Merge "Cells: Add filtering and weight support"

13 files changed, 846 insertions, 31 deletions

diff --git a/etc/nova/policy.json b/etc/nova/policy.json
index d6524b6a2..b09f5f473 100644
--- a/etc/nova/policy.json
+++ b/etc/nova/policy.json
@@ -3,6 +3,7 @@
     "admin_or_owner":  "is_admin:True or project_id:%(project_id)s",
     "default": "rule:admin_or_owner",
 
+    "cells_scheduler_filter:TargetCellFilter": "is_admin:True",
 
     "compute:create": "",
     "compute:create:attach_network": "",
diff --git a/nova/cells/filters/__init__.py b/nova/cells/filters/__init__.py
new file mode 100644
index 000000000..f9b6d7a15
--- /dev/null
+++ b/nova/cells/filters/__init__.py
@@ -0,0 +1,62 @@
+# Copyright (c) 2012-2013 Rackspace Hosting
+# 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.
+
+"""
+Cell scheduler filters
+"""
+
+from nova import filters
+from nova.openstack.common import log as logging
+from nova import policy
+
+LOG = logging.getLogger(__name__)
+
+
+class BaseCellFilter(filters.BaseFilter):
+    """Base class for cell filters."""
+
+    def authorized(self, ctxt):
+        """Return whether or not the context is authorized for this filter
+        based on policy.
+        The policy action is "cells_scheduler_filter:<name>" where <name>
+        is the name of the filter class.
+        """
+        name = 'cells_scheduler_filter:' + self.__class__.__name__
+        target = {'project_id': ctxt.project_id,
+                  'user_id': ctxt.user_id}
+        return policy.enforce(ctxt, name, target, do_raise=False)
+
+    def _filter_one(self, cell, filter_properties):
+        return self.cell_passes(cell, filter_properties)
+
+    def cell_passes(self, cell, filter_properties):
+        """Return True if the CellState passes the filter, otherwise False.
+        Override this in a subclass.
+        """
+        raise NotImplementedError()
+
+
+class CellFilterHandler(filters.BaseFilterHandler):
+    def __init__(self):
+        super(CellFilterHandler, self).__init__(BaseCellFilter)
+
+
+def all_filters():
+    """Return a list of filter classes found in this directory.
+
+    This method is used as the default for available scheduler filters
+    and should return a list of all filter classes available.
+    """
+    return CellFilterHandler().get_all_classes()
diff --git a/nova/cells/filters/target_cell.py b/nova/cells/filters/target_cell.py
new file mode 100644
index 000000000..ab5adb1e8
--- /dev/null
+++ b/nova/cells/filters/target_cell.py
@@ -0,0 +1,68 @@
+# Copyright (c) 2012-2013 Rackspace Hosting
+# 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.
+
+"""
+Target cell filter.
+
+A scheduler hint of 'target_cell' with a value of a full cell name may be
+specified to route a build to a particular cell.  No error handling is
+done as there's no way to know whether the full path is a valid.
+"""
+
+from nova.cells import filters
+from nova.openstack.common import log as logging
+
+LOG = logging.getLogger(__name__)
+
+
+class TargetCellFilter(filters.BaseCellFilter):
+    """Target cell filter.  Works by specifying a scheduler hint of
+    'target_cell'. The value should be the full cell path.
+    """
+
+    def filter_all(self, cells, filter_properties):
+        """Override filter_all() which operates on the full list
+        of cells...
+        """
+        scheduler_hints = filter_properties.get('scheduler_hints')
+        if not scheduler_hints:
+            return cells
+
+        # This filter only makes sense at the top level, as a full
+        # cell name is specified.  So we pop 'target_cell' out of the
+        # hints dict.
+        cell_name = scheduler_hints.pop('target_cell', None)
+        if not cell_name:
+            return cells
+
+        # This authorization is after popping off target_cell, so
+        # that in case this fails, 'target_cell' is not left in the
+        # dict when child cells go to schedule.
+        if not self.authorized(filter_properties['context']):
+            # No filtering, if not authorized.
+            return cells
+
+        LOG.info(_("Forcing direct route to %(cell_name)s because "
+                   "of 'target_cell' scheduler hint"),
+                 {'cell_name': cell_name})
+
+        scheduler = filter_properties['scheduler']
+        if cell_name == filter_properties['routing_path']:
+            return [scheduler.state_manager.get_my_state()]
+        ctxt = filter_properties['context']
+        scheduler.msg_runner.schedule_run_instance(ctxt, cell_name,
+            filter_properties['host_sched_kwargs'])
+        # Returning None means to skip further scheduling, because we
+        # handled it.
diff --git a/nova/cells/scheduler.py b/nova/cells/scheduler.py
index 18389dbc5..c95498fa0 100644
--- a/nova/cells/scheduler.py
+++ b/nova/cells/scheduler.py
@@ -16,11 +16,13 @@
 """
 Cells Scheduler
 """
-import random
+import copy
 import time
 
 from oslo.config import cfg
 
+from nova.cells import filters
+from nova.cells import weights
 from nova import compute
 from nova.compute import instance_actions
 from nova.compute import utils as compute_utils
@@ -31,6 +33,16 @@ from nova.openstack.common import log as logging
 from nova.scheduler import rpcapi as scheduler_rpcapi
 
 cell_scheduler_opts = [
+        cfg.ListOpt('scheduler_filter_classes',
+                default=['nova.cells.filters.all_filters'],
+                help='Filter classes the cells scheduler should use.  '
+                        'An entry of "nova.cells.filters.all_filters"'
+                        'maps to all cells filters included with nova.'),
+        cfg.ListOpt('scheduler_weight_classes',
+                default=['nova.cells.weights.all_weighers'],
+                help='Weigher classes the cells scheduler should use.  '
+                        'An entry of "nova.cells.weights.all_weighers"'
+                        'maps to all cell weighers included with nova.'),
         cfg.IntOpt('scheduler_retries',
                 default=10,
                 help='How many retries when no cells are available.'),
@@ -55,6 +67,12 @@ class CellsScheduler(base.Base):
         self.state_manager = msg_runner.state_manager
         self.compute_api = compute.API()
         self.scheduler_rpcapi = scheduler_rpcapi.SchedulerAPI()
+        self.filter_handler = filters.CellFilterHandler()
+        self.filter_classes = self.filter_handler.get_matching_classes(
+                CONF.cells.scheduler_filter_classes)
+        self.weight_handler = weights.CellWeightHandler()
+        self.weigher_classes = self.weight_handler.get_matching_classes(
+                CONF.cells.scheduler_weight_classes)
 
     def _create_instances_here(self, ctxt, request_spec):
         instance_values = request_spec['instance_properties']
@@ -79,11 +97,11 @@ class CellsScheduler(base.Base):
             self.db.action_start(ctxt, action)
 
     def _get_possible_cells(self):
-        cells = set(self.state_manager.get_child_cells())
+        cells = self.state_manager.get_child_cells()
         our_cell = self.state_manager.get_my_state()
         # Include our cell in the list, if we have any capacity info
         if not cells or our_cell.capacities:
-            cells.add(our_cell)
+            cells.append(our_cell)
         return cells
 
     def _run_instance(self, message, host_sched_kwargs):
@@ -91,33 +109,66 @@ class CellsScheduler(base.Base):
         to try, raise exception.NoCellsAvailable
         """
         ctxt = message.ctxt
+        routing_path = message.routing_path
         request_spec = host_sched_kwargs['request_spec']
 
-        # The message we might forward to a child cell
+        LOG.debug(_("Scheduling with routing_path=%(routing_path)s"),
+                  {'routing_path': routing_path})
+
+        filter_properties = copy.copy(host_sched_kwargs['filter_properties'])
+        filter_properties.update({'context': ctxt,
+                                  'scheduler': self,
+                                  'routing_path': routing_path,
+                                  'host_sched_kwargs': host_sched_kwargs,
+                                  'request_spec': request_spec})
+
         cells = self._get_possible_cells()
+        cells = self.filter_handler.get_filtered_objects(self.filter_classes,
+                                                         cells,
+                                                         filter_properties)
+        # NOTE(comstud): I know this reads weird, but the 'if's are nested
+        # this way to optimize for the common case where 'cells' is a list
+        # containing at least 1 entry.
         if not cells:
+            if cells is None:
+                # None means to bypass further scheduling as a filter
+                # took care of everything.
+                return
             raise exception.NoCellsAvailable()
-        cells = list(cells)
 
-        # Random selection for now
-        random.shuffle(cells)
-        target_cell = cells[0]
-
-        LOG.debug(_("Scheduling with routing_path=%(routing_path)s"),
-                  {'routing_path': message.routing_path})
-
-        if target_cell.is_me:
-            # Need to create instance DB entries as the host scheduler
-            # expects that the instance(s) already exists.
-            self._create_instances_here(ctxt, request_spec)
-            # Need to record the create action in the db as the scheduler
-            # expects it to already exist.
-            self._create_action_here(ctxt, request_spec['instance_uuids'])
-            self.scheduler_rpcapi.run_instance(ctxt,
-                    **host_sched_kwargs)
-            return
-        self.msg_runner.schedule_run_instance(ctxt, target_cell,
-                                              host_sched_kwargs)
+        weighted_cells = self.weight_handler.get_weighed_objects(
+                self.weigher_classes, cells, filter_properties)
+        LOG.debug(_("Weighted cells: %(weighted_cells)s"),
+                  {'weighted_cells': weighted_cells})
+
+        # Keep trying until one works
+        for weighted_cell in weighted_cells:
+            cell = weighted_cell.obj
+            try:
+                if cell.is_me:
+                    # Need to create instance DB entry as scheduler
+                    # thinks it's already created... At least how things
+                    # currently work.
+                    self._create_instances_here(ctxt, request_spec)
+                    # Need to record the create action in the db as the
+                    # scheduler expects it to already exist.
+                    self._create_action_here(
+                            ctxt, request_spec['instance_uuids'])
+                    self.scheduler_rpcapi.run_instance(ctxt,
+                            **host_sched_kwargs)
+                    return
+                # Forward request to cell
+                self.msg_runner.schedule_run_instance(ctxt, cell,
+                                                      host_sched_kwargs)
+                return
+            except Exception:
+                LOG.exception(_("Couldn't communicate with cell '%s'") %
+                        cell.name)
+        # FIXME(comstud): Would be nice to kick this back up so that
+        # the parent cell could retry, if we had a parent.
+        msg = _("Couldn't communicate with any cells")
+        LOG.error(msg)
+        raise exception.NoCellsAvailable()
 
     def run_instance(self, message, host_sched_kwargs):
         """Pick a cell where we should create a new instance."""
diff --git a/nova/cells/weights/__init__.py b/nova/cells/weights/__init__.py
new file mode 100644
index 000000000..202a6a31a
--- /dev/null
+++ b/nova/cells/weights/__init__.py
@@ -0,0 +1,43 @@
+# Copyright (c) 2012-2013 Rackspace Hosting
+# 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.
+
+"""
+Cell Scheduler weights
+"""
+
+from nova import weights
+
+
+class WeightedCell(weights.WeighedObject):
+    def __repr__(self):
+        return "WeightedCell [cell: %s, weight: %s]" % (
+                self.obj.name, self.weight)
+
+
+class BaseCellWeigher(weights.BaseWeigher):
+    """Base class for cell weights."""
+    pass
+
+
+class CellWeightHandler(weights.BaseWeightHandler):
+    object_class = WeightedCell
+
+    def __init__(self):
+        super(CellWeightHandler, self).__init__(BaseCellWeigher)
+
+
+def all_weighers():
+    """Return a list of weight plugin classes found in this directory."""
+    return CellWeightHandler().get_all_classes()
diff --git a/nova/cells/weights/ram_by_instance_type.py b/nova/cells/weights/ram_by_instance_type.py
new file mode 100644
index 000000000..1a1d164d2
--- /dev/null
+++ b/nova/cells/weights/ram_by_instance_type.py
@@ -0,0 +1,54 @@
+# Copyright (c) 2012-2013 Rackspace Hosting
+# 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.
+
+"""
+Weigh cells by memory needed in a way that spreads instances.
+"""
+from oslo.config import cfg
+
+from nova.cells import weights
+
+ram_weigher_opts = [
+        cfg.FloatOpt('ram_weight_multiplier',
+                     default=10.0,
+                     help='Multiplier used for weighing ram.  Negative '
+                          'numbers mean to stack vs spread.'),
+]
+
+CONF = cfg.CONF
+CONF.register_opts(ram_weigher_opts, group='cells')
+
+
+class RamByInstanceTypeWeigher(weights.BaseCellWeigher):
+    """Weigh cells by instance_type requested."""
+
+    def _weight_multiplier(self):
+        return CONF.cells.ram_weight_multiplier
+
+    def _weigh_object(self, cell, weight_properties):
+        """
+        Use the 'ram_free' for a particular instance_type advertised from a
+        child cell's capacity to compute a weight.  We want to direct the
+        build to a cell with a higher capacity.  Since higher weights win,
+        we just return the number of units available for the instance_type.
+        """
+        request_spec = weight_properties['request_spec']
+        instance_type = request_spec['instance_type']
+        memory_needed = instance_type['memory_mb']
+
+        ram_free = cell.capacities.get('ram_free', {})
+        units_by_mb = ram_free.get('units_by_mb', {})
+
+        return units_by_mb.get(str(memory_needed), 0)
diff --git a/nova/cells/weights/weight_offset.py b/nova/cells/weights/weight_offset.py
new file mode 100644
index 000000000..14348ee20
--- /dev/null
+++ b/nova/cells/weights/weight_offset.py
@@ -0,0 +1,33 @@
+# Copyright (c) 2012-2013 Rackspace Hosting
+# 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.
+
+"""
+Weigh cells by their weight_offset in the DB.  Cells with higher
+weight_offsets in the DB will be preferred.
+"""
+
+from nova.cells import weights
+
+
+class WeightOffsetWeigher(weights.BaseCellWeigher):
+    """
+    Weight cell by weight_offset db field.
+    Originally designed so you can set a default cell by putting
+    its weight_offset to 999999999999999 (highest weight wins)
+    """
+
+    def _weigh_object(self, cell, weight_properties):
+        """Returns whatever was in the DB for weight_offset."""
+        return cell.db_info.get('weight_offset', 0)
diff --git a/nova/filters.py b/nova/filters.py
index 18e3a7d66..4b7f9ff10 100644
--- a/nova/filters.py
+++ b/nova/filters.py
@@ -54,8 +54,14 @@ class BaseFilterHandler(loadables.BaseLoader):
         list_objs = list(objs)
         LOG.debug("Starting with %d host(s)", len(list_objs))
         for filter_cls in filter_classes:
-            list_objs = list(filter_cls().filter_all(list_objs,
-                             filter_properties))
-            LOG.debug("Filter %s returned %d host(s)",
-                      filter_cls.__name__, len(list_objs))
+            cls_name = filter_cls.__name__
+            objs = filter_cls().filter_all(list_objs,
+                                           filter_properties)
+            if objs is None:
+                LOG.debug("Filter %(cls_name)s says to stop filtering",
+                          {'cls_name': cls_name})
+                return
+            list_objs = list(objs)
+            LOG.debug("Filter %(cls_name)s returned %(obj_len)d host(s)",
+                      {'cls_name': cls_name, 'obj_len': len(list_objs)})
         return list_objs
diff --git a/nova/tests/cells/test_cells_filters.py b/nova/tests/cells/test_cells_filters.py
new file mode 100644
index 000000000..e11e6c640
--- /dev/null
+++ b/nova/tests/cells/test_cells_filters.py
@@ -0,0 +1,121 @@
+# Copyright (c) 2012-2013 Rackspace Hosting
+# 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.
+"""
+Unit Tests for cells scheduler filters.
+"""
+
+from nova.cells import filters
+from nova import context
+from nova import test
+from nova.tests.cells import fakes
+
+
+class FiltersTestCase(test.TestCase):
+    """Makes sure the proper filters are in the directory."""
+
+    def test_all_filters(self):
+        filter_classes = filters.all_filters()
+        class_names = [cls.__name__ for cls in filter_classes]
+        self.assertIn("TargetCellFilter", class_names)
+
+
+class _FilterTestClass(test.TestCase):
+    """Base class for testing individual filter plugins."""
+    filter_cls_name = None
+
+    def setUp(self):
+        super(_FilterTestClass, self).setUp()
+        fakes.init(self)
+        self.msg_runner = fakes.get_message_runner('api-cell')
+        self.scheduler = self.msg_runner.scheduler
+        self.my_cell_state = self.msg_runner.state_manager.get_my_state()
+        self.filter_handler = filters.CellFilterHandler()
+        self.filter_classes = self.filter_handler.get_matching_classes(
+                [self.filter_cls_name])
+        self.context = context.RequestContext('fake', 'fake',
+                                              is_admin=True)
+
+    def _filter_cells(self, cells, filter_properties):
+        return self.filter_handler.get_filtered_objects(self.filter_classes,
+                                                        cells,
+                                                        filter_properties)
+
+
+class TestTargetCellFilter(_FilterTestClass):
+    filter_cls_name = 'nova.cells.filters.target_cell.TargetCellFilter'
+
+    def test_missing_scheduler_hints(self):
+        cells = [1, 2, 3]
+        # No filtering
+        filter_props = {'context': self.context}
+        self.assertEqual(cells, self._filter_cells(cells, filter_props))
+
+    def test_no_target_cell_hint(self):
+        cells = [1, 2, 3]
+        filter_props = {'scheduler_hints': {},
+                        'context': self.context}
+        # No filtering
+        self.assertEqual(cells, self._filter_cells(cells, filter_props))
+
+    def test_target_cell_specified_me(self):
+        cells = [1, 2, 3]
+        target_cell = 'fake!cell!path'
+        current_cell = 'fake!cell!path'
+        filter_props = {'scheduler_hints': {'target_cell': target_cell},
+                        'routing_path': current_cell,
+                        'scheduler': self.scheduler,
+                        'context': self.context}
+        # Only myself in the list.
+        self.assertEqual([self.my_cell_state],
+                         self._filter_cells(cells, filter_props))
+
+    def test_target_cell_specified_me_but_not_admin(self):
+        ctxt = context.RequestContext('fake', 'fake')
+        cells = [1, 2, 3]
+        target_cell = 'fake!cell!path'
+        current_cell = 'fake!cell!path'
+        filter_props = {'scheduler_hints': {'target_cell': target_cell},
+                        'routing_path': current_cell,
+                        'scheduler': self.scheduler,
+                        'context': ctxt}
+        # No filtering, because not an admin.
+        self.assertEqual(cells, self._filter_cells(cells, filter_props))
+
+    def test_target_cell_specified_not_me(self):
+        info = {}
+
+        def _fake_sched_run_instance(ctxt, cell, sched_kwargs):
+            info['ctxt'] = ctxt
+            info['cell'] = cell
+            info['sched_kwargs'] = sched_kwargs
+
+        self.stubs.Set(self.msg_runner, 'schedule_run_instance',
+                       _fake_sched_run_instance)
+        cells = [1, 2, 3]
+        target_cell = 'fake!cell!path'
+        current_cell = 'not!the!same'
+        filter_props = {'scheduler_hints': {'target_cell': target_cell},
+                        'routing_path': current_cell,
+                        'scheduler': self.scheduler,
+                        'context': self.context,
+                        'host_sched_kwargs': 'meow'}
+        # None is returned to bypass further scheduling.
+        self.assertEqual(None,
+                         self._filter_cells(cells, filter_props))
+        # The filter should have re-scheduled to the child cell itself.
+        expected_info = {'ctxt': self.context,
+                         'cell': 'fake!cell!path',
+                         'sched_kwargs': 'meow'}
+        self.assertEqual(expected_info, info)
diff --git a/nova/tests/cells/test_cells_scheduler.py b/nova/tests/cells/test_cells_scheduler.py
index c9e626385..c8f90619e 100644
--- a/nova/tests/cells/test_cells_scheduler.py
+++ b/nova/tests/cells/test_cells_scheduler.py
@@ -19,6 +19,8 @@ import time
 
 from oslo.config import cfg
 
+from nova.cells import filters
+from nova.cells import weights
 from nova.compute import vm_states
 from nova import context
 from nova import db
@@ -29,6 +31,26 @@ from nova.tests.cells import fakes
 
 CONF = cfg.CONF
 CONF.import_opt('scheduler_retries', 'nova.cells.scheduler', group='cells')
+CONF.import_opt('scheduler_filter_classes', 'nova.cells.scheduler',
+                group='cells')
+CONF.import_opt('scheduler_weight_classes', 'nova.cells.scheduler',
+                group='cells')
+
+
+class FakeFilterClass1(filters.BaseCellFilter):
+    pass
+
+
+class FakeFilterClass2(filters.BaseCellFilter):
+    pass
+
+
+class FakeWeightClass1(weights.BaseCellWeigher):
+    pass
+
+
+class FakeWeightClass2(weights.BaseCellWeigher):
+    pass
 
 
 class CellsSchedulerTestCase(test.TestCase):
@@ -36,6 +58,11 @@ class CellsSchedulerTestCase(test.TestCase):
 
     def setUp(self):
         super(CellsSchedulerTestCase, self).setUp()
+        self.flags(scheduler_filter_classes=[], scheduler_weight_classes=[],
+                   group='cells')
+        self._init_cells_scheduler()
+
+    def _init_cells_scheduler(self):
         fakes.init(self)
         self.msg_runner = fakes.get_message_runner('api-cell')
         self.scheduler = self.msg_runner.scheduler
@@ -109,7 +136,8 @@ class CellsSchedulerTestCase(test.TestCase):
         self.stubs.Set(self.msg_runner, 'schedule_run_instance',
                 msg_runner_schedule_run_instance)
 
-        host_sched_kwargs = {'request_spec': self.request_spec}
+        host_sched_kwargs = {'request_spec': self.request_spec,
+                             'filter_properties': {}}
         self.msg_runner.schedule_run_instance(self.ctxt,
                 self.my_cell_state, host_sched_kwargs)
 
@@ -138,6 +166,7 @@ class CellsSchedulerTestCase(test.TestCase):
                        'run_instance', fake_rpc_run_instance)
 
         host_sched_kwargs = {'request_spec': self.request_spec,
+                             'filter_properties': {},
                              'other': 'stuff'}
         self.msg_runner.schedule_run_instance(self.ctxt,
                 self.my_cell_state, host_sched_kwargs)
@@ -149,7 +178,8 @@ class CellsSchedulerTestCase(test.TestCase):
     def test_run_instance_retries_when_no_cells_avail(self):
         self.flags(scheduler_retries=7, group='cells')
 
-        host_sched_kwargs = {'request_spec': self.request_spec}
+        host_sched_kwargs = {'request_spec': self.request_spec,
+                             'filter_properties': {}}
 
         call_info = {'num_tries': 0, 'errored_uuids': []}
 
@@ -177,7 +207,8 @@ class CellsSchedulerTestCase(test.TestCase):
     def test_run_instance_on_random_exception(self):
         self.flags(scheduler_retries=7, group='cells')
 
-        host_sched_kwargs = {'request_spec': self.request_spec}
+        host_sched_kwargs = {'request_spec': self.request_spec,
+                             'filter_properties': {}}
 
         call_info = {'num_tries': 0,
                      'errored_uuids1': [],
@@ -206,3 +237,148 @@ class CellsSchedulerTestCase(test.TestCase):
         self.assertEqual(1, call_info['num_tries'])
         self.assertEqual(self.instance_uuids, call_info['errored_uuids1'])
         self.assertEqual(self.instance_uuids, call_info['errored_uuids2'])
+
+    def test_cells_filter_args_correct(self):
+        # Re-init our fakes with some filters.
+        our_path = 'nova.tests.cells.test_cells_scheduler'
+        cls_names = [our_path + '.' + 'FakeFilterClass1',
+                     our_path + '.' + 'FakeFilterClass2']
+        self.flags(scheduler_filter_classes=cls_names, group='cells')
+        self._init_cells_scheduler()
+
+        # Make sure there's no child cells so that we will be
+        # selected.  Makes stubbing easier.
+        self.state_manager.child_cells = {}
+
+        call_info = {}
+
+        def fake_create_instances_here(ctxt, request_spec):
+            call_info['ctxt'] = ctxt
+            call_info['request_spec'] = request_spec
+
+        def fake_rpc_run_instance(ctxt, **host_sched_kwargs):
+            call_info['host_sched_kwargs'] = host_sched_kwargs
+
+        def fake_get_filtered_objs(filter_classes, cells, filt_properties):
+            call_info['filt_classes'] = filter_classes
+            call_info['filt_cells'] = cells
+            call_info['filt_props'] = filt_properties
+            return cells
+
+        self.stubs.Set(self.scheduler, '_create_instances_here',
+                fake_create_instances_here)
+        self.stubs.Set(self.scheduler.scheduler_rpcapi,
+                       'run_instance', fake_rpc_run_instance)
+        filter_handler = self.scheduler.filter_handler
+        self.stubs.Set(filter_handler, 'get_filtered_objects',
+                       fake_get_filtered_objs)
+
+        host_sched_kwargs = {'request_spec': self.request_spec,
+                             'filter_properties': {},
+                             'other': 'stuff'}
+
+        self.msg_runner.schedule_run_instance(self.ctxt,
+                self.my_cell_state, host_sched_kwargs)
+        # Our cell was selected.
+        self.assertEqual(self.ctxt, call_info['ctxt'])
+        self.assertEqual(self.request_spec, call_info['request_spec'])
+        self.assertEqual(host_sched_kwargs, call_info['host_sched_kwargs'])
+        # Filter args are correct
+        expected_filt_props = {'context': self.ctxt,
+                               'scheduler': self.scheduler,
+                               'routing_path': self.my_cell_state.name,
+                               'host_sched_kwargs': host_sched_kwargs,
+                               'request_spec': self.request_spec}
+        self.assertEqual(expected_filt_props, call_info['filt_props'])
+        self.assertEqual([FakeFilterClass1, FakeFilterClass2],
+                         call_info['filt_classes'])
+        self.assertEqual([self.my_cell_state], call_info['filt_cells'])
+
+    def test_cells_filter_returning_none(self):
+        # Re-init our fakes with some filters.
+        our_path = 'nova.tests.cells.test_cells_scheduler'
+        cls_names = [our_path + '.' + 'FakeFilterClass1',
+                     our_path + '.' + 'FakeFilterClass2']
+        self.flags(scheduler_filter_classes=cls_names, group='cells')
+        self._init_cells_scheduler()
+
+        # Make sure there's no child cells so that we will be
+        # selected.  Makes stubbing easier.
+        self.state_manager.child_cells = {}
+
+        call_info = {'scheduled': False}
+
+        def fake_create_instances_here(ctxt, request_spec):
+            # Should not be called
+            call_info['scheduled'] = True
+
+        def fake_get_filtered_objs(filter_classes, cells, filt_properties):
+            # Should cause scheduling to be skipped.  Means that the
+            # filter did it.
+            return None
+
+        self.stubs.Set(self.scheduler, '_create_instances_here',
+                fake_create_instances_here)
+        filter_handler = self.scheduler.filter_handler
+        self.stubs.Set(filter_handler, 'get_filtered_objects',
+                       fake_get_filtered_objs)
+
+        self.msg_runner.schedule_run_instance(self.ctxt,
+                self.my_cell_state, {})
+        self.assertFalse(call_info['scheduled'])
+
+    def test_cells_weight_args_correct(self):
+        # Re-init our fakes with some filters.
+        our_path = 'nova.tests.cells.test_cells_scheduler'
+        cls_names = [our_path + '.' + 'FakeWeightClass1',
+                     our_path + '.' + 'FakeWeightClass2']
+        self.flags(scheduler_weight_classes=cls_names, group='cells')
+        self._init_cells_scheduler()
+
+        # Make sure there's no child cells so that we will be
+        # selected.  Makes stubbing easier.
+        self.state_manager.child_cells = {}
+
+        call_info = {}
+
+        def fake_create_instances_here(ctxt, request_spec):
+            call_info['ctxt'] = ctxt
+            call_info['request_spec'] = request_spec
+
+        def fake_rpc_run_instance(ctxt, **host_sched_kwargs):
+            call_info['host_sched_kwargs'] = host_sched_kwargs
+
+        def fake_get_weighed_objs(weight_classes, cells, filt_properties):
+            call_info['weight_classes'] = weight_classes
+            call_info['weight_cells'] = cells
+            call_info['weight_props'] = filt_properties
+            return [weights.WeightedCell(cells[0], 0.0)]
+
+        self.stubs.Set(self.scheduler, '_create_instances_here',
+                fake_create_instances_here)
+        self.stubs.Set(self.scheduler.scheduler_rpcapi,
+                       'run_instance', fake_rpc_run_instance)
+        weight_handler = self.scheduler.weight_handler
+        self.stubs.Set(weight_handler, 'get_weighed_objects',
+                       fake_get_weighed_objs)
+
+        host_sched_kwargs = {'request_spec': self.request_spec,
+                             'filter_properties': {},
+                             'other': 'stuff'}
+
+        self.msg_runner.schedule_run_instance(self.ctxt,
+                self.my_cell_state, host_sched_kwargs)
+        # Our cell was selected.
+        self.assertEqual(self.ctxt, call_info['ctxt'])
+        self.assertEqual(self.request_spec, call_info['request_spec'])
+        self.assertEqual(host_sched_kwargs, call_info['host_sched_kwargs'])
+        # Weight args are correct
+        expected_filt_props = {'context': self.ctxt,
+                               'scheduler': self.scheduler,
+                               'routing_path': self.my_cell_state.name,
+                               'host_sched_kwargs': host_sched_kwargs,
+                               'request_spec': self.request_spec}
+        self.assertEqual(expected_filt_props, call_info['weight_props'])
+        self.assertEqual([FakeWeightClass1, FakeWeightClass2],
+                         call_info['weight_classes'])
+        self.assertEqual([self.my_cell_state], call_info['weight_cells'])
diff --git a/nova/tests/cells/test_cells_weights.py b/nova/tests/cells/test_cells_weights.py
new file mode 100644
index 000000000..ca01e9939
--- /dev/null
+++ b/nova/tests/cells/test_cells_weights.py
@@ -0,0 +1,165 @@
+# Copyright (c) 2012 Openstack, LLC
+# 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.
+"""
+Unit Tests for testing the cells weight algorithms.
+
+Cells with higher weights should be given priority for new builds.
+"""
+
+from nova.cells import state
+from nova.cells import weights
+from nova import test
+
+
+class FakeCellState(state.CellState):
+    def __init__(self, cell_name):
+        super(FakeCellState, self).__init__(cell_name)
+        self.capacities['ram_free'] = {'total_mb': 0,
+                                       'units_by_mb': {}}
+        self.db_info = {}
+
+    def _update_ram_free(self, *args):
+        ram_free = self.capacities['ram_free']
+        for ram_size, units in args:
+            ram_free['total_mb'] += units * ram_size
+            ram_free['units_by_mb'][str(ram_size)] = units
+
+
+def _get_fake_cells():
+
+    cell1 = FakeCellState('cell1')
+    cell1._update_ram_free((512, 1), (1024, 4), (2048, 3))
+    cell1.db_info['weight_offset'] = -200.0
+    cell2 = FakeCellState('cell2')
+    cell2._update_ram_free((512, 2), (1024, 3), (2048, 4))
+    cell2.db_info['weight_offset'] = -200.1
+    cell3 = FakeCellState('cell3')
+    cell3._update_ram_free((512, 3), (1024, 2), (2048, 1))
+    cell3.db_info['weight_offset'] = 400.0
+    cell4 = FakeCellState('cell4')
+    cell4._update_ram_free((512, 4), (1024, 1), (2048, 2))
+    cell4.db_info['weight_offset'] = 300.0
+
+    return [cell1, cell2, cell3, cell4]
+
+
+class CellsWeightsTestCase(test.TestCase):
+    """Makes sure the proper weighers are in the directory."""
+
+    def test_all_weighers(self):
+        weighers = weights.all_weighers()
+        # Check at least a couple that we expect are there
+        self.assertTrue(len(weighers) >= 2)
+        class_names = [cls.__name__ for cls in weighers]
+        self.assertIn('WeightOffsetWeigher', class_names)
+        self.assert_('RamByInstanceTypeWeigher', class_names)
+
+
+class _WeigherTestClass(test.TestCase):
+    """Base class for testing individual weigher plugins."""
+    weigher_cls_name = None
+
+    def setUp(self):
+        super(_WeigherTestClass, self).setUp()
+        self.weight_handler = weights.CellWeightHandler()
+        self.weight_classes = self.weight_handler.get_matching_classes(
+                [self.weigher_cls_name])
+
+    def _get_weighed_cells(self, cells, weight_properties):
+        return self.weight_handler.get_weighed_objects(self.weight_classes,
+                cells, weight_properties)
+
+
+class RAMByInstanceTypeWeigherTestClass(_WeigherTestClass):
+
+    weigher_cls_name = ('nova.cells.weights.ram_by_instance_type.'
+                        'RamByInstanceTypeWeigher')
+
+    def test_default_spreading(self):
+        """Test that cells with more ram available return a higher weight."""
+        cells = _get_fake_cells()
+        # Simulate building a new 512MB instance.
+        instance_type = {'memory_mb': 512}
+        weight_properties = {'request_spec': {'instance_type': instance_type}}
+        weighed_cells = self._get_weighed_cells(cells, weight_properties)
+        self.assertEqual(len(weighed_cells), 4)
+        resulting_cells = [weighed_cell.obj for weighed_cell in weighed_cells]
+        expected_cells = [cells[3], cells[2], cells[1], cells[0]]
+        self.assertEqual(expected_cells, resulting_cells)
+
+        # Simulate building a new 1024MB instance.
+        instance_type = {'memory_mb': 1024}
+        weight_properties = {'request_spec': {'instance_type': instance_type}}
+        weighed_cells = self._get_weighed_cells(cells, weight_properties)
+        self.assertEqual(len(weighed_cells), 4)
+        resulting_cells = [weighed_cell.obj for weighed_cell in weighed_cells]
+        expected_cells = [cells[0], cells[1], cells[2], cells[3]]
+        self.assertEqual(expected_cells, resulting_cells)
+
+        # Simulate building a new 2048MB instance.
+        instance_type = {'memory_mb': 2048}
+        weight_properties = {'request_spec': {'instance_type': instance_type}}
+        weighed_cells = self._get_weighed_cells(cells, weight_properties)
+        self.assertEqual(len(weighed_cells), 4)
+        resulting_cells = [weighed_cell.obj for weighed_cell in weighed_cells]
+        expected_cells = [cells[1], cells[0], cells[3], cells[2]]
+        self.assertEqual(expected_cells, resulting_cells)
+
+    def test_negative_multiplier(self):
+        """Test that cells with less ram available return a higher weight."""
+        self.flags(ram_weight_multiplier=-1.0, group='cells')
+        cells = _get_fake_cells()
+        # Simulate building a new 512MB instance.
+        instance_type = {'memory_mb': 512}
+        weight_properties = {'request_spec': {'instance_type': instance_type}}
+        weighed_cells = self._get_weighed_cells(cells, weight_properties)
+        self.assertEqual(len(weighed_cells), 4)
+        resulting_cells = [weighed_cell.obj for weighed_cell in weighed_cells]
+        expected_cells = [cells[0], cells[1], cells[2], cells[3]]
+        self.assertEqual(expected_cells, resulting_cells)
+
+        # Simulate building a new 1024MB instance.
+        instance_type = {'memory_mb': 1024}
+        weight_properties = {'request_spec': {'instance_type': instance_type}}
+        weighed_cells = self._get_weighed_cells(cells, weight_properties)
+        self.assertEqual(len(weighed_cells), 4)
+        resulting_cells = [weighed_cell.obj for weighed_cell in weighed_cells]
+        expected_cells = [cells[3], cells[2], cells[1], cells[0]]
+        self.assertEqual(expected_cells, resulting_cells)
+
+        # Simulate building a new 2048MB instance.
+        instance_type = {'memory_mb': 2048}
+        weight_properties = {'request_spec': {'instance_type': instance_type}}
+        weighed_cells = self._get_weighed_cells(cells, weight_properties)
+        self.assertEqual(len(weighed_cells), 4)
+        resulting_cells = [weighed_cell.obj for weighed_cell in weighed_cells]
+        expected_cells = [cells[2], cells[3], cells[0], cells[1]]
+        self.assertEqual(expected_cells, resulting_cells)
+
+
+class WeightOffsetWeigherTestClass(_WeigherTestClass):
+    """Test the RAMWeigher class."""
+    weigher_cls_name = 'nova.cells.weights.weight_offset.WeightOffsetWeigher'
+
+    def test_weight_offset(self):
+        """Test that cells with higher weight_offsets return higher
+        weights.
+        """
+        cells = _get_fake_cells()
+        weighed_cells = self._get_weighed_cells(cells, {})
+        self.assertEqual(len(weighed_cells), 4)
+        expected_cells = [cells[2], cells[3], cells[0], cells[1]]
+        resulting_cells = [weighed_cell.obj for weighed_cell in weighed_cells]
+        self.assertEqual(expected_cells, resulting_cells)
diff --git a/nova/tests/fake_policy.py b/nova/tests/fake_policy.py
index b30793ac4..b09944878 100644
--- a/nova/tests/fake_policy.py
+++ b/nova/tests/fake_policy.py
@@ -19,6 +19,8 @@ policy_data = """
 {
     "admin_api": "role:admin",
 
+    "cells_scheduler_filter:TargetCellFilter": "is_admin:True",
+
     "context_is_admin": "role:admin or role:administrator",
     "compute:create": "",
     "compute:create:attach_network": "",
diff --git a/nova/tests/test_filters.py b/nova/tests/test_filters.py
index 3940ce0c3..c06b50fde 100644
--- a/nova/tests/test_filters.py
+++ b/nova/tests/test_filters.py
@@ -123,3 +123,36 @@ class FiltersTestCase(test.TestCase):
                                                      filter_objs_initial,
                                                      filter_properties)
         self.assertEqual(filter_objs_last, result)
+
+    def test_get_filtered_objects_none_response(self):
+        filter_objs_initial = ['initial', 'filter1', 'objects1']
+        filter_properties = 'fake_filter_properties'
+
+        def _fake_base_loader_init(*args, **kwargs):
+            pass
+
+        self.stubs.Set(loadables.BaseLoader, '__init__',
+                       _fake_base_loader_init)
+
+        filt1_mock = self.mox.CreateMock(Filter1)
+        filt2_mock = self.mox.CreateMock(Filter2)
+
+        self.mox.StubOutWithMock(sys.modules[__name__], 'Filter1',
+                                 use_mock_anything=True)
+        self.mox.StubOutWithMock(filt1_mock, 'filter_all')
+        # Shouldn't be called.
+        self.mox.StubOutWithMock(sys.modules[__name__], 'Filter2',
+                                 use_mock_anything=True)
+        self.mox.StubOutWithMock(filt2_mock, 'filter_all')
+
+        Filter1().AndReturn(filt1_mock)
+        filt1_mock.filter_all(filter_objs_initial,
+                              filter_properties).AndReturn(None)
+        self.mox.ReplayAll()
+
+        filter_handler = filters.BaseFilterHandler(filters.BaseFilter)
+        filter_classes = [Filter1, Filter2]
+        result = filter_handler.get_filtered_objects(filter_classes,
+                                                     filter_objs_initial,
+                                                     filter_properties)
+        self.assertEqual(None, result)