Merge "Refactor MigrationTask._execute"

nova/conductor/tasks/migrate.py

@@ -237,6 +237,40 @@ class MigrationTask(base.TaskBase):
         # pop the first alternate from the list to use for the destination, and
         # pass the remaining alternates to the compute.
         if self.host_list is None:
+            selection = self._schedule()
+
+        else:
+            # This is a reschedule that will use the supplied alternate hosts
+            # in the host_list as destinations.
+            selection = self._reschedule()
+
+        scheduler_utils.populate_filter_properties(legacy_props, selection)
+        # context is not serializable
+        legacy_props.pop('context', None)
+
+        (host, node) = (selection.service_host, selection.nodename)
+
+        self.instance.availability_zone = (
+            availability_zones.get_host_availability_zone(
+                self.context, host))
+
+        LOG.debug("Calling prep_resize with selected host: %s; "
+                  "Selected node: %s; Alternates: %s", host, node,
+                  self.host_list, instance=self.instance)
+        # RPC cast to the destination host to start the migration process.
+        self.compute_rpcapi.prep_resize(
+            # NOTE(mriedem): Using request_spec.image here is potentially
+            # dangerous if it is not kept up to date (i.e. rebuild/unshelve);
+            # seems like the sane thing to do would be to pass the current
+            # instance.image_meta since that is what MoveClaim will use for
+            # any NUMA topology claims on the destination host...
+            self.context, self.instance, self.request_spec.image,
+            self.flavor, host, migration,
+            request_spec=self.request_spec, filter_properties=legacy_props,
+            node=node, clean_shutdown=self.clean_shutdown,
+            host_list=self.host_list)
+
+    def _schedule(self):
         selection_lists = self.query_client.select_destinations(
             self.context, self.request_spec, [self.instance.uuid],
             return_objects=True, return_alternates=True)
@@ -249,16 +283,16 @@ class MigrationTask(base.TaskBase):
 
         scheduler_utils.fill_provider_mapping(
             self.context, self.reportclient, self.request_spec, selection)
+        return selection
 
-        else:
+    def _reschedule(self):
-            # This is a reschedule that will use the supplied alternate hosts
+        # Since the resources on these alternates may have been consumed and
-            # in the host_list as destinations. Since the resources on these
+        # might not be able to support the migrated instance, we need to first
-            # alternates may have been consumed and might not be able to
+        # claim the resources to verify the host still has sufficient
-            # support the migrated instance, we need to first claim the
+        # available resources.
-            # resources to verify the host still has sufficient availabile
-            # resources.
         elevated = self.context.elevated()
         host_available = False
+        selection = None
         while self.host_list and not host_available:
             selection = self.host_list.pop(0)
             if selection.allocation_request:
@@ -290,32 +324,7 @@ class MigrationTask(base.TaskBase):
                       "failures for instance %(instance_uuid)s." %
                       {"instance_uuid": self.instance.uuid})
             raise exception.MaxRetriesExceeded(reason=reason)
-
+        return selection
-        scheduler_utils.populate_filter_properties(legacy_props, selection)
-        # context is not serializable
-        legacy_props.pop('context', None)
-
-        (host, node) = (selection.service_host, selection.nodename)
-
-        self.instance.availability_zone = (
-            availability_zones.get_host_availability_zone(
-                self.context, host))
-
-        LOG.debug("Calling prep_resize with selected host: %s; "
-                  "Selected node: %s; Alternates: %s", host, node,
-                  self.host_list, instance=self.instance)
-        # RPC cast to the destination host to start the migration process.
-        self.compute_rpcapi.prep_resize(
-            # NOTE(mriedem): Using request_spec.image here is potentially
-            # dangerous if it is not kept up to date (i.e. rebuild/unshelve);
-            # seems like the sane thing to do would be to pass the current
-            # instance.image_meta since that is what MoveClaim will use for
-            # any NUMA topology claims on the destination host...
-            self.context, self.instance, self.request_spec.image,
-            self.flavor, host, migration,
-            request_spec=self.request_spec, filter_properties=legacy_props,
-            node=node, clean_shutdown=self.clean_shutdown,
-            host_list=self.host_list)
 
     def rollback(self):
         if self._migration: