Package googleapiclient :: Package discovery_cache :: Module file_cache
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Source Code for Module googleapiclient.discovery_cache.file_cache

  1  # Copyright 2014 Google Inc. All Rights Reserved. 
  2  # 
  3  # Licensed under the Apache License, Version 2.0 (the "License"); 
  4  # you may not use this file except in compliance with the License. 
  5  # You may obtain a copy of the License at 
  6  # 
  7  #      http://www.apache.org/licenses/LICENSE-2.0 
  8  # 
  9  # Unless required by applicable law or agreed to in writing, software 
 10  # distributed under the License is distributed on an "AS IS" BASIS, 
 11  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 12  # See the License for the specific language governing permissions and 
 13  # limitations under the License. 
 14   
 15  """File based cache for the discovery document. 
 16   
 17  The cache is stored in a single file so that multiple processes can 
 18  share the same cache. It locks the file whenever accesing to the 
 19  file. When the cache content is corrupted, it will be initialized with 
 20  an empty cache. 
 21  """ 
 22   
 23  from __future__ import division 
 24   
 25  import datetime 
 26  import json 
 27  import logging 
 28  import os 
 29  import tempfile 
 30  import threading 
 31   
 32  try: 
 33      from oauth2client.contrib.locked_file import LockedFile 
 34  except ImportError: 
 35      # oauth2client < 2.0.0 
 36      try: 
 37          from oauth2client.locked_file import LockedFile 
 38      except ImportError: 
 39          # oauth2client > 4.0.0 or google-auth 
 40          raise ImportError( 
 41              "file_cache is unavailable when using oauth2client >= 4.0.0 or google-auth" 
 42          ) 
 43   
 44  from . import base 
 45  from ..discovery_cache import DISCOVERY_DOC_MAX_AGE 
 46   
 47  LOGGER = logging.getLogger(__name__) 
 48   
 49  FILENAME = "google-api-python-client-discovery-doc.cache" 
 50  EPOCH = datetime.datetime.utcfromtimestamp(0) 
 51   
 52   
53 -def _to_timestamp(date):
54 try: 55 return (date - EPOCH).total_seconds() 56 except AttributeError: 57 # The following is the equivalent of total_seconds() in Python2.6. 58 # See also: https://docs.python.org/2/library/datetime.html 59 delta = date - EPOCH 60 return ( 61 delta.microseconds + (delta.seconds + delta.days * 24 * 3600) * 10 ** 6 62 ) / 10 ** 6
63 64
65 -def _read_or_initialize_cache(f):
66 f.file_handle().seek(0) 67 try: 68 cache = json.load(f.file_handle()) 69 except Exception: 70 # This means it opens the file for the first time, or the cache is 71 # corrupted, so initializing the file with an empty dict. 72 cache = {} 73 f.file_handle().truncate(0) 74 f.file_handle().seek(0) 75 json.dump(cache, f.file_handle()) 76 return cache
77 78
79 -class Cache(base.Cache):
80 """A file based cache for the discovery documents.""" 81
82 - def __init__(self, max_age):
83 """Constructor. 84 85 Args: 86 max_age: Cache expiration in seconds. 87 """ 88 self._max_age = max_age 89 self._file = os.path.join(tempfile.gettempdir(), FILENAME) 90 f = LockedFile(self._file, "a+", "r") 91 try: 92 f.open_and_lock() 93 if f.is_locked(): 94 _read_or_initialize_cache(f) 95 # If we can not obtain the lock, other process or thread must 96 # have initialized the file. 97 except Exception as e: 98 LOGGER.warning(e, exc_info=True) 99 finally: 100 f.unlock_and_close()
101
102 - def get(self, url):
103 f = LockedFile(self._file, "r+", "r") 104 try: 105 f.open_and_lock() 106 if f.is_locked(): 107 cache = _read_or_initialize_cache(f) 108 if url in cache: 109 content, t = cache.get(url, (None, 0)) 110 if _to_timestamp(datetime.datetime.now()) < t + self._max_age: 111 return content 112 return None 113 else: 114 LOGGER.debug("Could not obtain a lock for the cache file.") 115 return None 116 except Exception as e: 117 LOGGER.warning(e, exc_info=True) 118 finally: 119 f.unlock_and_close()
120
121 - def set(self, url, content):
122 f = LockedFile(self._file, "r+", "r") 123 try: 124 f.open_and_lock() 125 if f.is_locked(): 126 cache = _read_or_initialize_cache(f) 127 cache[url] = (content, _to_timestamp(datetime.datetime.now())) 128 # Remove stale cache. 129 for k, (_, timestamp) in list(cache.items()): 130 if ( 131 _to_timestamp(datetime.datetime.now()) 132 >= timestamp + self._max_age 133 ): 134 del cache[k] 135 f.file_handle().truncate(0) 136 f.file_handle().seek(0) 137 json.dump(cache, f.file_handle()) 138 else: 139 LOGGER.debug("Could not obtain a lock for the cache file.") 140 except Exception as e: 141 LOGGER.warning(e, exc_info=True) 142 finally: 143 f.unlock_and_close()
144 145 146 cache = Cache(max_age=DISCOVERY_DOC_MAX_AGE) 147