Controller-side module caching.

This makes our recursive, ast.parse performance measures as fast as
pre-ziploader baseline.

Since this unittest isn't testing that the returned module data is
correct we don't need to worry about os.rename not having any module
data.  Should devise a separate test for the module and caching code

lib/ansible/plugins/strategy/__init__.py

@@ -19,15 +19,16 @@
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
-from ansible.compat.six.moves import queue as Queue
-from ansible.compat.six import iteritems, text_type, string_types
-
 import json
 import time
 import zlib
+from collections import defaultdict
+from multiprocessing import Lock
 
 from jinja2.exceptions import UndefinedError
 
+from ansible.compat.six.moves import queue as Queue
+from ansible.compat.six import iteritems, text_type, string_types
 from ansible import constants as C
 from ansible.errors import AnsibleError, AnsibleParserError, AnsibleUndefinedVariable
 from ansible.executor.play_iterator import PlayIterator
@@ -51,6 +52,8 @@ except ImportError:
 
 __all__ = ['StrategyBase']
 
+action_write_locks = defaultdict(Lock)
+
 
 # TODO: this should probably be in the plugins/__init__.py, with
 #       a smarter mechanism to set all of the attributes based on
@@ -141,6 +144,20 @@ class StrategyBase:
 
         display.debug("entering _queue_task() for %s/%s" % (host, task))
 
+         # Add a write lock for tasks.
+         # Maybe this should be added somewhere further up the call stack but
+         # this is the earliest in the code where we have task (1) extracted
+         # into its own variable and (2) there's only a single code path
+         # leading to the module being run.  This is called by three
+         # functions: __init__.py::_do_handler_run(), linear.py::run(), and
+         # free.py::run() so we'd have to add to all three to do it there.
+         # The next common higher level is __init__.py::run() and that has
+         # tasks inside of play_iterator so we'd have to extract them to do it
+         # there.
+        if not action_write_locks[task.action]:
+            display.warning('Python defaultdict did not create the Lock for us.  Creating manually')
+            action_write_locks[task.action] = Lock()
+
         # and then queue the new task
         display.debug("%s - putting task (%s) in queue" % (host, task))
         try: