Add existing GAM 3.21 code

gdata/analytics/alt/app_engine.py

@@ -0,0 +1,101 @@
+#!/usr/bin/python
+#
+# Copyright (C) 2009 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+"""Provides functions to persist serialized auth tokens in the datastore.
+
+The get_token and set_token functions should be used in conjunction with
+gdata.gauth's token_from_blob and token_to_blob to allow auth token objects
+to be reused across requests. It is up to your own code to ensure that the
+token key's are unique.
+"""
+
+__author__ = 'j.s@google.com (Jeff Scudder)'
+
+
+from google.appengine.ext import db
+from google.appengine.api import memcache
+
+
+class Token(db.Model):
+  """Datastore Model which stores a serialized auth token."""
+  t = db.BlobProperty()
+
+
+def get_token(unique_key):
+  """Searches for a stored token with the desired key.
+
+  Checks memcache and then the datastore if required.
+
+  Args:
+    unique_key: str which uniquely identifies the desired auth token.
+
+  Returns:
+    A string encoding the auth token data. Use gdata.gauth.token_from_blob to
+    convert back into a usable token object. None if the token was not found
+    in memcache or the datastore.
+  """
+  token_string = memcache.get(unique_key)
+  if token_string is None:
+    # The token wasn't in memcache, so look in the datastore.
+    token = Token.get_by_key_name(unique_key)
+    if token is None:
+      return None
+    return token.t
+  return token_string
+
+
+def set_token(unique_key, token_str):
+  """Saves the serialized auth token in the datastore.
+
+  The token is also stored in memcache to speed up retrieval on a cache hit.
+
+  Args:
+    unique_key: The unique name for this token as a string. It is up to your
+        code to ensure that this token value is unique in your application.
+        Previous values will be silently overwitten.
+    token_str: A serialized auth token as a string. I expect that this string
+        will be generated by gdata.gauth.token_to_blob.
+
+  Returns:
+    True if the token was stored sucessfully, False if the token could not be
+    safely cached (if an old value could not be cleared). If the token was
+    set in memcache, but not in the datastore, this function will return None.
+    However, in that situation an exception will likely be raised.
+
+  Raises:
+    Datastore exceptions may be raised from the App Engine SDK in the event of
+    failure.
+  """
+  # First try to save in memcache.
+  result = memcache.set(unique_key, token_str)
+  # If memcache fails to save the value, clear the cached value.
+  if not result:
+    result = memcache.delete(unique_key)
+    # If we could not clear the cached value for this token, refuse to save.
+    if result == 0:
+      return False
+  # Save to the datastore.
+  if Token(key_name=unique_key, t=token_str).put():
+    return True
+  return None
+
+
+def delete_token(unique_key):
+  # Clear from memcache.
+  memcache.delete(unique_key)
+  # Clear from the datastore.
+  Token(key_name=unique_key).delete()