Zone scheduler added

nova/scheduler/zone.py

@@ -0,0 +1,58 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright (c) 2010 Openstack, LLC.
+# Copyright 2010 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# 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.
+
+"""
+Availability Zone Scheduler implementation
+"""
+
+import random
+
+from nova.scheduler import driver
+from nova import db
+
+
+class ZoneScheduler(driver.Scheduler):
+    """Implements Scheduler as a random node selector."""
+
+    def hosts_up_with_zone(self, context, topic, zone):
+        """Return the list of hosts that have a running service 
+        for topic and availability zone (if defined). 
+        """
+
+        if zone is None:
+            return self.hosts_up(context, topic)
+
+        services = db.service_get_all_by_topic(context, topic)
+        return [service.host
+                for service in services
+                if self.service_is_up(service)
+                and service.availability_zone == zone]
+
+
+    def schedule(self, context, topic, *_args, **_kwargs):
+        """Picks a host that is up at random in selected 
+        availability zone (if defined).
+        """
+
+        zone = _kwargs.get('availability_zone')
+        hosts = self.hosts_up_with_zone(context, topic, zone)
+        if not hosts:
+            raise driver.NoValidHost(_("No hosts found"))
+        return hosts[int(random.random() * len(hosts))]
+