Refactor scheduling filters

This changes the scheduling filters to use the code in nova/loadables.py
to locate filtering classes.  This also creates some base functionality
in nova/filters.py to be used by both the host scheduler and the cells
scheduler.

The scheduler_available_filters default has changed to
'nova.scheduler.filters.all_filters' which is better named compared to
the old setting of 'standard_filters'.  The old method is still
supported for those that have put it explicitly in their configs, but
it's marked as deprecated.

DocImpact

Change-Id: I84fdeafdba0275ab4b25f8857563bd7b1494bb69

nova/tests/test_filters.py

@@ -0,0 +1,125 @@
+# Copyright 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.
+"""
+Tests For Scheduler Host Filters.
+"""
+
+import inspect
+import sys
+
+from nova import filters
+from nova import loadables
+from nova import test
+
+
+class Filter1(filters.BaseFilter):
+    """Test Filter class #1."""
+    pass
+
+
+class Filter2(filters.BaseFilter):
+    """Test Filter class #2."""
+    pass
+
+
+class FiltersTestCase(test.TestCase):
+    def test_filter_all(self):
+        filter_obj_list = ['obj1', 'obj2', 'obj3']
+        filter_properties = 'fake_filter_properties'
+        base_filter = filters.BaseFilter()
+
+        self.mox.StubOutWithMock(base_filter, '_filter_one')
+
+        base_filter._filter_one('obj1', filter_properties).AndReturn(True)
+        base_filter._filter_one('obj2', filter_properties).AndReturn(False)
+        base_filter._filter_one('obj3', filter_properties).AndReturn(True)
+
+        self.mox.ReplayAll()
+
+        result = base_filter.filter_all(filter_obj_list, filter_properties)
+        self.assertTrue(inspect.isgenerator(result))
+        self.assertEqual(list(result), ['obj1', 'obj3'])
+
+    def test_filter_all_recursive_yields(self):
+        """Test filter_all() allows generators from previous filter_all()s."""
+        # filter_all() yields results.  We want to make sure that we can
+        # call filter_all() with generators returned from previous calls
+        # to filter_all().
+        filter_obj_list = ['obj1', 'obj2', 'obj3']
+        filter_properties = 'fake_filter_properties'
+        base_filter = filters.BaseFilter()
+
+        self.mox.StubOutWithMock(base_filter, '_filter_one')
+
+        total_iterations = 200
+
+        # The order that _filter_one is going to get called gets
+        # confusing because we will be recursively yielding things..
+        # We are going to simulate the first call to filter_all()
+        # returning False for 'obj2'.  So, 'obj1' will get yielded
+        # 'total_iterations' number of times before the first filter_all()
+        # call gets to processing 'obj2'.  We then return 'False' for it.
+        # After that, 'obj3' gets yielded 'total_iterations' number of
+        # times.
+        for x in xrange(total_iterations):
+            base_filter._filter_one('obj1', filter_properties).AndReturn(True)
+        base_filter._filter_one('obj2', filter_properties).AndReturn(False)
+        for x in xrange(total_iterations):
+            base_filter._filter_one('obj3', filter_properties).AndReturn(True)
+        self.mox.ReplayAll()
+
+        objs = iter(filter_obj_list)
+        for x in xrange(total_iterations):
+            # Pass in generators returned from previous calls.
+            objs = base_filter.filter_all(objs, filter_properties)
+        self.assertTrue(inspect.isgenerator(objs))
+        self.assertEqual(list(objs), ['obj1', 'obj3'])
+
+    def test_get_filtered_objects(self):
+        filter_objs_initial = ['initial', 'filter1', 'objects1']
+        filter_objs_second = ['second', 'filter2', 'objects2']
+        filter_objs_last = ['last', 'filter3', 'objects3']
+        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')
+        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(filter_objs_second)
+        Filter2().AndReturn(filt2_mock)
+        filt2_mock.filter_all(filter_objs_second,
+                              filter_properties).AndReturn(filter_objs_last)
+
+        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(result, filter_objs_last)