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

   1 # Copyright 2013 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 import cPickle
   6 import google.appengine.ext.db as db
   7 import logging
   8 import traceback
   9
  10
  11 _MAX_ENTITY_SIZE = 1024*1024
  12
  13
  14 # A collection of the data store models used throughout the server.
  15 # These values are global within datastore.
  16
  17 class PersistentObjectStoreItem(db.Model):
  18   pickled_value = db.BlobProperty()
  19
  20   @classmethod
  21   def CreateKey(cls, namespace, key):
  22     path = '%s/%s' % (namespace, key)
  23     try:
  24       return db.Key.from_path(cls.__name__, path)
  25     except Exception:
  26       # Probably AppEngine's BadValueError for the name being too long, but
  27       # it's not documented which errors can actually be thrown here, so catch
  28       # 'em all.
  29       raise ValueError(
  30           'Exception thrown when trying to create db.Key from path %s: %s' % (
  31               path, traceback.format_exc()))
  32
  33   @classmethod
  34   def CreateItem(cls, namespace, key, value):
  35     pickled_value = cPickle.dumps(value)
  36     if len(pickled_value) > _MAX_ENTITY_SIZE:
  37       logging.warn('Refusing to create entity greater than 1 MB in size: %s/%s'
  38                    % (namespace, key))
  39       return None
  40     return PersistentObjectStoreItem(key=cls.CreateKey(namespace, key),
  41                                      pickled_value=pickled_value)
  42
  43   def GetValue(self):
  44     return cPickle.loads(self.pickled_value)