Send 'create volume from snapshot' to the proper host

A simple solution for bug 1008866. When creating volume from snapshot on
multicluster, in volume it will check if snapshot_id is set. If snapshot_id
is set and FLAGS.snapshot_same_host is true, make the call create volume
directly to the volume host where the snapshot resides instead of passing it
through the scheduler. So snapshot can be copy to new volume. The same as
review 9761.

Change-Id: Ic182eb4563b9462704c5969d5116629442df316a

1 files changed, 37 insertions, 7 deletions

diff --git a/nova/volume/api.py b/nova/volume/api.py
index 90eef1e9c..a9ebeda28 100644
--- a/nova/volume/api.py
+++ b/nova/volume/api.py
@@ -25,13 +25,19 @@ import functools
 from nova.db import base
 from nova import exception
 from nova import flags
+from nova.openstack.common import cfg
 from nova.openstack.common import log as logging
 from nova.openstack.common import rpc
 from nova.openstack.common import timeutils
 import nova.policy
 from nova import quota
 
+volume_host_opt = cfg.BoolOpt('snapshot_same_host',
+        default=True,
+        help='Create volume from snapshot at the host where snapshot resides')
+
 FLAGS = flags.FLAGS
+FLAGS.register_opt(volume_host_opt)
 flags.DECLARE('storage_availability_zone', 'nova.volume.manager')
 
 LOG = logging.getLogger(__name__)
@@ -131,15 +137,39 @@ class API(base.Base):
             }
 
         volume = self.db.volume_create(context, options)
-        rpc.cast(context,
-                 FLAGS.scheduler_topic,
-                 {"method": "create_volume",
-                  "args": {"topic": FLAGS.volume_topic,
-                           "volume_id": volume['id'],
-                           "snapshot_id": snapshot_id,
-                           "reservations": reservations}})
+        self._cast_create_volume(context, volume['id'],
+                                 snapshot_id, reservations)
         return volume
 
+    def _cast_create_volume(self, context, volume_id,
+                            snapshot_id, reservations):
+
+        # NOTE(Rongze Zhu): It is a simple solution for bug 1008866
+        # If snapshot_id is set, make the call create volume directly to
+        # the volume host where the snapshot resides instead of passing it
+        # through the scheduer. So snapshot can be copy to new volume.
+
+        if snapshot_id and FLAGS.snapshot_same_host:
+            snapshot_ref = self.db.snapshot_get(context, snapshot_id)
+            src_volume_ref = self.db.volume_get(context,
+                                                snapshot_ref['volume_id'])
+            topic = rpc.queue_get_for(context,
+                                      FLAGS.volume_topic,
+                                      src_volume_ref['host'])
+            rpc.cast(context,
+                     topic,
+                     {"method": "create_volume",
+                      "args": {"volume_id": volume_id,
+                               "snapshot_id": snapshot_id}})
+        else:
+            rpc.cast(context,
+                     FLAGS.scheduler_topic,
+                     {"method": "create_volume",
+                      "args": {"topic": FLAGS.volume_topic,
+                               "volume_id": volume_id,
+                               "snapshot_id": snapshot_id,
+                               "reservations": reservations}})
+
     @wrap_check_policy
     def delete(self, context, volume):
         volume_id = volume['id']