Do not print default dicts during heal_allocations

The verbose output of nova-manage placement heal_allocations --dry-run
contains nested default dicts. This makes the output hard to read.

This patch makes sure that such dicts are json dumped first to get rid
of the implementation specific default dict outputs.

Change-Id: I2dec02972b8d92eaf9ad14577b764a9f4ca4c49b

nova/cmd/manage.py

@@ -38,6 +38,7 @@ from oslo_config import cfg
 from oslo_db import exception as db_exc
 from oslo_log import log as logging
 import oslo_messaging as messaging
+from oslo_serialization import jsonutils
 from oslo_utils import encodeutils
 from oslo_utils import importutils
 from oslo_utils import uuidutils
@@ -2168,16 +2169,19 @@ class PlacementCommands(object):
 
         if need_healing:
             if dry_run:
+                # json dump the allocation dict as it contains nested default
+                # dicts that is pretty hard to read in the verbose output
+                alloc = jsonutils.dumps(allocations)
                 if need_healing == _CREATE:
                     output(_('[dry-run] Create allocations for instance '
                              '%(instance)s: %(allocations)s') %
                            {'instance': instance.uuid,
-                            'allocations': allocations})
+                            'allocations': alloc})
                 elif need_healing == _UPDATE:
                     output(_('[dry-run] Update allocations for instance '
                              '%(instance)s: %(allocations)s') %
                            {'instance': instance.uuid,
-                            'allocations': allocations})
+                            'allocations': alloc})
             else:
                 # First update ports in neutron. If any of those operations
                 # fail, then roll back the successful part of it and fail the

nova/tests/functional/test_nova_manage.py

@@ -880,6 +880,25 @@ class TestNovaManagePlacementHealPortAllocations(
             self.output.getvalue())
         self.assertEqual(0, result)
 
+    def test_heal_port_allocation_dry_run(self):
+        server, ports = self._create_server_with_missing_port_alloc(
+            [self.neutron.port_1])
+
+        # let's trigger a heal
+        result = self.cli.heal_allocations(
+            verbose=True, max_count=2, dry_run=True)
+
+        self._assert_placement_not_updated(server)
+        self._assert_ports_not_updated(ports)
+
+        self.assertIn(
+            '[dry-run] Update allocations for instance',
+            self.output.getvalue())
+        # Note that we had a issues by printing defaultdicts directly to the
+        # user in the past. So let's assert it does not happen any more.
+        self.assertNotIn('defaultdict', self.output.getvalue())
+        self.assertEqual(4, result)
+
     def test_no_healing_is_needed(self):
         """Test that the instance has a port that has allocations
         so nothing to be healed.