Use a custom id generator over uuid4

>>> timeit.timeit("uuid.uuid4()", setup="import uuid")
9.518647909164429
>>> timeit.timeit("get_unique_id()", setup="from __main__ import get_unique_id")
0.40436601638793945

This will mainly be beneficial when a very large inventory is being
used, however it may also help with some very large playbooks.

lib/ansible/inventory/host.py

@@ -19,10 +19,8 @@
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
-import uuid
-
 from ansible.inventory.group import Group
-from ansible.utils.vars import combine_vars
+from ansible.utils.vars import combine_vars, get_unique_id
 
 __all__ = ['Host']
 
@@ -92,7 +90,7 @@ class Host:
         self._gathered_facts = False
         self._uuid = None
         if gen_uuid:
-            self._uuid = uuid.uuid4()
+            self._uuid = get_unique_id()
         self.implicit = False
 
     def __repr__(self):

lib/ansible/playbook/base.py

@@ -21,7 +21,6 @@ __metaclass__ = type
 
 import itertools
 import operator
-import uuid
 
 from copy import copy as shallowcopy
 from functools import partial
@@ -34,7 +33,7 @@ from ansible.module_utils._text import to_text
 from ansible.playbook.attribute import Attribute, FieldAttribute
 from ansible.parsing.dataloader import DataLoader
 from ansible.constants import mk_boolean as boolean
-from ansible.utils.vars import combine_vars, isidentifier
+from ansible.utils.vars import combine_vars, isidentifier, get_unique_id
 
 try:
     from __main__ import display
@@ -184,7 +183,7 @@ class Base(with_metaclass(BaseMeta, object)):
         self._finalized = False
 
         # every object gets a random uuid:
-        self._uuid = uuid.uuid4()
+        self._uuid = get_unique_id()
 
         # we create a copy of the attributes here due to the fact that
         # it was intialized as a class param in the meta class, so we