sdk/python/arvados/cache.py

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