sdk/python/arvados/cache.py

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