xos/core/models/service.py

import json
from operator import attrgetter

from core.models import PlCoreBase, PlCoreBaseManager, SingletonModel, XOS
from core.models.plcorebase import StrippedCharField
from django.db import models
from xos.exceptions import *
import urlparse

COARSE_KIND = "coarse"

def get_xos():
    xos = XOS.objects.all()

    if xos:
       return xos[0]
    else:
       return None


class AttributeMixin(object):
    # helper for extracting things from a json-encoded
    # service_specific_attribute

    def get_attribute(self, name, default=None):
        if self.service_specific_attribute:
            attributes = json.loads(self.service_specific_attribute)
        else:
            attributes = {}
        return attributes.get(name, default)

    def set_attribute(self, name, value):
        if self.service_specific_attribute:
            attributes = json.loads(self.service_specific_attribute)
        else:
            attributes = {}
        attributes[name] = value
        self.service_specific_attribute = json.dumps(attributes)

    def get_initial_attribute(self, name, default=None):
        if self._initial["service_specific_attribute"]:
            attributes = json.loads(
                self._initial["service_specific_attribute"])
        else:
            attributes = {}
        return attributes.get(name, default)

    @classmethod
    def get_default_attribute(cls, name):
        for (attrname, default) in cls.simple_attributes:
            if attrname == name:
                return default
        if hasattr(cls, "default_attributes"):
            if name in cls.default_attributes:
                return cls.default_attributes[name]

        return None

    @classmethod
    def setup_simple_attributes(cls):
        for (attrname, default) in cls.simple_attributes:
            setattr(cls, attrname, property(lambda self, attrname=attrname, default=default: self.get_attribute(attrname, default),
                                            lambda self, value, attrname=attrname: self.set_attribute(
                                                attrname, value),
                                            None,
                                            attrname))

class ServiceController(PlCoreBase):
    xos = models.ForeignKey(XOS, related_name='service_controllers', help_text="Pointer to XOS", default=get_xos)
    name = StrippedCharField(max_length=30, help_text="Service Name")
    base_url = StrippedCharField(max_length=1024, help_text="Base URL, allows use of relative URLs for resources", null=True, blank=True)

    def __unicode__(self): return u'%s' % (self.name)

class ServiceControllerResource(PlCoreBase):
    KIND_CHOICES = (('models', 'Models'),
                    ('admin', 'Admin'),
                    ('django_library', 'Django Library'),
                    ('synchronizer', 'Synchronizer'),
                    ('rest', 'REST API'),
                    ('tosca_custom_types', 'Tosca Custom Types'),
                    ('tosca_resource', 'Tosca Resource'))

    FORMAT_CHOICES = (('python', 'Python'),
                      ('manifest', 'Manifest'),
                      ('docker', 'Docker Container'),
                      ('yaml', 'YAML'))

    service_controller = models.ForeignKey(ServiceController, related_name='service_controller_resources',
                                help_text="The Service Controller this resource is associated with")

    name = StrippedCharField(max_length=30, help_text="Object Name")
    kind = StrippedCharField(choices=KIND_CHOICES, max_length=30)
    format = StrippedCharField(choices=FORMAT_CHOICES, max_length=30)
    url = StrippedCharField(max_length=1024, help_text="URL of resource", null=True, blank=True)

    def __unicode__(self): return u'%s' % (self.name)

    @property
    def full_url(self):
        if self.service_controller and self.service_controller.base_url:
            return urlparse.urljoin(self.service_controller.base_url, self.url)
        else:
            return self.url

class Service(PlCoreBase, AttributeMixin):
    # when subclassing a service, redefine KIND to describe the new service
    KIND = "generic"

    description = models.TextField(
        max_length=254, null=True, blank=True, help_text="Description of Service")
    enabled = models.BooleanField(default=True)
    kind = StrippedCharField(
        max_length=30, help_text="Kind of service", default=KIND)
    name = StrippedCharField(max_length=30, help_text="Service Name")
    versionNumber = StrippedCharField(blank=True, null=True,
        max_length=30, help_text="Version of Service Definition")
    published = models.BooleanField(default=True)
    view_url = StrippedCharField(blank=True, null=True, max_length=1024)
    icon_url = StrippedCharField(blank=True, null=True, max_length=1024)
    public_key = models.TextField(
        null=True, blank=True, max_length=1024, help_text="Public key string")
    private_key_fn = StrippedCharField(blank=True, null=True, max_length=1024)

    # Service_specific_attribute and service_specific_id are opaque to XOS
    service_specific_id = StrippedCharField(
        max_length=30, blank=True, null=True)
    service_specific_attribute = models.TextField(blank=True, null=True)

    controller = models.ForeignKey(ServiceController, related_name='services',
                                help_text="The Service Controller this Service uses")

    def __init__(self, *args, **kwargs):
        # for subclasses, set the default kind appropriately
        self._meta.get_field("kind").default = self.KIND
        super(Service, self).__init__(*args, **kwargs)

    @classmethod
    def get_service_objects(cls):
        return cls.objects.filter(kind=cls.KIND)

    @classmethod
    def get_deleted_service_objects(cls):
        return cls.deleted_objects.filter(kind=cls.KIND)

    @classmethod
    def get_service_objects_by_user(cls, user):
        return cls.select_by_user(user).filter(kind=cls.KIND)

    @classmethod
    def select_by_user(cls, user):
        if user.is_admin:
            return cls.objects.all()
        else:
            service_ids = [
                sp.slice.id for sp in ServicePrivilege.objects.filter(user=user)]
            return cls.objects.filter(id__in=service_ids)

    @property
    def serviceattribute_dict(self):
        attrs = {}
        for attr in self.serviceattributes.all():
            attrs[attr.name] = attr.value
        return attrs

    def __unicode__(self): return u'%s' % (self.name)

    def can_update(self, user):
        return user.can_update_service(self, allow=['admin'])

    def get_scalable_nodes(self, slice, max_per_node=None, exclusive_slices=[]):
        """
             Get a list of nodes that can be used to scale up a slice.

                slice - slice to scale up
                max_per_node - maximum numbers of instances that 'slice' can have on a single node
                exclusive_slices - list of slices that must have no nodes in common with 'slice'.
        """

        # late import to get around order-of-imports constraint in __init__.py
        from core.models import Node, Instance

        nodes = list(Node.objects.all())

        conflicting_instances = Instance.objects.filter(
            slice__in=exclusive_slices)
        conflicting_nodes = Node.objects.filter(
            instances__in=conflicting_instances)

        nodes = [x for x in nodes if x not in conflicting_nodes]

        # If max_per_node is set, then limit the number of instances this slice
        # can have on a single node.
        if max_per_node:
            acceptable_nodes = []
            for node in nodes:
                existing_count = node.instances.filter(slice=slice).count()
                if existing_count < max_per_node:
                    acceptable_nodes.append(node)
            nodes = acceptable_nodes

        return nodes

    def pick_node(self, slice, max_per_node=None, exclusive_slices=[]):
        # Pick the best node to scale up a slice.

        nodes = self.get_scalable_nodes(slice, max_per_node, exclusive_slices)
        nodes = sorted(nodes, key=lambda node: node.instances.all().count())
        if not nodes:
            return None
        return nodes[0]

    def adjust_scale(self, slice_hint, scale, max_per_node=None, exclusive_slices=[]):
        # late import to get around order-of-imports constraint in __init__.py
        from core.models import Instance

        slices = [x for x in self.slices.all() if slice_hint in x.name]
        for slice in slices:
            while slice.instances.all().count() > scale:
                s = slice.instances.all()[0]
                # print "drop instance", s
                s.delete()

            while slice.instances.all().count() < scale:
                node = self.pick_node(slice, max_per_node, exclusive_slices)
                if not node:
                    # no more available nodes
                    break

                image = slice.default_image
                if not image:
                    raise XOSConfigurationError(
                        "No default_image for slice %s" % slice.name)

                flavor = slice.default_flavor
                if not flavor:
                    raise XOSConfigurationError(
                        "No default_flavor for slice %s" % slice.name)

                s = Instance(slice=slice,
                             node=node,
                             creator=slice.creator,
                             image=image,
                             flavor=flavor,
                             deployment=node.site_deployment.deployment)
                s.save()

                # print "add instance", s

    def get_vtn_src_nets(self):
        nets = []
        for slice in self.slices.all():
            for ns in slice.networkslices.all():
                if not ns.network:
                    continue
#                if ns.network.template.access in ["direct", "indirect"]:
#                    # skip access networks; we want to use the private network
#                    continue
                if "management" in ns.network.name:
                    # don't try to connect the management network to anything
                    continue
                if ns.network.name in ["wan_network", "lan_network"]:
                    # we don't want to attach to the vCPE's lan or wan network
                    # we only want to attach to its private network
                    # TODO: fix hard-coding of network name
                    continue
                for cn in ns.network.controllernetworks.all():
                    if cn.net_id:
                        net = {"name": ns.network.name, "net_id": cn.net_id}
                        nets.append(net)
        return nets

    def get_vtn_nets(self):
        nets = []
        for slice in self.slices.all():
            for ns in slice.networkslices.all():
                if not ns.network:
                    continue
                if ns.network.template.access not in ["direct", "indirect"]:
                    # skip anything that's not an access network
                    continue
                for cn in ns.network.controllernetworks.all():
                    if cn.net_id:
                        net = {"name": ns.network.name, "net_id": cn.net_id}
                        nets.append(net)
        return nets

    def get_vtn_dependencies_nets(self):
        provider_nets = []
        for tenant in self.subscribed_tenants.all():
            if tenant.provider_service:
                for net in tenant.provider_service.get_vtn_nets():
                    if not net in provider_nets:
                        provider_nets.append(net)
        return provider_nets

    def get_vtn_dependencies_ids(self):
        return [x["net_id"] for x in self.get_vtn_dependencies_nets()]

    def get_vtn_dependencies_names(self):
        return [x["name"] + "_" + x["net_id"] for x in self.get_vtn_dependencies_nets()]

    def get_vtn_src_ids(self):
        return [x["net_id"] for x in self.get_vtn_src_nets()]

    def get_vtn_src_names(self):
        return [x["name"] + "_" + x["net_id"] for x in self.get_vtn_src_nets()]


class ServiceAttribute(PlCoreBase):
    name = models.CharField(help_text="Attribute Name", max_length=128)
    value = StrippedCharField(help_text="Attribute Value", max_length=1024)
    service = models.ForeignKey(Service, related_name='serviceattributes',
                                help_text="The Service this attribute is associated with")


class ServiceRole(PlCoreBase):
    ROLE_CHOICES = (('admin', 'Admin'),)
    role = StrippedCharField(choices=ROLE_CHOICES, unique=True, max_length=30)

    def __unicode__(self): return u'%s' % (self.role)


class ServicePrivilege(PlCoreBase):
    user = models.ForeignKey('User', related_name='serviceprivileges')
    service = models.ForeignKey('Service', related_name='serviceprivileges')
    role = models.ForeignKey('ServiceRole', related_name='serviceprivileges')

    class Meta:
        unique_together = ('user', 'service', 'role')

    def __unicode__(self): return u'%s %s %s' % (
        self.service, self.user, self.role)

    def can_update(self, user):
        if not self.service.enabled:
            raise PermissionDenied, "Cannot modify permission(s) of a disabled service"
        return self.service.can_update(user)

    def save(self, *args, **kwds):
        if not self.service.enabled:
            raise PermissionDenied, "Cannot modify permission(s) of a disabled service"
        super(ServicePrivilege, self).save(*args, **kwds)

    def delete(self, *args, **kwds):
        if not self.service.enabled:
            raise PermissionDenied, "Cannot modify permission(s) of a disabled service"
        super(ServicePrivilege, self).delete(*args, **kwds)

    @classmethod
    def select_by_user(cls, user):
        if user.is_admin:
            qs = cls.objects.all()
        else:
            qs = cls.objects.filter(user=user)
        return qs


class TenantRoot(PlCoreBase, AttributeMixin):
    """ A tenantRoot is one of the things that can sit at the root of a chain
        of tenancy. This object represents a node.
    """

    KIND = "generic"
    kind = StrippedCharField(max_length=30, default=KIND)
    name = StrippedCharField(
        max_length=255, help_text="name", blank=True, null=True)

    service_specific_attribute = models.TextField(blank=True, null=True)
    service_specific_id = StrippedCharField(
        max_length=30, blank=True, null=True)

    def __init__(self, *args, **kwargs):
        # for subclasses, set the default kind appropriately
        self._meta.get_field("kind").default = self.KIND
        super(TenantRoot, self).__init__(*args, **kwargs)

    def __unicode__(self):
        if not self.name:
            return u"%s-tenant_root-#%s" % (str(self.kind), str(self.id))
        else:
            return self.name

    def can_update(self, user):
        return user.can_update_tenant_root(self, allow=['admin'])

    def get_subscribed_tenants(self, tenant_class):
        ids = self.subscribed_tenants.filter(kind=tenant_class.KIND)
        return tenant_class.objects.filter(id__in=ids)

    def get_newest_subscribed_tenant(self, kind):
        st = list(self.get_subscribed_tenants(kind))
        if not st:
            return None
        return sorted(st, key=attrgetter('id'))[0]

    @classmethod
    def get_tenant_objects(cls):
        return cls.objects.filter(kind=cls.KIND)

    @classmethod
    def get_tenant_objects_by_user(cls, user):
        return cls.select_by_user(user).filter(kind=cls.KIND)

    @classmethod
    def select_by_user(cls, user):
        if user.is_admin:
            return cls.objects.all()
        else:
            tr_ids = [
                trp.tenant_root.id for trp in TenantRootPrivilege.objects.filter(user=user)]
            return cls.objects.filter(id__in=tr_ids)

    # helper function to be used in subclasses that want to ensure
    # service_specific_id is unique
    def validate_unique_service_specific_id(self, none_okay=False):
        if not none_okay and (self.service_specific_id is None):
            raise XOSMissingField("subscriber_specific_id is None, and it's a required field", fields={
                                  "service_specific_id": "cannot be none"})

        if self.service_specific_id:
            conflicts = self.get_tenant_objects().filter(
                service_specific_id=self.service_specific_id)
            if self.pk:
                conflicts = conflicts.exclude(pk=self.pk)
            if conflicts:
                raise XOSDuplicateKey("service_specific_id %s already exists" % self.service_specific_id, fields={
                                      "service_specific_id": "duplicate key"})


class Tenant(PlCoreBase, AttributeMixin):
    """ A tenant is a relationship between two entities, a subscriber and a
        provider. This object represents an edge.

        The subscriber can be a User, a Service, or a Tenant.

        The provider is always a Service.

        TODO: rename "Tenant" to "Tenancy"
    """

    CONNECTIVITY_CHOICES = (('public', 'Public'),
                            ('private', 'Private'), ('na', 'Not Applicable'))

    # when subclassing a service, redefine KIND to describe the new service
    KIND = "generic"

    kind = StrippedCharField(max_length=30, default=KIND)
    provider_service = models.ForeignKey(
        Service, related_name='provided_tenants')

    # The next four things are the various type of objects that can be subscribers of this Tenancy
    # relationship. One and only one can be used at a time.
    # XXX these should really be changed to GenericForeignKey
    subscriber_service = models.ForeignKey(
        Service, related_name='subscribed_tenants', blank=True, null=True)
    subscriber_tenant = models.ForeignKey(
        "Tenant", related_name='subscribed_tenants', blank=True, null=True)
    subscriber_user = models.ForeignKey(
        "User", related_name='subscribed_tenants', blank=True, null=True)
    subscriber_root = models.ForeignKey(
        "TenantRoot", related_name="subscribed_tenants", blank=True, null=True)
    subscriber_network = models.ForeignKey(
        "Network", related_name="subscribed_tenants", blank=True, null=True)

    # Service_specific_attribute and service_specific_id are opaque to XOS
    service_specific_id = StrippedCharField(
        max_length=30, blank=True, null=True)
    service_specific_attribute = models.TextField(blank=True, null=True)

    # Connect_method is only used by Coarse tenants
    connect_method = models.CharField(
        null=False, blank=False, max_length=30, choices=CONNECTIVITY_CHOICES, default="na")

    def __init__(self, *args, **kwargs):
        # for subclasses, set the default kind appropriately
        self._meta.get_field("kind").default = self.KIND
        super(Tenant, self).__init__(*args, **kwargs)

    def __unicode__(self):
        return u"%s-tenant-%s" % (str(self.kind), str(self.id))

    @classmethod
    def get_tenant_objects(cls):
        return cls.objects.filter(kind=cls.KIND)

    @classmethod
    def get_tenant_objects_by_user(cls, user):
        return cls.select_by_user(user).filter(kind=cls.KIND)

    @classmethod
    def get_deleted_tenant_objects(cls):
        return cls.deleted_objects.filter(kind=cls.KIND)

    @property
    def tenantattribute_dict(self):
        attrs = {}
        for attr in self.tenantattributes.all():
            attrs[attr.name] = attr.value
        return attrs

    # helper function to be used in subclasses that want to ensure
    # service_specific_id is unique
    def validate_unique_service_specific_id(self):
        if self.pk is None:
            if self.service_specific_id is None:
                raise XOSMissingField("subscriber_specific_id is None, and it's a required field", fields={
                                      "service_specific_id": "cannot be none"})

            conflicts = self.get_tenant_objects().filter(
                service_specific_id=self.service_specific_id)
            if conflicts:
                raise XOSDuplicateKey("service_specific_id %s already exists" % self.service_specific_id, fields={
                                      "service_specific_id": "duplicate key"})

    def save(self, *args, **kwargs):
        subCount = sum([1 for e in [self.subscriber_service, self.subscriber_tenant,
                                    self.subscriber_user, self.subscriber_root] if e is not None])
        if (subCount > 1):
            raise XOSConflictingField(
                "Only one of subscriber_service, subscriber_tenant, subscriber_user, subscriber_root should be set")

        super(Tenant, self).save(*args, **kwargs)

    def get_subscribed_tenants(self, tenant_class):
        ids = self.subscribed_tenants.filter(kind=tenant_class.KIND)
        return tenant_class.objects.filter(id__in=ids)

    def get_newest_subscribed_tenant(self, kind):
        st = list(self.get_subscribed_tenants(kind))
        if not st:
            return None
        return sorted(st, key=attrgetter('id'))[0]


class Scheduler(object):
    # XOS Scheduler Abstract Base Class
    # Used to implement schedulers that pick which node to put instances on

    def __init__(self, slice):
        self.slice = slice

    def pick(self):
        # this method should return a tuple (node, parent)
        #    node is the node to instantiate on
        #    parent is for container_vm instances only, and is the VM that will
        #      hold the container

        raise Exception("Abstract Base")


class LeastLoadedNodeScheduler(Scheduler):
    # This scheduler always return the node with the fewest number of
    # instances.

    def __init__(self, slice, label=None):
        super(LeastLoadedNodeScheduler, self).__init__(slice)
        self.label = label

    def pick(self):
        from core.models import Node
        if not self.slice.default_node:
            nodes = list(Node.objects.all())
            nodes = sorted(nodes, key=lambda node: node.instances.all().count())
        else:
            nodes = list(Node.objects.filter(name = self.slice.default_node))

        if self.label:
            nodes = nodes.filter(nodelabels__name=self.label)

        nodes = list(nodes)

        if not nodes:
            raise Exception(
                "LeastLoadedNodeScheduler: No suitable nodes to pick from")

        # TODO: logic to filter nodes by which nodes are up, and which
        #   nodes the slice can instantiate on.
#        nodes = sorted(nodes, key=lambda node: node.instances.all().count())
        return [nodes[0], None]


class ContainerVmScheduler(Scheduler):
    # This scheduler picks a VM in the slice with the fewest containers inside
    # of it. If no VMs are suitable, then it creates a VM.

    MAX_VM_PER_CONTAINER = 10

    def __init__(self, slice):
        super(ContainerVmScheduler, self).__init__(slice)

    @property
    def image(self):
        from core.models import Image

        # If slice has default_image set then use it
        if self.slice.default_image:
            return self.slice.default_image

        raise XOPSProgrammingError("Please set a default image for %s" % self.slice.name)

    def make_new_instance(self):
        from core.models import Instance, Flavor

        flavors = Flavor.objects.filter(name="m1.small")
        if not flavors:
            raise XOSConfigurationError("No m1.small flavor")

        (node, parent) = LeastLoadedNodeScheduler(self.slice).pick()

        instance = Instance(slice=self.slice,
                            node=node,
                            image=self.image,
                            creator=self.slice.creator,
                            deployment=node.site_deployment.deployment,
                            flavor=flavors[0],
                            isolation="vm",
                            parent=parent)
        instance.save()
        # We rely on a special naming convention to identify the VMs that will
        # hole containers.
        instance.name = "%s-outer-%s" % (instance.slice.name, instance.id)
        instance.save()
        return instance

    def pick(self):
        from core.models import Instance, Flavor

        for vm in self.slice.instances.filter(isolation="vm"):
            avail_vms = []
            if (vm.name.startswith("%s-outer-" % self.slice.name)):
                container_count = Instance.objects.filter(parent=vm).count()
                if (container_count < self.MAX_VM_PER_CONTAINER):
                    avail_vms.append((vm, container_count))
            # sort by least containers-per-vm
            avail_vms = sorted(avail_vms, key=lambda x: x[1])
            print "XXX", avail_vms
            if avail_vms:
                instance = avail_vms[0][0]
                return (instance.node, instance)

        instance = self.make_new_instance()
        return (instance.node, instance)


class TenantWithContainer(Tenant):
    """ A tenant that manages a container """

    class Meta:
        proxy = True

    def __init__(self, *args, **kwargs):
        super(TenantWithContainer, self).__init__(*args, **kwargs)
        self.cached_instance = None
        self.orig_instance_id = self.get_initial_attribute("instance_id")

    @property
    def instance(self):
        from core.models import Instance
        if getattr(self, "cached_instance", None):
            return self.cached_instance
        instance_id = self.get_attribute("instance_id")
        if not instance_id:
            return None
        instances = Instance.objects.filter(id=instance_id)
        if not instances:
            return None
        instance = instances[0]
        instance.caller = self.creator
        self.cached_instance = instance
        return instance

    @instance.setter
    def instance(self, value):
        if value:
            value = value.id
        if (value != self.get_attribute("instance_id", None)):
            self.cached_instance = None
        self.set_attribute("instance_id", value)

    @property
    def external_hostname(self):
        return self.get_attribute("external_hostname", "")

    @external_hostname.setter
    def external_hostname(self, value):
        self.set_attribute("external_hostname", value)

    @property
    def external_container(self):
        return self.get_attribute("external_container", "")

    @external_container.setter
    def external_container(self, value):
        self.set_attribute("external_container", value)

    @property
    def creator(self):
        from core.models import User
        if getattr(self, "cached_creator", None):
            return self.cached_creator
        creator_id = self.get_attribute("creator_id")
        if not creator_id:
            return None
        users = User.objects.filter(id=creator_id)
        if not users:
            return None
        user = users[0]
        self.cached_creator = users[0]
        return user

    @creator.setter
    def creator(self, value):
        if value:
            value = value.id
        if (value != self.get_attribute("creator_id", None)):
            self.cached_creator = None
        self.set_attribute("creator_id", value)

    @property
    def image(self):
        from core.models import Image
        # Implement the logic here to pick the image that should be used when
        # instantiating the VM that will hold the container.

        slice = self.provider_service.slices.all()
        if not slice:
            raise XOSProgrammingError("provider service has no slice")
        slice = slice[0]

        # If slice has default_image set then use it
        if slice.default_image:
            return slice.default_image

        raise XOPSProgrammingError("Please set a default image for %s" % self.slice.name)

    def save_instance(self, instance):
        # Override this function to do custom pre-save or post-save processing,
        # such as creating ports for containers.
        instance.save()

    def pick_least_loaded_instance_in_slice(self, slices):
        for slice in slices:
            if slice.instances.all().count() > 0:
                for instance in slice.instances.all():
                    # Pick the first instance that has lesser than 5 tenants
                    if self.count_of_tenants_of_an_instance(instance) < 5:
                        return instance
        return None

    # TODO: Ideally the tenant count for an instance should be maintained using a
    # many-to-one relationship attribute, however this model being proxy, it does
    # not permit any new attributes to be defined. Find if any better solutions
    def count_of_tenants_of_an_instance(self, instance):
        tenant_count = 0
        for tenant in self.get_tenant_objects().all():
            if tenant.get_attribute("instance_id", None) == instance.id:
                tenant_count += 1
        return tenant_count

    def manage_container(self):
        from core.models import Instance, Flavor

        if self.deleted:
            return

        if (self.instance is not None) and (self.instance.image != self.image):
            self.instance.delete()
            self.instance = None

        if self.instance is None:
            if not self.provider_service.slices.count():
                raise XOSConfigurationError("The service has no slices")

            new_instance_created = False
            instance = None
            if self.get_attribute("use_same_instance_for_multiple_tenants", default=False):
                # Find if any existing instances can be used for this tenant
                slices = self.provider_service.slices.all()
                instance = self.pick_least_loaded_instance_in_slice(slices)

            if not instance:
                slice = self.provider_service.slices.all()[0]

                flavor = slice.default_flavor
                if not flavor:
                    flavors = Flavor.objects.filter(name="m1.small")
                    if not flavors:
                        raise XOSConfigurationError("No m1.small flavor")
                    flavor = flavors[0]

                if slice.default_isolation == "container_vm":
                    (node, parent) = ContainerVmScheduler(slice).pick()
                else:
                    (node, parent) = LeastLoadedNodeScheduler(slice).pick()

                instance = Instance(slice=slice,
                                    node=node,
                                    image=self.image,
                                    creator=self.creator,
                                    deployment=node.site_deployment.deployment,
                                    flavor=flavor,
                                    isolation=slice.default_isolation,
                                    parent=parent)
                self.save_instance(instance)
                new_instance_created = True

            try:
                self.instance = instance
                super(TenantWithContainer, self).save()
            except:
                if new_instance_created:
                    instance.delete()
                raise

    def cleanup_container(self):
        if self.instance:
            if self.get_attribute("use_same_instance_for_multiple_tenants", default=False):
                # Delete the instance only if this is last tenant in that
                # instance
                tenant_count = self.count_of_tenants_of_an_instance(
                    self.instance)
                if tenant_count == 0:
                    self.instance.delete()
            else:
                self.instance.delete()
            self.instance = None

    def save(self, *args, **kwargs):
        if (not self.creator) and (hasattr(self, "caller")) and (self.caller):
            self.creator = self.caller
        super(TenantWithContainer, self).save(*args, **kwargs)


class CoarseTenant(Tenant):
    """ TODO: rename "CoarseTenant" --> "StaticTenant" """
    class Meta:
        proxy = True

    KIND = COARSE_KIND

    def save(self, *args, **kwargs):
        if (not self.subscriber_service):
            raise XOSValidationError("subscriber_service cannot be null")
        if (self.subscriber_tenant or self.subscriber_user):
            raise XOSValidationError(
                "subscriber_tenant and subscriber_user must be null")

        super(CoarseTenant, self).save()


class Subscriber(TenantRoot):
    """ Intermediate class for TenantRoots that are to be Subscribers """

    class Meta:
        proxy = True

    KIND = "Subscriber"


class Provider(TenantRoot):
    """ Intermediate class for TenantRoots that are to be Providers """

    class Meta:
        proxy = True

    KIND = "Provider"


class TenantAttribute(PlCoreBase):
    name = models.CharField(help_text="Attribute Name", max_length=128)
    value = models.TextField(help_text="Attribute Value")
    tenant = models.ForeignKey(Tenant, related_name='tenantattributes',
                               help_text="The Tenant this attribute is associated with")

    def __unicode__(self): return u'%s-%s' % (self.name, self.id)


class TenantRootRole(PlCoreBase):
    ROLE_CHOICES = (('admin', 'Admin'), ('access', 'Access'))

    role = StrippedCharField(choices=ROLE_CHOICES, unique=True, max_length=30)

    def __unicode__(self): return u'%s' % (self.role)


class TenantRootPrivilege(PlCoreBase):
    user = models.ForeignKey('User', related_name="tenant_root_privileges")
    tenant_root = models.ForeignKey(
        'TenantRoot', related_name="tenant_root_privileges")
    role = models.ForeignKey(
        'TenantRootRole', related_name="tenant_root_privileges")

    class Meta:
        unique_together = ('user', 'tenant_root', 'role')

    def __unicode__(self): return u'%s %s %s' % (
        self.tenant_root, self.user, self.role)

    def save(self, *args, **kwds):
        if not self.user.is_active:
            raise PermissionDenied, "Cannot modify role(s) of a disabled user"
        super(TenantRootPrivilege, self).save(*args, **kwds)

    def can_update(self, user):
        return user.can_update_tenant_root_privilege(self)

    @classmethod
    def select_by_user(cls, user):
        if user.is_admin:
            return cls.objects.all()
        else:
            # User can see his own privilege
            trp_ids = [trp.id for trp in cls.objects.filter(user=user)]

            # A slice admin can see the SlicePrivileges for his Slice
            for priv in cls.objects.filter(user=user, role__role="admin"):
                trp_ids.extend(
                    [trp.id for trp in cls.objects.filter(tenant_root=priv.tenant_root)])

            return cls.objects.filter(id__in=trp_ids)


class TenantRole(PlCoreBase):
    """A TenantRole option."""
    ROLE_CHOICES = (('admin', 'Admin'), ('access', 'Access'))
    role = StrippedCharField(choices=ROLE_CHOICES, unique=True, max_length=30)

    def __unicode__(self): return u'%s' % (self.role)


class TenantPrivilege(PlCoreBase):
    """"A TenantPrivilege which defines how users can access a particular Tenant.

    Attributes:
        id (models.AutoField): The ID of the privilege.
        user (models.ForeignKey): A Foreign Key to the a User.
        tenant (models.ForeignKey): A ForeignKey to the Tenant.
        role (models.ForeignKey): A ForeignKey to the TenantRole.
    """
    id = models.AutoField(primary_key=True)
    user = models.ForeignKey('User', related_name="tenantprivileges")
    tenant = models.ForeignKey('Tenant', related_name="tenantprivileges")
    role = models.ForeignKey('TenantRole', related_name="tenantprivileges")

    def __unicode__(self): return u'%s %s %s' % (
        self.tenant, self.user, self.role)

    def save(self, *args, **kwds):
        if not self.user.is_active:
            raise PermissionDenied, "Cannot modify role(s) of a disabled user"
        super(TenantPrivilege, self).save(*args, **kwds)

    def can_update(self, user):
        return user.can_update_tenant_privilege(self)

    @classmethod
    def select_by_user(cls, user):
        if user.is_admin:
            return cls.objects.all()
        else:
            # User can see his own privilege
            trp_ids = [trp.id for trp in cls.objects.filter(user=user)]

            # A tenant admin can see the TenantPrivileges for their Tenants
            for priv in cls.objects.filter(user=user, role__role="admin"):
                trp_ids.extend(
                    [trp.id for trp in cls.objects.filter(tenant=priv.tenant)])

            return cls.objects.filter(id__in=trp_ids)