Make RingBuilders deep-copy-able

We used to be able to deep-copy RingBuilder objects, but the addition
of debug logging (8d3b3b2) broke that since you can't deep-copy a
Python logger. This commit fixes that.

Swift doesn't really deep-copy RingBuilders anywhere, but third-party
code might.

Change-Id: If8bdadd93d9980db3d8a093f32d76ca604de9301

swift/cli/ringbuilder.py

@@ -1073,8 +1073,7 @@ def write_builder():
             '_last_part_gather_start': 0,
             '_remove_devs': [],
         }
-        builder = RingBuilder(1, 1, 1)
-        builder.copy_from(builder_dict)
+        builder = RingBuilder.from_dict(builder_dict)
         for parts in builder._replica2part2dev:
             for dev_id in parts:
                 builder.devs[dev_id]['parts'] += 1

swift/common/ring/builder.py

@@ -21,6 +21,7 @@
 import math
 import random
 import cPickle as pickle
+from copy import deepcopy
 
 from array import array
 from collections import defaultdict
@@ -125,6 +126,12 @@ def weight_of_one_part(self):
                                             'ring, or all devices have been '
                                             'deleted')
 
+    @classmethod
+    def from_dict(cls, builder_data):
+        b = cls(1, 1, 1)  # Dummy values
+        b.copy_from(builder_data)
+        return b
+
     def copy_from(self, builder):
         """
         Reinitializes this RingBuilder instance from data obtained from the
@@ -173,6 +180,11 @@ def copy_from(self, builder):
         for dev in self._iter_devs():
             dev.setdefault("region", 1)
 
+    def __deepcopy__(self, memo):
+        the_copy = type(self).from_dict(deepcopy(self.to_dict(), memo))
+        memo[id(self)] = the_copy
+        return the_copy
+
     def to_dict(self):
         """
         Returns a dict that can be used later with copy_from to

test/unit/common/ring/test_builder.py

@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import copy
 import errno
 import mock
 import operator
@@ -84,6 +85,26 @@ def test_negative_min_part_hours(self):
         ring.RingBuilder(8, 3, 0)  # passes by not crashing
         self.assertRaises(ValueError, ring.RingBuilder, 8, 3, -1)
 
+    def test_deepcopy(self):
+        rb = ring.RingBuilder(8, 3, 1)
+        rb.add_dev({'id': 0, 'region': 0, 'zone': 0, 'weight': 1,
+                    'ip': '127.0.0.1', 'port': 10000, 'device': 'sda1'})
+        rb.add_dev({'id': 1, 'region': 0, 'zone': 1, 'weight': 1,
+                    'ip': '127.0.0.1', 'port': 10001, 'device': 'sda1'})
+        rb.add_dev({'id': 2, 'region': 0, 'zone': 2, 'weight': 1,
+                    'ip': '127.0.0.1', 'port': 10002, 'device': 'sda1'})
+        rb.add_dev({'id': 3, 'region': 0, 'zone': 1, 'weight': 1,
+                    'ip': '127.0.0.1', 'port': 10004, 'device': 'sda1'})
+        rb.rebalance()
+        rb_copy = copy.deepcopy(rb)
+
+        self.assertEqual(rb.to_dict(), rb_copy.to_dict())
+        self.assertTrue(rb.devs is not rb_copy.devs)
+        self.assertTrue(rb._replica2part2dev is not rb_copy._replica2part2dev)
+        self.assertTrue(rb._last_part_moves is not rb_copy._last_part_moves)
+        self.assertTrue(rb._remove_devs is not rb_copy._remove_devs)
+        self.assertTrue(rb._dispersion_graph is not rb_copy._dispersion_graph)
+
     def test_get_ring(self):
         rb = ring.RingBuilder(8, 3, 1)
         rb.add_dev({'id': 0, 'region': 0, 'zone': 0, 'weight': 1,