Refactored the HostFilterScheduler and LeastCostScheduler classes so that they can be combined into a single class that can do both host filtering and host weighting, allowing subclasses to override those processes as needed. Also renamed the ZoneAwareScheduler to AbstractScheduler, for two reasons: one, the 'zone-aware' designation was necessary when the zone code was being developed; now that it is part of nova, it is not an important distinction. Second, the 'Abstract' part clearly indicates that this is a class that is not designed to be used directly, but rather as the basis for specific scheduler subclasses.

5 files changed, 61 insertions, 73 deletions

diff --git a/nova/scheduler/zone_aware_scheduler.py b/nova/scheduler/abstract_scheduler.py
index d1924c9f9..eb924732a 100644
--- a/nova/scheduler/zone_aware_scheduler.py
+++ b/nova/scheduler/abstract_scheduler.py
@@ -14,7 +14,7 @@
 #    under the License.
 
 """
-The Zone Aware Scheduler is a base class Scheduler for creating instances
+The AbsractScheduler is a base class Scheduler for creating instances
 across zones. There are two expansion points to this class for:
 1. Assigning Weights to hosts for requested instances
 2. Filtering Hosts based on required instance capabilities
@@ -40,7 +40,7 @@ from nova.scheduler import api
 from nova.scheduler import driver
 
 FLAGS = flags.FLAGS
-LOG = logging.getLogger('nova.scheduler.zone_aware_scheduler')
+LOG = logging.getLogger('nova.scheduler.abstract_scheduler')
 
 
 class InvalidBlob(exception.NovaException):
@@ -48,8 +48,10 @@ class InvalidBlob(exception.NovaException):
                 "to instance create request.")
 
 
-class ZoneAwareScheduler(driver.Scheduler):
-    """Base class for creating Zone Aware Schedulers."""
+class AbstractScheduler(driver.Scheduler):
+    """Base class for creating Schedulers that can work across any nova
+    deployment, from simple designs to multiply-nested zones.
+    """
 
     def _call_zone_method(self, context, method, specs, zones):
         """Call novaclient zone method. Broken out for testing."""
@@ -266,7 +268,7 @@ class ZoneAwareScheduler(driver.Scheduler):
         """
 
         if topic != "compute":
-            raise NotImplementedError(_("Zone Aware Scheduler only understands"
+            raise NotImplementedError(_("Scheduler only understands"
                                         " Compute nodes (for now)"))
 
         num_instances = request_spec.get('num_instances', 1)
@@ -328,13 +330,31 @@ class ZoneAwareScheduler(driver.Scheduler):
         requested_mem = instance_type['memory_mb'] * 1024 * 1024
         return capabilities['host_memory_free'] >= requested_mem
 
+    def hold_filter_hosts(self, topic, request_spec, hosts=None):
+        """Filter the full host list (from the ZoneManager)"""
+        # NOTE(dabo): The logic used by the current _schedule() method
+        # is incorrect. Since this task is just to refactor the classes,
+        # I'm not fixing the logic now - that will be the next task.
+        # So for now this method is just renamed; afterwards this will
+        # become the filter_hosts() method, and the one below will
+        # be removed.
+        filter_name = request_spec.get('filter', None)
+        # Make sure that the requested filter is legitimate.
+        selected_filter = host_filter.choose_host_filter(filter_name)
+
+        # TODO(sandy): We're only using InstanceType-based specs
+        # currently. Later we'll need to snoop for more detailed
+        # host filter requests.
+        instance_type = request_spec['instance_type']
+        name, query = selected_filter.instance_type_to_filter(instance_type)
+        return selected_filter.filter_hosts(self.zone_manager, query)
+
     def filter_hosts(self, topic, request_spec, host_list=None):
         """Return a list of hosts which are acceptable for scheduling.
         Return value should be a list of (hostname, capability_dict)s.
         Derived classes may override this, but may find the
         '<topic>_filter' function more appropriate.
         """
-
         def _default_filter(self, hostname, capabilities, request_spec):
             """Default filter function if there's no <topic>_filter"""
             # NOTE(sirp): The default logic is the equivalent to
diff --git a/nova/scheduler/host_filter.py b/nova/scheduler/host_filter.py
index b7bbbbcb8..45a8f40d8 100644
--- a/nova/scheduler/host_filter.py
+++ b/nova/scheduler/host_filter.py
@@ -14,7 +14,12 @@
 #    under the License.
 
 """
-Host Filter is a mechanism for requesting instance resources.
+The Host Filter classes are a way to ensure that only hosts that are
+appropriate are considered when creating a new instance. Hosts that are
+either incompatible or insufficient to accept a newly-requested instance
+are removed by Host Filter classes from consideration. Those that pass
+the filter are then passed on for weighting or other process for ordering.
+
 Three filters are included: AllHosts, Flavor & JSON. AllHosts just
 returns the full, unfiltered list of hosts. Flavor is a hard coded
 matching mechanism based on flavor criteria and JSON is an ad-hoc
@@ -28,12 +33,6 @@ noted a need for a more expressive way of specifying instances.
 Since we don't want to get into building full DSL this is a simple
 form as an example of how this could be done. In reality, most
 consumers will use the more rigid filters such as FlavorFilter.
-
-Note: These are "required" capability filters. These capabilities
-used must be present or the host will be excluded. The hosts
-returned are then weighed by the Weighted Scheduler. Weights
-can take the more esoteric factors into consideration (such as
-server affinity and customer separation).
 """
 
 import json
@@ -41,9 +40,7 @@ import json
 from nova import exception
 from nova import flags
 from nova import log as logging
-from nova.scheduler import zone_aware_scheduler
 from nova import utils
-from nova.scheduler import zone_aware_scheduler
 
 LOG = logging.getLogger('nova.scheduler.host_filter')
 
@@ -125,9 +122,8 @@ class InstanceTypeFilter(HostFilter):
             spec_disk = instance_type['local_gb']
             extra_specs = instance_type['extra_specs']
 
-            if host_ram_mb >= spec_ram and \
-               disk_bytes >= spec_disk and \
-               self._satisfies_extra_specs(capabilities, instance_type):
+            if ((host_ram_mb >= spec_ram) and (disk_bytes >= spec_disk) and
+                    self._satisfies_extra_specs(capabilities, instance_type)):
                 selected_hosts.append((host, capabilities))
         return selected_hosts
 
@@ -309,7 +305,6 @@ def choose_host_filter(filter_name=None):
     function checks the filter name against a predefined set
     of acceptable filters.
     """
-
     if not filter_name:
         filter_name = FLAGS.default_host_filter
     for filter_class in FILTERS:
@@ -317,33 +312,3 @@ def choose_host_filter(filter_name=None):
         if host_match == filter_name:
             return filter_class()
     raise exception.SchedulerHostFilterNotFound(filter_name=filter_name)
-
-
-class HostFilterScheduler(zone_aware_scheduler.ZoneAwareScheduler):
-    """The HostFilterScheduler uses the HostFilter to filter
-    hosts for weighing. The particular filter used may be passed in
-    as an argument or the default will be used.
-
-    request_spec = {'filter': <Filter name>,
-                    'instance_type': <InstanceType dict>}
-    """
-
-    def filter_hosts(self, topic, request_spec, hosts=None):
-        """Filter the full host list (from the ZoneManager)"""
-
-        filter_name = request_spec.get('filter', None)
-        host_filter = choose_host_filter(filter_name)
-
-        # TODO(sandy): We're only using InstanceType-based specs
-        # currently. Later we'll need to snoop for more detailed
-        # host filter requests.
-        instance_type = request_spec['instance_type']
-        name, query = host_filter.instance_type_to_filter(instance_type)
-        return host_filter.filter_hosts(self.zone_manager, query)
-
-    def weigh_hosts(self, topic, request_spec, hosts):
-        """Derived classes must override this method and return
-        a lists of hosts in [{weight, hostname}] format.
-        """
-        return [dict(weight=1, hostname=hostname, capabilities=caps)
-                for hostname, caps in hosts]
diff --git a/nova/scheduler/least_cost.py b/nova/scheduler/least_cost.py
index 329107efe..a58b11289 100644
--- a/nova/scheduler/least_cost.py
+++ b/nova/scheduler/least_cost.py
@@ -22,11 +22,14 @@ The cost-function and weights are tabulated, and the host with the least cost
 is then selected for provisioning.
 """
 
+# TODO(dabo): This class will be removed in the next merge prop; it remains now
+# because much of the code will be refactored into different classes.
+
 import collections
 
 from nova import flags
 from nova import log as logging
-from nova.scheduler import zone_aware_scheduler
+from nova.scheduler import abstract_scheduler
 from nova import utils
 from nova import exception
 
@@ -61,7 +64,7 @@ def compute_fill_first_cost_fn(host):
     return free_mem
 
 
-class LeastCostScheduler(zone_aware_scheduler.ZoneAwareScheduler):
+class LeastCostScheduler(abstract_scheduler.AbstractScheduler):
     def __init__(self, *args, **kwargs):
         self.cost_fns_cache = {}
         super(LeastCostScheduler, self).__init__(*args, **kwargs)
diff --git a/nova/tests/scheduler/test_zone_aware_scheduler.py b/nova/tests/scheduler/test_abstract_scheduler.py
index 788efca52..f4f5cc233 100644
--- a/nova/tests/scheduler/test_zone_aware_scheduler.py
+++ b/nova/tests/scheduler/test_abstract_scheduler.py
@@ -13,7 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 """
-Tests For Zone Aware Scheduler.
+Tests For Abstract Scheduler.
 """
 
 import json
@@ -25,7 +25,7 @@ from nova import rpc
 from nova import test
 from nova.compute import api as compute_api
 from nova.scheduler import driver
-from nova.scheduler import zone_aware_scheduler
+from nova.scheduler import abstract_scheduler
 from nova.scheduler import zone_manager
 
 
@@ -60,7 +60,7 @@ def fake_zone_manager_service_states(num_hosts):
     return states
 
 
-class FakeZoneAwareScheduler(zone_aware_scheduler.ZoneAwareScheduler):
+class FakeAbstractScheduler(abstract_scheduler.AbstractScheduler):
     # No need to stub anything at the moment
     pass
 
@@ -161,15 +161,15 @@ def fake_zone_get_all(context):
     ]
 
 
-class ZoneAwareSchedulerTestCase(test.TestCase):
-    """Test case for Zone Aware Scheduler."""
+class AbstractSchedulerTestCase(test.TestCase):
+    """Test case for Abstract Scheduler."""
 
-    def test_zone_aware_scheduler(self):
+    def test_abstract_scheduler(self):
         """
         Create a nested set of FakeZones, try to build multiple instances
         and ensure that a select call returns the appropriate build plan.
         """
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         self.stubs.Set(sched, '_call_zone_method', fake_call_zone_method)
         self.stubs.Set(nova.db, 'zone_get_all', fake_zone_get_all)
 
@@ -194,7 +194,7 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
         properly adjusted based on the scale/offset in the zone
         db entries.
         """
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         child_results = fake_call_zone_method(None, None, None, None)
         zones = fake_zone_get_all(None)
         sched._adjust_child_weights(child_results, zones)
@@ -209,11 +209,11 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
                 if zone == 'zone3':  # Scale x1000
                     self.assertEqual(scaled.pop(0), w)
 
-    def test_empty_zone_aware_scheduler(self):
+    def test_empty_abstract_scheduler(self):
         """
         Ensure empty hosts & child_zones result in NoValidHosts exception.
         """
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         self.stubs.Set(sched, '_call_zone_method', fake_empty_call_zone_method)
         self.stubs.Set(nova.db, 'zone_get_all', fake_zone_get_all)
 
@@ -231,7 +231,7 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
         If the zone_blob hint was passed in, don't re-schedule.
         """
         global was_called
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         was_called = False
         self.stubs.Set(sched, '_provision_resource', fake_provision_resource)
         request_spec = {
@@ -248,7 +248,7 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
     def test_provision_resource_local(self):
         """Provision a resource locally or remotely."""
         global was_called
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         was_called = False
         self.stubs.Set(sched, '_provision_resource_locally',
                        fake_provision_resource_locally)
@@ -260,7 +260,7 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
     def test_provision_resource_remote(self):
         """Provision a resource locally or remotely."""
         global was_called
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         was_called = False
         self.stubs.Set(sched, '_provision_resource_from_blob',
                        fake_provision_resource_from_blob)
@@ -272,9 +272,9 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
     def test_provision_resource_from_blob_empty(self):
         """Provision a resource locally or remotely given no hints."""
         global was_called
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         request_spec = {}
-        self.assertRaises(zone_aware_scheduler.InvalidBlob,
+        self.assertRaises(abstract_scheduler.InvalidBlob,
                           sched._provision_resource_from_blob,
                           None, {}, 1, {}, {})
 
@@ -283,7 +283,7 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
         Provision a resource locally or remotely when blob hint passed in.
         """
         global was_called
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         was_called = False
 
         def fake_create_db_entry_for_new_instance(self, context,
@@ -317,7 +317,7 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
         passed in.
         """
         global was_called
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         self.stubs.Set(sched, '_decrypt_blob',
                        fake_decrypt_blob_returns_child_info)
         was_called = False
@@ -336,7 +336,7 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
         from an immediate child.
         """
         global was_called
-        sched = FakeZoneAwareScheduler()
+        sched = FakeAbstractScheduler()
         was_called = False
         self.stubs.Set(sched, '_ask_child_zone_to_create_instance',
                        fake_ask_child_zone_to_create_instance)
@@ -350,14 +350,14 @@ class ZoneAwareSchedulerTestCase(test.TestCase):
     def test_decrypt_blob(self):
         """Test that the decrypt method works."""
 
-        fixture = FakeZoneAwareScheduler()
+        fixture = FakeAbstractScheduler()
         test_data = {"foo": "bar"}
 
         class StubDecryptor(object):
             def decryptor(self, key):
                 return lambda blob: blob
 
-        self.stubs.Set(zone_aware_scheduler, 'crypto',
+        self.stubs.Set(abstract_scheduler, 'crypto',
                        StubDecryptor())
 
         self.assertEqual(fixture._decrypt_blob(test_data),
diff --git a/nova/tests/scheduler/test_least_cost_scheduler.py b/nova/tests/scheduler/test_least_cost_scheduler.py
index fbe6b2f77..de7581d0a 100644
--- a/nova/tests/scheduler/test_least_cost_scheduler.py
+++ b/nova/tests/scheduler/test_least_cost_scheduler.py
@@ -18,7 +18,7 @@ Tests For Least Cost Scheduler
 
 from nova import test
 from nova.scheduler import least_cost
-from nova.tests.scheduler import test_zone_aware_scheduler
+from nova.tests.scheduler import test_abstract_scheduler
 
 MB = 1024 * 1024
 
@@ -70,7 +70,7 @@ class LeastCostSchedulerTestCase(test.TestCase):
 
         zone_manager = FakeZoneManager()
 
-        states = test_zone_aware_scheduler.fake_zone_manager_service_states(
+        states = test_abstract_scheduler.fake_zone_manager_service_states(
             num_hosts=10)
         zone_manager.service_states = states