add hypervisor version weigher

implements: blueprint weigh-host-by-hypervisor-version
Change-Id: I36b16a388383c26bdf432030bc9e28b2fd75d120

1 files changed, 39 insertions, 0 deletions

diff --git a/nova/scheduler/weights/hypervisor_version.py b/nova/scheduler/weights/hypervisor_version.py
new file mode 100644
index 0000000000..0cd7b0a824
--- /dev/null
+++ b/nova/scheduler/weights/hypervisor_version.py
@@ -0,0 +1,39 @@
+#    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.
+
+"""
+Hypervisor Version Weigher. Weigh hosts by their relative hypervior version.
+
+The default is to select newer hosts.  If you prefer
+to invert the behavior set the 'hypervisor_version_weight_multiplier' option
+to a negative number and the weighing has the opposite effect of the default.
+"""
+
+import nova.conf
+from nova.scheduler import utils
+from nova.scheduler import weights
+
+CONF = nova.conf.CONF
+
+
+class HypervisorVersionWeigher(weights.BaseHostWeigher):
+
+    def weight_multiplier(self, host_state):
+        """Override the weight multiplier."""
+        return utils.get_weight_multiplier(
+            host_state, 'hypervisor_version_weight_multiplier',
+            CONF.filter_scheduler.hypervisor_version_weight_multiplier)
+
+    def _weigh_object(self, host_state, weight_properties):
+        """Higher weights win.  We want newer hosts by default."""
+        # convert None to 0
+        return host_state.hypervisor_version or 0