Docserver: Persist stat cache for versioned file systems

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

 # Copyright 2014 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.
 
 from third_party.cloudstorage import cloudstorage_api
 from third_party.cloudstorage import common
 from third_party.cloudstorage import errors
 
 from docs_server_utils import StringIdentity
 from file_system import FileSystem, FileNotFoundError, StatInfo
@@ skipping 37 matching lines @@
   except errors.Error:
     raise FileNotFoundError('cloudstorage.listbucket failed for %s: %s' %
                             (dir_name, traceback.format_exc()))
 
 def _CreateStatInfo(bucket, path):
   full_path = Join(bucket, path)
   last_commit_file = Join(bucket, LAST_COMMIT_HASH_FILENAME)
   try:
     last_commit = _ReadFile(last_commit_file)
     if IsDirectory(full_path):
-      child_versions = dict((filename, last_commit) 
-                            for filename in _ListDir(full_path)) 
+      child_versions = dict((filename, last_commit)
+                            for filename in _ListDir(full_path))
     else:
       child_versions = None
     return StatInfo(last_commit, child_versions)
   except (TypeError, errors.Error):
     raise FileNotFoundError('cloudstorage.stat failed for %s: %s' % (path,
                             traceback.format_exc()))
 
 class CloudStorageFileSystem(FileSystem):
   '''FileSystem implementation which fetches resources from Google Cloud
   Storage.
@@ skipping 32 matching lines @@
     return Future(value=())
 
   def Stat(self, path):
     AssertIsValid(path)
     try:
       return _CreateStatInfo(self._bucket, path)
     except errors.AuthorizationError:
       self._warnAboutAuthError()
       raise
 
-  def GetIdentity(self):
+  def GetStableIdentity(self):
     return '@'.join((self.__class__.__name__, StringIdentity(self._bucket)))
 
   def __repr__(self):
     return 'CloudStorageFileSystem(%s)' % self._bucket
 
   def _warnAboutAuthError(self):
     logging.warn(('Authentication error on Cloud Storage. Check if your'
                   ' appengine project has permissions to Read the GCS'
                   ' buckets. If you are running a local appengine server,'
                   ' you need to set an access_token in'
                   ' local_debug/gcs_debug.conf.'
                   ' Remember that this token expires in less than 10'
                   ' minutes, so keep it updated. See'
                   ' gcs_file_system_provider.py for instructions.'));
     logging.debug(traceback.format_exc())