160 lines
4.5 KiB
Python
160 lines
4.5 KiB
Python
"File-based cache backend"
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import os
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import time
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import shutil
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try:
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import cPickle as pickle
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except ImportError:
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import pickle
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from django.core.cache.backends.base import BaseCache
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from django.utils.hashcompat import md5_constructor
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class CacheClass(BaseCache):
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def __init__(self, dir, params):
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BaseCache.__init__(self, params)
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max_entries = params.get('max_entries', 300)
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try:
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self._max_entries = int(max_entries)
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except (ValueError, TypeError):
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self._max_entries = 300
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cull_frequency = params.get('cull_frequency', 3)
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try:
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self._cull_frequency = int(cull_frequency)
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except (ValueError, TypeError):
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self._cull_frequency = 3
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self._dir = dir
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if not os.path.exists(self._dir):
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self._createdir()
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def add(self, key, value, timeout=None):
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if self.has_key(key):
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return False
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self.set(key, value, timeout)
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return True
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def get(self, key, default=None):
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fname = self._key_to_file(key)
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try:
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f = open(fname, 'rb')
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exp = pickle.load(f)
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now = time.time()
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if exp < now:
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f.close()
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self._delete(fname)
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else:
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return pickle.load(f)
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except (IOError, OSError, EOFError, pickle.PickleError):
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pass
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return default
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def set(self, key, value, timeout=None):
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fname = self._key_to_file(key)
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dirname = os.path.dirname(fname)
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if timeout is None:
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timeout = self.default_timeout
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self._cull()
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try:
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if not os.path.exists(dirname):
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os.makedirs(dirname)
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f = open(fname, 'wb')
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now = time.time()
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pickle.dump(now + timeout, f, pickle.HIGHEST_PROTOCOL)
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pickle.dump(value, f, pickle.HIGHEST_PROTOCOL)
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except (IOError, OSError):
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pass
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def delete(self, key):
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try:
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self._delete(self._key_to_file(key))
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except (IOError, OSError):
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pass
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def _delete(self, fname):
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os.remove(fname)
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try:
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# Remove the 2 subdirs if they're empty
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dirname = os.path.dirname(fname)
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os.rmdir(dirname)
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os.rmdir(os.path.dirname(dirname))
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except (IOError, OSError):
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pass
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def has_key(self, key):
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fname = self._key_to_file(key)
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try:
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f = open(fname, 'rb')
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exp = pickle.load(f)
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now = time.time()
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if exp < now:
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f.close()
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self._delete(fname)
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return False
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else:
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return True
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except (IOError, OSError, EOFError, pickle.PickleError):
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return False
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def _cull(self):
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if int(self._num_entries) < self._max_entries:
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return
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try:
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filelist = os.listdir(self._dir)
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except (IOError, OSError):
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return
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if self._cull_frequency == 0:
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doomed = filelist
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else:
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doomed = [os.path.join(self._dir, k) for (i, k) in enumerate(filelist) if i % self._cull_frequency == 0]
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for topdir in doomed:
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try:
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for root, _, files in os.walk(topdir):
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for f in files:
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self._delete(os.path.join(root, f))
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except (IOError, OSError):
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pass
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def _createdir(self):
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try:
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os.makedirs(self._dir)
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except OSError:
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raise EnvironmentError("Cache directory '%s' does not exist and could not be created'" % self._dir)
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def _key_to_file(self, key):
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"""
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Convert the filename into an md5 string. We'll turn the first couple
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bits of the path into directory prefixes to be nice to filesystems
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that have problems with large numbers of files in a directory.
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Thus, a cache key of "foo" gets turnned into a file named
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``{cache-dir}ac/bd/18db4cc2f85cedef654fccc4a4d8``.
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"""
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path = md5_constructor(key.encode('utf-8')).hexdigest()
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path = os.path.join(path[:2], path[2:4], path[4:])
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return os.path.join(self._dir, path)
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def _get_num_entries(self):
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count = 0
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for _,_,files in os.walk(self._dir):
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count += len(files)
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return count
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_num_entries = property(_get_num_entries)
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def clear(self):
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try:
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shutil.rmtree(self._dir)
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except (IOError, OSError):
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pass
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