Implemented automatic caching for the discovery documents.
diff --git a/googleapiclient/discovery_cache/__init__.py b/googleapiclient/discovery_cache/__init__.py
new file mode 100644
index 0000000..c56fd65
--- /dev/null
+++ b/googleapiclient/discovery_cache/__init__.py
@@ -0,0 +1,42 @@
+# Copyright 2014 Google Inc. All Rights Reserved.
+#
+# 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.
+
+"""Caching utility for the discovery document."""
+
+from __future__ import absolute_import
+
+import logging
+import datetime
+
+DISCOVERY_DOC_MAX_AGE = 60 * 60 * 24 # 1 day
+
+
+def autodetect():
+ """Detects an appropriate cache module and returns it.
+
+ Returns:
+ googleapiclient.discovery_cache.base.Cache, a cache object which
+ is auto detected, or None if no cache object is available.
+ """
+ try:
+ from google.appengine.api import memcache
+ from . import appengine_memcache
+ return appengine_memcache.cache
+ except Exception:
+ try:
+ from . import file_cache
+ return file_cache.cache
+ except Exception as e:
+ logging.warning(e, exc_info=True)
+ return None
diff --git a/googleapiclient/discovery_cache/appengine_memcache.py b/googleapiclient/discovery_cache/appengine_memcache.py
new file mode 100644
index 0000000..a521fc3
--- /dev/null
+++ b/googleapiclient/discovery_cache/appengine_memcache.py
@@ -0,0 +1,52 @@
+# Copyright 2014 Google Inc. All Rights Reserved.
+#
+# 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.
+
+"""App Engine memcache based cache for the discovery document."""
+
+import logging
+
+# This is only an optional dependency because we only import this
+# module when google.appengine.api.memcache is available.
+from google.appengine.api import memcache
+
+from . import base
+from ..discovery_cache import DISCOVERY_DOC_MAX_AGE
+
+NAMESPACE = 'google-api-client'
+
+
+class Cache(base.Cache):
+ """A cache with app engine memcache API."""
+
+ def __init__(self, max_age):
+ """Constructor.
+
+ Args:
+ max_age: Cache expiration in seconds.
+ """
+ self._max_age = max_age
+
+ def get(self, url):
+ try:
+ return memcache.get(url, namespace=NAMESPACE)
+ except Exception as e:
+ logging.warning(e, exc_info=True)
+
+ def set(self, url, content):
+ try:
+ memcache.set(url, content, time=int(self._max_age), namespace=NAMESPACE)
+ except Exception as e:
+ logging.warning(e, exc_info=True)
+
+cache = Cache(max_age=DISCOVERY_DOC_MAX_AGE)
diff --git a/googleapiclient/discovery_cache/base.py b/googleapiclient/discovery_cache/base.py
new file mode 100644
index 0000000..00e466d
--- /dev/null
+++ b/googleapiclient/discovery_cache/base.py
@@ -0,0 +1,45 @@
+# Copyright 2014 Google Inc. All Rights Reserved.
+#
+# 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.
+
+"""An abstract class for caching the discovery document."""
+
+import abc
+
+
+class Cache(object):
+ """A base abstract cache class."""
+ __metaclass__ = abc.ABCMeta
+
+ @abc.abstractmethod
+ def get(self, url):
+ """Gets the content from the memcache with a given key.
+
+ Args:
+ url: string, the key for the cache.
+
+ Returns:
+ object, the value in the cache for the given key, or None if the key is
+ not in the cache.
+ """
+ raise NotImplementedError()
+
+ @abc.abstractmethod
+ def set(self, url, content):
+ """Sets the given key and content in the cache.
+
+ Args:
+ url: string, the key for the cache.
+ content: string, the discovery document.
+ """
+ raise NotImplementedError()
diff --git a/googleapiclient/discovery_cache/file_cache.py b/googleapiclient/discovery_cache/file_cache.py
new file mode 100644
index 0000000..ce540f0
--- /dev/null
+++ b/googleapiclient/discovery_cache/file_cache.py
@@ -0,0 +1,132 @@
+# Copyright 2014 Google Inc. All Rights Reserved.
+#
+# 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.
+
+"""File based cache for the discovery document.
+
+The cache is stored in a single file so that multiple processes can
+share the same cache. It locks the file whenever accesing to the
+file. When the cache content is corrupted, it will be initialized with
+an empty cache.
+"""
+
+from __future__ import division
+
+import datetime
+import json
+import logging
+import os
+import tempfile
+import threading
+
+from oauth2client.locked_file import LockedFile
+
+from . import base
+from ..discovery_cache import DISCOVERY_DOC_MAX_AGE
+
+logger = logging.getLogger(__name__)
+
+FILENAME = 'google-api-python-client-discovery-doc.cache'
+EPOCH = datetime.datetime.utcfromtimestamp(0)
+
+
+def _to_timestamp(date):
+ try:
+ return (date - EPOCH).total_seconds()
+ except AttributeError:
+ # The following is the equivalent of total_seconds() in Python2.6.
+ # See also: https://docs.python.org/2/library/datetime.html
+ delta = date - EPOCH
+ return ((delta.microseconds + (delta.seconds + delta.days * 24 * 3600)
+ * 10**6) / 10**6)
+
+
+def _read_or_initialize_cache(f):
+ f.file_handle().seek(0)
+ try:
+ cache = json.load(f.file_handle())
+ except Exception:
+ # This means it opens the file for the first time, or the cache is
+ # corrupted, so initializing the file with an empty dict.
+ cache = {}
+ f.file_handle().truncate(0)
+ f.file_handle().seek(0)
+ json.dump(cache, f.file_handle())
+ return cache
+
+
+class Cache(base.Cache):
+ """A file based cache for the discovery documents."""
+
+ def __init__(self, max_age):
+ """Constructor.
+
+ Args:
+ max_age: Cache expiration in seconds.
+ """
+ self._max_age = max_age
+ self._file = os.path.join(tempfile.gettempdir(), FILENAME)
+ f = LockedFile(self._file, 'a+', 'r')
+ try:
+ f.open_and_lock()
+ if f.is_locked():
+ _read_or_initialize_cache(f)
+ # If we can not obtain the lock, other process or thread must
+ # have initialized the file.
+ except Exception as e:
+ logging.warning(e, exc_info=True)
+ finally:
+ f.unlock_and_close()
+
+ def get(self, url):
+ f = LockedFile(self._file, 'r+', 'r')
+ try:
+ f.open_and_lock()
+ if f.is_locked():
+ cache = _read_or_initialize_cache(f)
+ if url in cache:
+ content, t = cache.get(url, (None, 0))
+ if _to_timestamp(datetime.datetime.now()) < t + self._max_age:
+ return content
+ return None
+ else:
+ logger.debug('Could not obtain a lock for the cache file.')
+ return None
+ except Exception as e:
+ logger.warning(e, exc_info=True)
+ finally:
+ f.unlock_and_close()
+
+ def set(self, url, content):
+ f = LockedFile(self._file, 'r+', 'r')
+ try:
+ f.open_and_lock()
+ if f.is_locked():
+ cache = _read_or_initialize_cache(f)
+ cache[url] = (content, _to_timestamp(datetime.datetime.now()))
+ # Remove stale cache.
+ for k, (_, timestamp) in list(cache.items()):
+ if _to_timestamp(datetime.datetime.now()) >= timestamp + self._max_age:
+ del cache[k]
+ f.file_handle().truncate(0)
+ f.file_handle().seek(0)
+ json.dump(cache, f.file_handle())
+ else:
+ logger.debug('Could not obtain a lock for the cache file.')
+ except Exception as e:
+ logger.warning(e, exc_info=True)
+ finally:
+ f.unlock_and_close()
+
+
+cache = Cache(max_age=DISCOVERY_DOC_MAX_AGE)