sdk/python/arvados/cache.py

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