_size_bytes)

        self.namespace_table[name].size = new_size_bytes

    def _find_mapped_namespace_subsystem(self, path, host_nqn):
        """Find an subsystem for a namespace mapped to the given host."""
        subsystems = [subsystem['name'] for subsystem in
                      self.client.get_subsystem_by_host(host_nqn)]

        # Map subsystem name to namespace-id for the requested host.
        namespace_map = {v['uuid']: (v['subsystem_uuid'], v['subsystem'])
                         for v in self.client.get_namespace_map(path)
                         if v['subsystem'] in subsystems}

        subsystem_uuid = subsystem_name = n_uuid = None
        # Give preference to OpenStack subsystems, just use the last one if not
        # present to allow unmapping old mappings that used a custom subsystem.
        for n_uuid, (subsystem_uuid, subsystem_name) in namespace_map.items():
            if subsystem_name.startswith(na_utils.OPENSTACK_PREFIX):
                break

        return subsystem_uuid, subsystem_name, n_uuid

    def _map_namespace(self, name, host_nqn):
        """Maps namespace to the host nqn and returns its ID assigned."""
        metadata = self._get_namespace_attr(name, 'metadata')
        path = metadata['Path']
        try:
            subsystems = self.client.get_namespace_map(path)
            ns_uuid = subsystem_uuid = None
            if subsystems:
                subsystem_name = subsystems[0]['subsystem']
                subsystem_uuid = subsystems[0]['subsystem_uuid']
                ns_uuid = subsystems[0]['uuid']
                self.client.map_host_with_subsystem(host_nqn, subsystem_uuid)
            else:
                subsystem_name = na_utils.OPENSTACK_PREFIX + str(uuid.uuid4())
                self.client.create_subsystem(subsystem_name, self.host_type,
                                             host_nqn)
                ns_uuid = self.client.map_namespace(path, subsystem_name, )
            return subsystem_name, ns_uuid
        except netapp_api.NaApiError as e:
            (_, subsystem_name, ns_uuid) =\
                self._find_mapped_namespace_subsystem(
                path, host_nqn)
            if ns_uuid is not None and subsystem_name:
                return subsystem_name, ns_uuid
            else:
                raise e

    def initialize_connection(self, volume, connector):
        """Initializes the connection and returns connection info.

        Assign any created volume to a compute node/host so that it can be
        used from that host. Example return values:

        .. code-block:: default

            {
                'driver_volume_type': 'nvmeof',
                'data': {
                    'target_nqn' 'nqn.1992-01.example.com:subsystem',
                    'host_nqn': 'nqn.1992-01.example.com:string',
                    'portals': [
                        ('10.10.10.10', '4420', 'tcp')
                    ],
                    'uuid': 'a1129e6f-8497-4c0c-be01-3eab1ba684ed'
                }
            }

        """
        host_nqn = connector.get("nqn")
        if not host_nqn:
            raise exception.VolumeBackendAPIException(
                data=_("Initialize connection error: no host nqn available!"))

        name = volume['name']
        subsystem, namespace_uuid = self._map_namespace(name, host_nqn)

        LOG.debug("Mapped namespace %(name)s to the host NQN %(host_nqn)s",
                  {'name': name, 'host_nqn': host_nqn})

        target_nqn = self.client.get_nvme_subsystem_nqn(subsystem)
        if not target_nqn:
            msg = _('Failed to get subsystem %(subsystem)s target NQN for the '
                    'namespace %(name)s')
            msg_args = {'subsystem': subsystem, 'name': name}
            raise exception.VolumeBackendAPIException(data=msg % msg_args)

        target_portals = self.client.get_nvme_target_portals()
        if not target_portals:
            msg = _('Failed to get target portals for the namespace %s')
            raise exception.VolumeBackendAPIException(
                data=msg % name)

        portal = (target_portals[0], self.NVME_PORT, self.NVME_TRANSPORT)
        data = {
            "target_nqn": str(target_nqn),
            "host_nqn": host_nqn,
            "portals": [portal],
            "vol_uuid": namespace_uuid
        }
        conn_info = {"driver_volume_type": "nvmeof", "data": data}
        LOG.debug("Initialize connection info: %s", conn_info)

        return conn_info

    def _unmap_namespace(self, path, host_nqn):
        """Unmaps a namespace from given host."""

        if not host_nqn:
            LOG.warning("Nothing to unmap - host_nqn is missing: %s", path)
            return

        (subsystem_uuid, _, _) = self._find_mapped_namespace_subsystem(
            path, host_nqn)

        if subsystem_uuid:
            self.client.unmap_host_with_subsystem(host_nqn, subsystem_uuid)
        else:
            LOG.debug("No mapping exists between namespace: %s"
                      " and host_nqn: %s", path, host_nqn)

    @coordination.synchronized('netapp-terminate-nvme-connection-{volume.id}')
    def terminate_connection(self, volume, connector, **kwargs):
        """Driver entry point to unattach a volume from an instance.

        Unmask the namespace on the storage system so the given initiator can
        no longer access it.
        """

        if connector and na_utils.is_multiattach_to_host(
                volume,
                connector
        ):
            return
        name = volume['name']
        host_nqn = None
        if connector is None:
            LOG.debug('Unmapping namespace %(name)s from all hosts.',
                      {'name': name})
        else:
            host_nqn = connector.get("nqn")
            LOG.debug("Unmapping namespace %(name)s from the host "
                      "%(host_nqn)s", {'name': name, 'host_nqn': host_nqn})

        metadata = self._get_namespace_attr(name, 'metadata')
        path = metadata['Path']
        self._unmap_namespace(path, host_nqn)

    def create_group(self, group):
        """Driver entry point for creating a generic volume group.

        ONTAP does not maintain an actual Group construct. As a result, no
        communication to the backend is necessary for generic volume group
        creation.

        :returns: Hard-coded model update for generic volume group model.
        """
        model_update = {'status': fields.GroupStatus.AVAILABLE}
        return model_update

    def delete_group(self, group, volumes):
        """Driver entry point for deleting a group.

        :returns: Updated group model and list of volume models
                 for the volumes that were deleted.
        """
        model_update = {'status': fields.GroupStatus.DELETED}
        volumes_model_update = []
        for volume in volumes:
            try:
                self.delete_volume(volume)
                volumes_model_update.append(
                    {'id': volume['id'], 'status': 'deleted'})
            except Exception:
                volumes_model_update.append(
                    {'id': volume['id'],
                     'status': 'error_deleting'})
                LOG.exception("Volume %(vol)s in the group could not be "
                              "deleted.", {'vol': volume})
        return model_update, volumes_model_update

    def update_group(self, group, add_volumes=None, remove_volumes=None):
        """Driver entry point for updating a generic volume group.

        Since no actual group construct is ever created in ONTAP, it is not
        necessary to update any metadata on the backend. Since this is a NO-OP,
        there is guaranteed to be no change in any of the volumes' statuses.
        """
        return None, None, None

    def create_group_snapshot(self, group_snapshot, snapshots):
        """Creates a Cinder group snapshot object.

        The Cinder group snapshot object is created by making use of an
        ephemeral ONTAP consistency group snapshot in order to provide
        write-order consistency for a set of flexvol snapshots. First, a list
        of the flexvols backing the given Cinder group must be gathered. An
        ONTAP group-snapshot of these flexvols will create a snapshot copy of
        all the Cinder volumes in the generic volume group. For each Cinder
        volume in the group, it is then necessary to clone its backing
        namespace from the ONTAP cg-snapshot. The naming convention used for
        the clones is what indicates the clone's role as a Cinder snapshot
        and its inclusion in a Cinder group. The ONTAP cg-snapshot of the
        flexvols is no longer required after having cloned the namespaces
        backing the Cinder volumes in the Cinder group.

        :returns: An implicit update for group snapshot and snapshots models
                 that is interpreted by the manager to set their models to
                 available.
        """
        try:
            if volume_utils.is_group_a_cg_snapshot_type(group_snapshot):
                self._create_consistent_group_snapshot(group_snapshot,
                                                       snapshots)
            else:
                for snapshot in snapshots:
                    self._create_snapshot(snapshot)
        except Exception as ex:
            err_msg = (_("Create group snapshot failed (%s).") % ex)
            LOG.exception(err_msg, resource=group_snapshot)
            raise na_utils.NetAppDriverException(err_msg)

        return None, None

    def _create_consistent_group_snapshot(self, group_snapshot, snapshots):
        flexvols = set()
        for snapshot in snapshots:
            flexvols.add(volume_utils.extract_host(
                snapshot['volume']['host'], level='pool'))

        self.client.create_cg_snapshot(flexvols, group_snapshot['id'])

        for snapshot in snapshots:
            self._clone_namespace(snapshot['volume']['name'], snapshot['name'])

        for flexvol in flexvols:
            try:
                self.client.wait_for_busy_snapshot(
                    flexvol, group_snapshot['id'])
                self.client.delete_snapshot(
                    flexvol, group_snapshot['id'])
            except exception.SnapshotIsBusy:
                self.client.mark_snapshot_for_deletion(
                    flexvol, group_snapshot['id'])

    def delete_group_snapshot(self, group_snapshot, snapshots):
        """Delete namespaces backing each snapshot in the group snapshot.

        :returns: An implicit update for snapshots models that is interpreted
                 by the manager to set their models to delete.
        """
        for snapshot in snapshots:
            self._delete_namespace(snapshot['name'])
            LOG.debug("Snapshot %s deletion successful", snapshot['name'])

        return None, None

    def create_group_from_src(self, group, volumes, group_snapshot=None,
                              snapshots=None, source_group=None,
                              source_vols=None):
        """Creates a group from a group snapshot or a group of cinder vols.

        :returns: An implicit update for the volumes model that is
                 interpreted by the manager as a successful operation.
        """
        LOG.debug("VOLUMES %s ", ', '.join([vol['id'] for vol in volumes]))
        volume_model_updates = []

        if group_snapshot:
            vols = zip(volumes, snapshots)

            for volume, snapshot in vols:
                source = {
                    'name': snapshot['name'],
                    'size': snapshot['volume_size'],
                }
                self._clone_source_to_destination(source, volume)
                '''if volume_model_update is not None:
                    volume_model_update['id'] = volume['id']
                    volume_model_updates.append(volume_model_update)'''

        else:
            vols = zip(volumes, source_vols)

            for volume, old_src_vref in vols:
                src_namespace = self._get_namespace_from_table(
                    old_src_vref['name'])
                source = {'name': src_namespace.name,
                          'size': old_src_vref['size']}
                self._clone_source_to_destination(source, volume)
                '''if volume_model_update is not None:
                    volume_model_update['id'] = volume['id']
                    volume_model_updates.append(volume_model_update)'''

        return None, volume_model_updates
