Docserver: Persist stat cache for versioned file systems

chrome/common/extensions/docs/server2/memcache_object_store.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import logging
 
 from appengine_wrappers import memcache
+from future import Future
 from object_store import ObjectStore
 
 class _AsyncMemcacheGetFuture(object):
   def __init__(self, rpc):
     self._rpc = rpc
 
   def Get(self):
     return self._rpc.get_result()
 
 class MemcacheObjectStore(ObjectStore):
   def __init__(self, namespace):
     self._namespace = namespace
 
   def SetMulti(self, mapping):
     # talking_alarm_clock always fails because the zip is too big.
     # TODO(kalman): store example zips in blobstore.
     if any(key.find('talking_alarm_clock') != -1 for key in mapping.iterkeys()):
-      return
+      return Future(callback=lambda: None)
     try:
-      memcache.Client().set_multi_async(mapping, namespace=self._namespace)
+      rpc = memcache.Client().set_multi_async(mapping,
+          namespace=self._namespace)
+      return _AsyncMemcacheGetFuture(rpc)
     except ValueError as e:
       logging.error('Caught "ValueError: %s" when mapping keys %s' % (
           e, mapping.keys()))
 
   def GetMulti(self, keys):
     rpc = memcache.Client().get_multi_async(keys, namespace=self._namespace)
     return _AsyncMemcacheGetFuture(rpc)
 
   def DelMulti(self, keys):
     memcache.delete_multi(keys, namespace=self._namespace)