Cell weighing class to handle mute child cells

Give negative weight to child cells that have not recently sent
capability or capacity updates to their parent cell.

Change-Id: I7cada3e1b6f04c48b71c82d8e0a8527e44674abd

1 files changed, 72 insertions, 0 deletions

diff --git a/nova/cells/weights/mute_child.py b/nova/cells/weights/mute_child.py
new file mode 100644
index 000000000..b8fd0570b
--- /dev/null
+++ b/nova/cells/weights/mute_child.py
@@ -0,0 +1,72 @@
+# Copyright (c) 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.
+
+"""
+If a child cell hasn't sent capacity or capability updates in a while,
+downgrade its likelihood of being chosen for scheduling requests.
+"""
+
+from oslo.config import cfg
+
+from nova.cells import weights
+from nova.openstack.common import log as logging
+from nova.openstack.common import timeutils
+
+LOG = logging.getLogger(__name__)
+
+mute_weigher_opts = [
+        cfg.FloatOpt('mute_weight_multiplier',
+                default=-10.0,
+                help='Multiplier used to weigh mute children.  (The value '
+                     'should be negative.)'),
+        cfg.FloatOpt('mute_weight_value',
+                default=1000.0,
+                help='Weight value assigned to mute children.  (The value '
+                     'should be positive.)'),
+         cfg.IntOpt("mute_child_interval",
+                default=300,
+                help='Number of seconds after which a lack of capability and '
+                     'capacity updates signals the child cell is to be '
+                     'treated as a mute.')
+]
+
+CONF = cfg.CONF
+CONF.register_opts(mute_weigher_opts, group='cells')
+
+
+class MuteChildWeigher(weights.BaseCellWeigher):
+    """If a child cell hasn't been heard from, greatly lower its selection
+    weight.
+    """
+
+    def _weight_multiplier(self):
+        # negative multiplier => lower weight
+        return CONF.cells.mute_weight_multiplier
+
+    def _weigh_object(self, cell, weight_properties):
+        """Check cell against the last_seen timestamp that indicates the time
+        that the most recent capability or capacity update was received from
+        the given cell."""
+
+        last_seen = cell.last_seen
+        secs = CONF.cells.mute_child_interval
+
+        if timeutils.is_older_than(last_seen, secs):
+            # yep, that's a mute child;  recommend highly that it be skipped!
+            LOG.warn(_("%(cell)s has not been seen since %(last_seen)s and is "
+                       "being treated as mute.") % locals())
+            return CONF.cells.mute_weight_value
+        else:
+            return 0