sdk/python/arvados/cache.py

   1 # Copyright (C) The Arvados Authors. All rights reserved.
   2 #
   3 # SPDX-License-Identifier: Apache-2.0
   4
   5 from builtins import object
   6 import errno
   7 import hashlib
   8 import os
   9 import tempfile
  10 import time
  11
  12 class SafeHTTPCache(object):
  13     """Thread-safe replacement for httplib2.FileCache"""
  14
  15     def __init__(self, path=None, max_age=None):
  16         self._dir = path
  17         if max_age is not None:
  18             try:
  19                 self._clean(threshold=time.time() - max_age)
  20             except:
  21                 pass
  22
  23     def _clean(self, threshold=0):
  24         for ent in os.listdir(self._dir):
  25             fnm = os.path.join(self._dir, ent)
  26             if os.path.isdir(fnm) or not fnm.endswith('.tmp'):
  27                 continue
  28             stat = os.lstat(fnm)
  29             if stat.st_mtime < threshold:
  30                 try:
  31                     os.unlink(fnm)
  32                 except OSError as err:
  33                     if err.errno != errno.ENOENT:
  34                         raise
  35
  36     def __str__(self):
  37         return self._dir
  38
  39     def _filename(self, url):
  40         return os.path.join(self._dir, hashlib.md5(url.encode('utf-8')).hexdigest()+'.tmp')
  41
  42     def get(self, url):
  43         filename = self._filename(url)
  44         try:
  45             with open(filename, 'rb') as f:
  46                 return f.read()
  47         except (IOError, OSError):
  48             return None
  49
  50     def set(self, url, content):
  51         try:
  52             fd, tempname = tempfile.mkstemp(dir=self._dir)
  53         except:
  54             return None
  55         try:
  56             try:
  57                 f = os.fdopen(fd, 'wb')
  58             except:
  59                 os.close(fd)
  60                 raise
  61             try:
  62                 f.write(content)
  63             finally:
  64                 f.close()
  65             os.rename(tempname, self._filename(url))
  66             tempname = None
  67         finally:
  68             if tempname:
  69                 os.unlink(tempname)
  70
  71     def delete(self, url):
  72         try:
  73             os.unlink(self._filename(url))
  74         except OSError as err:
  75             if err.errno != errno.ENOENT:
  76                 raise