text: #    Copyright 2013 IBM Corp.
  #
  #    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.
  
  """Nova common internal object model"""
  
  import collections
  import contextlib
  import copy
  import datetime
  import functools
  import traceback
  
  import netaddr
  from oslo import messaging
  from oslo.utils import timeutils
  import six
  
  from nova import context
  from nova import exception
  from nova.i18n import _, _LE
  from nova import objects
  from nova.objects import fields
  from nova.openstack.common import log as logging
  from nova.openstack.common import versionutils
  from nova import utils
  
  
  LOG = logging.getLogger('object')
  
  
  class NotSpecifiedSentinel:
      pass
  
  
  def get_attrname(name):
      """Return the mangled name of the attribute's underlying storage."""
      return '_' + name
  
  
  def make_class_properties(cls):
      # NOTE(danms/comstud): Inherit fields from super classes.
      # mro() returns the current class first and returns 'object' last, so
      # those can be skipped.  Also be careful to not overwrite any fields
      # that already exist.  And make sure each cls has its own copy of
      # fields and that it is not sharing the dict with a super class.
      cls.fields = dict(cls.fields)
      for supercls in cls.mro()[1:-1]:
          if not hasattr(supercls, 'fields'):
              continue
          for name, field in supercls.fields.items():
              if name not in cls.fields:
                  cls.fields[name] = field
      for name, field in cls.fields.iteritems():
          if not isinstance(field, fields.Field):
              raise exception.ObjectFieldInvalid(
                  field=name, objname=cls.obj_name())
  
          def getter(self, name=name):
              attrname = get_attrname(name)
              if not hasattr(self, attrname):
                  self.obj_load_attr(name)
              return getattr(self, attrname)
  
          def setter(self, value, name=name, field=field):
              attrname = get_attrname(name)
              field_value = field.coerce(self, name, value)
              if field.read_only and hasattr(self, attrname):
                  # Note(yjiang5): _from_db_object() may iterate
                  # every field and write, no exception in such situation.
                  if getattr(self, attrname) != field_value:
                      raise exception.ReadOnlyFieldError(field=name)
                  else:
                      return
  
              self._changed_fields.add(name)
              try:
                  return setattr(self, attrname, field_value)
              except Exception:
                  attr = "%s.%s" % (self.obj_name(), name)
                  LOG.exception(_LE('Error setting %(attr)s'), {'attr': attr})
                  raise
  
          setattr(cls, name, property(getter, setter))
  
  
  class NovaObjectMetaclass(type):
      """Metaclass that allows tracking of object classes."""
  
      # NOTE(danms): This is what controls whether object operations are
      # remoted. If this is not None, use it to remote things over RPC.
      indirection_api = None
  
      def __init__(cls, names, bases, dict_):
          if not hasattr(cls, '_obj_classes'):
              # This means this is a base class using the metaclass. I.e.,
              # the 'NovaObject' class.
              cls._obj_classes = collections.defaultdict(list)
              return
  
          def _vers_tuple(obj):
              return tuple([int(x) for x in obj.VERSION.split(".")])
  
          # Add the subclass to NovaObject._obj_classes. If the
          # same version already exists, replace it. Otherwise,
          # keep the list with newest version first.
          make_class_properties(cls)
          obj_name = cls.obj_name()
          for i, obj in enumerate(cls._obj_classes[obj_name]):
              if cls.VERSION == obj.VERSION:
                  cls._obj_classes[obj_name][i] = cls
                  # Update nova.objects with this newer class.
                  setattr(objects, obj_name, cls)
                  break
              if _vers_tuple(cls) > _vers_tuple(obj):
                  # Insert before.
                  cls._obj_classes[obj_name].insert(i, cls)
                  if i == 0:
                      # Later version than we've seen before. Update
                      # nova.objects.
                      setattr(objects, obj_name, cls)
                  break
          else:
              cls._obj_classes[obj_name].append(cls)
              # Either this is the first time we've seen the object or it's
              # an older version than anything we'e seen. Update nova.objects
              # only if it's the first time we've seen this object name.
              if not hasattr(objects, obj_name):
                  setattr(objects, obj_name, cls)
  
  
  # These are decorators that mark an object's method as remotable.
  # If the metaclass is configured to forward object methods to an
  # indirection service, these will result in making an RPC call
  # instead of directly calling the implementation in the object. Instead,
  # the object implementation on the remote end will perform the
  # requested action and the result will be returned here.
  def remotable_classmethod(fn):
      """Decorator for remotable classmethods."""
      @functools.wraps(fn)
      def wrapper(cls, context, *args, **kwargs):
          if NovaObject.indirection_api:
              result = NovaObject.indirection_api.object_class_action(
                  context, cls.obj_name(), fn.__name__, cls.VERSION,
                  args, kwargs)
          else:
              result = fn(cls, context, *args, **kwargs)
              if isinstance(result, NovaObject):
                  result._context = context
          return result
  
      # NOTE(danms): Make this discoverable
      wrapper.remotable = True
      wrapper.original_fn = fn
      return classmethod(wrapper)
  
  
  # See comment above for remotable_classmethod()
  #
  # Note that this will use either the provided context, or the one
  # stashed in the object. If neither are present, the object is
  # "orphaned" and remotable methods cannot be called.
  def remotable(fn):
      """Decorator for remotable object methods."""
      @functools.wraps(fn)
      def wrapper(self, *args, **kwargs):
          ctxt = self._context
          try:
              if isinstance(args[0], (context.RequestContext)):
                  ctxt = args[0]
                  args = args[1:]
          except IndexError:
              pass
          if ctxt is None:
              raise exception.OrphanedObjectError(method=fn.__name__,
                                                  objtype=self.obj_name())
          # Force this to be set if it wasn't before.
          self._context = ctxt
          if NovaObject.indirection_api:
              updates, result = NovaObject.indirection_api.object_action(
                  ctxt, self, fn.__name__, args, kwargs)
              for key, value in updates.iteritems():
                  if key in self.fields:
                      field = self.fields[key]
                      # NOTE(ndipanov): Since NovaObjectSerializer will have
                      # deserialized any object fields into objects already,
                      # we do not try to deserialize them again here.
                      if isinstance(value, NovaObject):
                          self[key] = value
                      else:
                          self[key] = field.from_primitive(self, key, value)
              self.obj_reset_changes()
              self._changed_fields = set(updates.get('obj_what_changed', []))
              return result
          else:
              return fn(self, ctxt, *args, **kwargs)
  
      wrapper.remotable = True
      wrapper.original_fn = fn
      return wrapper
  
  
  @six.add_metaclass(NovaObjectMetaclass)
  class NovaObject(object):
      """Base class and object factory.
  
      This forms the base of all objects that can be remoted or instantiated
      via RPC. Simply defining a class that inherits from this base class
      will make it remotely instantiatable. Objects should implement the
      necessary "get" classmethod routines as well as "save" object methods
      as appropriate.
      """
  
      # Object versioning rules
      #
      # Each service has its set of objects, each with a version attached. When
      # a client attempts to call an object method, the server checks to see if
      # the version of that object matches (in a compatible way) its object
      # implementation. If so, cool, and if not, fail.
      #
      # This version is allowed to have three parts, X.Y.Z, where the .Z element
      # is reserved for stable branch backports. The .Z is ignored for the
      # purposes of triggering a backport, which means anything changed under
      # a .Z must be additive and non-destructive such that a node that knows
      # about X.Y can consider X.Y.Z equivalent.
      VERSION = '1.0'
  
      # The fields present in this object as key:field pairs. For example:
      #
      # fields = { 'foo': fields.IntegerField(),
      #            'bar': fields.StringField(),
      #          }
      fields = {}
      obj_extra_fields = []
  
      # Table of sub-object versioning information
      #
      # This contains a list of version mappings, by the field name of
      # the subobject. The mappings must be in order of oldest to
      # newest, and are tuples of (my_version, subobject_version). A
      # request to backport this object to $my_version will cause the
      # subobject to be backported to $subobject_version.
      #
      # obj_relationships = {
      #     'subobject1': [('1.2', '1.1'), ('1.4', '1.2')],
      #     'subobject2': [('1.2', '1.0')],
      # }
      #
      # In the above example:
      #
      # - If we are asked to backport our object to version 1.3,
      #   subobject1 will be backported to version 1.1, since it was
      #   bumped to version 1.2 when our version was 1.4.
      # - If we are asked to backport our object to version 1.5,
      #   no changes will be made to subobject1 or subobject2, since
      #   they have not changed since version 1.4.
      # - If we are asked to backlevel our object to version 1.1, we
      #   will remove both subobject1 and subobject2 from the primitive,
      #   since they were not added until version 1.2.
      obj_relationships = {}
  
      def __init__(self, context=None, **kwargs):
          self._changed_fields = set()
          self._context = context
          for key in kwargs.keys():
              setattr(self, key, kwargs[key])
  
      def __repr__(self):
          return '%s(%s)' % (
              self.obj_name(),
              ','.join(['%s=%s' % (name,
                                   (self.obj_attr_is_set(name) and
                                    field.stringify(getattr(self, name)) or
                                    '<?>'))
                        for name, field in sorted(self.fields.items())]))
  
      @classmethod
      def obj_name(cls):
          """Return a canonical name for this object which will be used over
          the wire for remote hydration.
          """
          return cls.__name__
  
      @classmethod
      def obj_class_from_name(cls, objname, objver):
          """Returns a class from the registry based on a name and version."""
          if objname not in cls._obj_classes:
              LOG.error(_LE('Unable to instantiate unregistered object type '
                            '%(objtype)s'), dict(objtype=objname))
              raise exception.UnsupportedObjectError(objtype=objname)
  
          # NOTE(comstud): If there's not an exact match, return the highest
          # compatible version. The objects stored in the class are sorted
          # such that highest version is first, so only set compatible_match
          # once below.
          compatible_match = None
  
          for objclass in cls._obj_classes[objname]:
              if objclass.VERSION == objver:
                  return objclass
              if (not compatible_match and
                      versionutils.is_compatible(objver, objclass.VERSION)):
                  compatible_match = objclass
  
          if compatible_match:
              return compatible_match
  
          # As mentioned above, latest version is always first in the list.
          latest_ver = cls._obj_classes[objname][0].VERSION
          raise exception.IncompatibleObjectVersion(objname=objname,
                                                    objver=objver,
                                                    supported=latest_ver)
  
      @classmethod
      def _obj_from_primitive(cls, context, objver, primitive):
          self = cls()
          self._context = context
          self.VERSION = objver
          objdata = primitive['nova_object.data']
          changes = primitive.get('nova_object.changes', [])
          for name, field in self.fields.items():
              if name in objdata:
                  setattr(self, name, field.from_primitive(self, name,
                                                           objdata[name]))
          self._changed_fields = set([x for x in changes if x in self.fields])
          return self
  
      @classmethod
      def obj_from_primitive(cls, primitive, context=None):
          """Object field-by-field hydration."""
          if primitive['nova_object.namespace'] != 'nova':
              # NOTE(danms): We don't do anything with this now, but it's
              # there for "the future"
              raise exception.UnsupportedObjectError(
                  objtype='%s.%s' % (primitive['nova_object.namespace'],
                                     primitive['nova_object.name']))
          objname = primitive['nova_object.name']
          objver = primitive['nova_object.version']
          objclass = cls.obj_class_from_name(objname, objver)
          return objclass._obj_from_primitive(context, objver, primitive)
  
      def __deepcopy__(self, memo):
          """Efficiently make a deep copy of this object."""
  
          # NOTE(danms): A naive deepcopy would copy more than we need,
          # and since we have knowledge of the volatile bits of the
          # object, we can be smarter here. Also, nested entities within
          # some objects may be uncopyable, so we can avoid those sorts
          # of issues by copying only our field data.
  
          nobj = self.__class__()
          nobj._context = self._context
          for name in self.fields:
              if self.obj_attr_is_set(name):
                  nval = copy.deepcopy(getattr(self, name), memo)
                  setattr(nobj, name, nval)
          nobj._changed_fields = set(self._changed_fields)
          return nobj
  
      def obj_clone(self):
          """Create a copy."""
          return copy.deepcopy(self)
  
      def _obj_make_obj_compatible(self, primitive, target_version, field):
          """Backlevel a sub-object based on our versioning rules.
  
          This is responsible for backporting objects contained within
          this object's primitive according to a set of rules we
          maintain about version dependencies between objects. This
          requires that the obj_relationships table in this object is
          correct and up-to-date.
  
          :param:primitive: The primitive version of this object
          :param:target_version: The version string requested for this object
          :param:field: The name of the field in this object containing the
                        sub-object to be backported
          """
  
          def _do_backport(to_version):
              obj = getattr(self, field)
              if not obj:
                  return
              if isinstance(obj, NovaObject):
                  obj.obj_make_compatible(
                      primitive[field]['nova_object.data'],
                      to_version)
                  primitive[field]['nova_object.version'] = to_version
              elif isinstance(obj, list):
                  for i, element in enumerate(obj):
                      element.obj_make_compatible(
                          primitive[field][i]['nova_object.data'],
                          to_version)
                      primitive[field][i]['nova_object.version'] = to_version
  
          target_version = utils.convert_version_to_tuple(target_version)
          for index, versions in enumerate(self.obj_relationships[field]):
              my_version, child_version = versions
              my_version = utils.convert_version_to_tuple(my_version)
              if target_version < my_version:
                  if index == 0:
                      # We're backporting to a version from before this
                      # subobject was added: delete it from the primitive.
                      del primitive[field]
                  else:
                      # We're in the gap between index-1 and index, so
                      # backport to the older version
                      last_child_version = \
                          self.obj_relationships[field][index - 1][1]
                      _do_backport(last_child_version)
                  return
              elif target_version == my_version:
                  # This is the first mapping that satisfies the
                  # target_version request: backport the object.
                  _do_backport(child_version)
                  return
  
      def obj_make_compatible(self, primitive, target_version):
          """Make an object representation compatible with a target version.
  
          This is responsible for taking the primitive representation of
          an object and making it suitable for the given target_version.
          This may mean converting the format of object attributes, removing
          attributes that have been added since the target version, etc. In
          general:
  
          - If a new version of an object adds a field, this routine
            should remove it for older versions.
          - If a new version changed or restricted the format of a field, this
            should convert it back to something a client knowing only of the
            older version will tolerate.
          - If an object that this object depends on is bumped, then this
            object should also take a version bump. Then, this routine should
            backlevel the dependent object (by calling its obj_make_compatible())
            if the requested version of this object is older than the version
            where the new dependent object was added.
  
          :param:primitive: The result of self.obj_to_primitive()
          :param:target_version: The version string requested by the recipient
          of the object
          :raises: nova.exception.UnsupportedObjectError if conversion
          is not possible for some reason
          """
          for key, field in self.fields.items():
              if not isinstance(field, (fields.ObjectField,
                                        fields.ListOfObjectsField)):
                  continue
              if not self.obj_attr_is_set(key):
                  continue
              if key not in self.obj_relationships:
                  # NOTE(danms): This is really a coding error and shouldn't
                  # happen unless we miss something
                  raise exception.ObjectActionError(
                      action='obj_make_compatible',
                      reason='No rule for %s' % key)
              self._obj_make_obj_compatible(primitive, target_version, key)
  
      def obj_to_primitive(self, target_version=None):
          """Simple base-case dehydration.
  
          This calls to_primitive() for each item in fields.
          """
          primitive = dict()
          for name, field in self.fields.items():
              if self.obj_attr_is_set(name):
                  primitive[name] = field.to_primitive(self, name,
                                                       getattr(self, name))
          if target_version:
              self.obj_make_compatible(primitive, target_version)
          obj = {'nova_object.name': self.obj_name(),
                 'nova_object.namespace': 'nova',
                 'nova_object.version': target_version or self.VERSION,
                 'nova_object.data': primitive}
          if self.obj_what_changed():
              obj['nova_object.changes'] = list(self.obj_what_changed())
          return obj
  
      def obj_set_defaults(self, *attrs):
          if not attrs:
              attrs = [name for name, field in self.fields.items()
                       if field.default != fields.UnspecifiedDefault]
  
          for attr in attrs:
              default = self.fields[attr].default
              if default is fields.UnspecifiedDefault:
                  raise exception.ObjectActionError(
                      action='set_defaults',
                      reason='No default set for field %s' % attr)
              setattr(self, attr, default)
  
      def obj_load_attr(self, attrname):
          """Load an additional attribute from the real object.
  
          This should use self._conductor, and cache any data that might
          be useful for future load operations.
          """
          raise NotImplementedError(
              _("Cannot load '%s' in the base class") % attrname)
  
      def save(self, context):
          """Save the changed fields back to the store.
  
          This is optional for subclasses, but is presented here in the base
          class for consistency among those that do.
          """
          raise NotImplementedError('Cannot save anything in the base class')
  
      def obj_what_changed(self):
          """Returns a set of fields that have been modified."""
          changes = set(self._changed_fields)
          for field in self.fields:
              if (self.obj_attr_is_set(field) and
                      isinstance(getattr(self, field), NovaObject) and
                      getattr(self, field).obj_what_changed()):
                  changes.add(field)
          return changes
  
      def obj_get_changes(self):
          """Returns a dict of changed fields and their new values."""
          changes = {}
          for key in self.obj_what_changed():
              changes[key] = getattr(self, key)
          return changes
  
      def obj_reset_changes(self, fields=None):
          """Reset the list of fields that have been changed.
  
          Note that this is NOT "revert to previous values"
          """
          if fields:
              self._changed_fields -= set(fields)
          else:
              self._changed_fields.clear()
  
      def obj_attr_is_set(self, attrname):
          """Test object to see if attrname is present.
  
          Returns True if the named attribute has a value set, or
          False if not. Raises AttributeError if attrname is not
          a valid attribute for this object.
          """
          if attrname not in self.obj_fields:
              raise AttributeError(
                  _("%(objname)s object has no attribute '%(attrname)s'") %
                  {'objname': self.obj_name(), 'attrname': attrname})
          return hasattr(self, get_attrname(attrname))
  
      @property
      def obj_fields(self):
          return self.fields.keys() + self.obj_extra_fields
  
  
  class NovaObjectDictCompat(object):
      """Mix-in to provide dictionary key access compat
  
      If an object needs to support attribute access using
      dictionary items instead of object attributes, inherit
      from this class. This should only be used as a temporary
      measure until all callers are converted to use modern
      attribute access.
  
      NOTE(berrange) This class will eventually be deleted.
      """
  
      # dictish syntactic sugar
      def iteritems(self):
          """For backwards-compatibility with dict-based objects.
  
          NOTE(danms): May be removed in the future.
          """
          for name in self.obj_fields:
              if (self.obj_attr_is_set(name) or
                      name in self.obj_extra_fields):
                  yield name, getattr(self, name)
  
      items = lambda self: list(self.iteritems())
  
      def __getitem__(self, name):
          """For backwards-compatibility with dict-based objects.
  
          NOTE(danms): May be removed in the future.
          """
          return getattr(self, name)
  
      def __setitem__(self, name, value):
          """For backwards-compatibility with dict-based objects.
  
          NOTE(danms): May be removed in the future.
          """
          setattr(self, name, value)
  
      def __contains__(self, name):
          """For backwards-compatibility with dict-based objects.
  
          NOTE(danms): May be removed in the future.
          """
          try:
              return self.obj_attr_is_set(name)
          except AttributeError:
              return False
  
      def get(self, key, value=NotSpecifiedSentinel):
          """For backwards-compatibility with dict-based objects.
  
          NOTE(danms): May be removed in the future.
          """
          if key not in self.obj_fields:
              raise AttributeError("'%s' object has no attribute '%s'" % (
                      self.__class__, key))
          if value != NotSpecifiedSentinel and not self.obj_attr_is_set(key):
              return value
          else:
              return getattr(self, key)
  
      def update(self, updates):
          """For backwards-compatibility with dict-base objects.
  
          NOTE(danms): May be removed in the future.
          """
          for key, value in updates.items():
              setattr(self, key, value)
  
  
  class NovaPersistentObject(object):
      """Mixin class for Persistent objects.
      This adds the fields that we use in common for all persistent objects.
      """
      fields = {
          'created_at': fields.DateTimeField(nullable=True),
          'updated_at': fields.DateTimeField(nullable=True),
          'deleted_at': fields.DateTimeField(nullable=True),
          'deleted': fields.BooleanField(default=False),
          }
  
      @contextlib.contextmanager
      def obj_as_admin(self):
          """Context manager to make an object call as an admin.
  
          This temporarily modifies the context embedded in an object to
          be elevated() and restores it after the call completes. Example
          usage:
  
             with obj.obj_as_admin():
                 obj.save()
  
          """
          if self._context is None:
              raise exception.OrphanedObjectError(method='obj_as_admin',
                                                  objtype=self.obj_name())
  
          original_context = self._context
          self._context = self._context.elevated()
          try:
              yield
          finally:
              self._context = original_context
  
  
  class ObjectListBase(object):
      """Mixin class for lists of objects.
  
      This mixin class can be added as a base class for an object that
      is implementing a list of objects. It adds a single field of 'objects',
      which is the list store, and behaves like a list itself. It supports
      serialization of the list of objects automatically.
      """
      fields = {
          'objects': fields.ListOfObjectsField('NovaObject'),
          }
  
      # This is a dictionary of my_version:child_version mappings so that
      # we can support backleveling our contents based on the version
      # requested of the list object.
      child_versions = {}
  
      def __init__(self, *args, **kwargs):
          super(ObjectListBase, self).__init__(*args, **kwargs)
          if 'objects' not in kwargs:
              self.objects = []
              self._changed_fields.discard('objects')
  
      def __iter__(self):
          """List iterator interface."""
          return iter(self.objects)
  
      def __len__(self):
          """List length."""
          return len(self.objects)
  
      def __getitem__(self, index):
          """List index access."""
          if isinstance(index, slice):
              new_obj = self.__class__()
              new_obj.objects = self.objects[index]
              # NOTE(danms): We must be mixed in with a NovaObject!
              new_obj.obj_reset_changes()
              new_obj._context = self._context
              return new_obj
          return self.objects[index]
  
      def __contains__(self, value):
          """List membership test."""
          return value in self.objects
  
      def count(self, value):
          """List count of value occurrences."""
          return self.objects.count(value)
  
      def index(self, value):
          """List index of value."""
          return self.objects.index(value)
  
      def sort(self, cmp=None, key=None, reverse=False):
          self.objects.sort(cmp=cmp, key=key, reverse=reverse)
  
      def obj_make_compatible(self, primitive, target_version):
          primitives = primitive['objects']
          child_target_version = self.child_versions.get(target_version, '1.0')
          for index, item in enumerate(self.objects):
              self.objects[index].obj_make_compatible(
                  primitives[index]['nova_object.data'],
                  child_target_version)
              primitives[index]['nova_object.version'] = child_target_version
  
      def obj_what_changed(self):
          changes = set(self._changed_fields)
          for child in self.objects:
              if child.obj_what_changed():
                  changes.add('objects')
          return changes
  
  
  class NovaObjectSerializer(messaging.NoOpSerializer):
      """A NovaObject-aware Serializer.
  
      This implements the Oslo Serializer interface and provides the
      ability to serialize and deserialize NovaObject entities. Any service
      that needs to accept or return NovaObjects as arguments or result values
      should pass this to its RPCClient and RPCServer objects.
      """
  
      @property
      def conductor(self):
          if not hasattr(self, '_conductor'):
              from nova import conductor
              self._conductor = conductor.API()
          return self._conductor
  
      def _process_object(self, context, objprim):
          try:
              objinst = NovaObject.obj_from_primitive(objprim, context=context)
          except exception.IncompatibleObjectVersion as e:
              objver = objprim['nova_object.version']
              if objver.count('.') == 2:
                  # NOTE(danms): For our purposes, the .z part of the version
                  # should be safe to accept without requiring a backport
                  objprim['nova_object.version'] = \
                      '.'.join(objver.split('.')[:2])
                  return self._process_object(context, objprim)
              objinst = self.conductor.object_backport(context, objprim,
                                                       e.kwargs['supported'])
          return objinst
  
      def _process_iterable(self, context, action_fn, values):
          """Process an iterable, taking an action on each value.
          :param:context: Request context
          :param:action_fn: Action to take on each item in values
          :param:values: Iterable container of things to take action on
          :returns: A new container of the same type (except set) with
                    items from values having had action applied.
          """
          iterable = values.__class__
          if issubclass(iterable, dict):
              return iterable(**dict((k, action_fn(context, v))
                              for k, v in six.iteritems(values)))
          else:
              # NOTE(danms): A set can't have an unhashable value inside, such as
              # a dict. Convert sets to tuples, which is fine, since we can't
              # send them over RPC anyway.
              if iterable == set:
                  iterable = tuple
              return iterable([action_fn(context, value) for value in values])
  
      def serialize_entity(self, context, entity):
          if isinstance(entity, (tuple, list, set, dict)):
              entity = self._process_iterable(context, self.serialize_entity,
                                              entity)
          elif (hasattr(entity, 'obj_to_primitive') and
                callable(entity.obj_to_primitive)):
              entity = entity.obj_to_primitive()
          return entity
  
      def deserialize_entity(self, context, entity):
          if isinstance(entity, dict) and 'nova_object.name' in entity:
              entity = self._process_object(context, entity)
          elif isinstance(entity, (tuple, list, set, dict)):
              entity = self._process_iterable(context, self.deserialize_entity,
                                              entity)
          return entity
  
  
  def obj_to_primitive(obj):
      """Recursively turn an object into a python primitive.
  
      A NovaObject becomes a dict, and anything that implements ObjectListBase
      becomes a list.
      """
      if isinstance(obj, ObjectListBase):
          return [obj_to_primitive(x) for x in obj]
      elif isinstance(obj, NovaObject):
          result = {}
          for key in obj.obj_fields:
              if obj.obj_attr_is_set(key) or key in obj.obj_extra_fields:
                  result[key] = obj_to_primitive(getattr(obj, key))
          return result
      elif isinstance(obj, netaddr.IPAddress):
          return str(obj)
      elif isinstance(obj, netaddr.IPNetwork):
          return str(obj)
      else:
          return obj
  
  
  def obj_make_list(context, list_obj, item_cls, db_list, **extra_args):
      """Construct an object list from a list of primitives.
  
      This calls item_cls._from_db_object() on each item of db_list, and
      adds the resulting object to list_obj.
  
      :param:context: Request context
      :param:list_obj: An ObjectListBase object
      :param:item_cls: The NovaObject class of the objects within the list
      :param:db_list: The list of primitives to convert to objects
      :param:extra_args: Extra arguments to pass to _from_db_object()
      :returns: list_obj
      """
      list_obj.objects = []
      for db_item in db_list:
          item = item_cls._from_db_object(context, item_cls(), db_item,
                                          **extra_args)
          list_obj.objects.append(item)
      list_obj._context = context
      list_obj.obj_reset_changes()
      return list_obj
  
  
  def serialize_args(fn):
      """Decorator that will do the arguments serialization before remoting."""
      def wrapper(obj, *args, **kwargs):
          for kw in kwargs:
              value_arg = kwargs.get(kw)
              if kw == 'exc_val' and value_arg:
                  kwargs[kw] = str(value_arg)
              elif kw == 'exc_tb' and (
                      not isinstance(value_arg, six.string_types) and value_arg):
                  kwargs[kw] = ''.join(traceback.format_tb(value_arg))
              elif isinstance(value_arg, datetime.datetime):
                  kwargs[kw] = timeutils.isotime(value_arg)
          if hasattr(fn, '__call__'):
              return fn(obj, *args, **kwargs)
          # NOTE(danms): We wrap a descriptor, so use that protocol
          return fn.__get__(None, obj)(*args, **kwargs)
  
      # NOTE(danms): Make this discoverable
      wrapper.remotable = getattr(fn, 'remotable', False)
      wrapper.original_fn = fn
      return (functools.wraps(fn)(wrapper) if hasattr(fn, '__call__')
              else classmethod(wrapper))
  