Adds to Melange a tags framework based on taggable-mixin.
The taggable-mixin allowed only tag per Datastore model. This is extended
framework allows any arbitrary number of tags per Datastore model. Also,
now one can define different models for different Tag types which are all
inherited from the base Tag model provided by taggable-mixin.
The GHOPTask model makes use of 2 tags per model, one for difficulty and the
other for task_type, both using the tags framework.
Reviewed by: Paweł Sołyga
"Thread-safe in-memory cache backend."
import time
try:
import cPickle as pickle
except ImportError:
import pickle
from django.core.cache.backends.base import BaseCache
from django.utils.synch import RWLock
class CacheClass(BaseCache):
def __init__(self, _, params):
BaseCache.__init__(self, params)
self._cache = {}
self._expire_info = {}
max_entries = params.get('max_entries', 300)
try:
self._max_entries = int(max_entries)
except (ValueError, TypeError):
self._max_entries = 300
cull_frequency = params.get('cull_frequency', 3)
try:
self._cull_frequency = int(cull_frequency)
except (ValueError, TypeError):
self._cull_frequency = 3
self._lock = RWLock()
def add(self, key, value, timeout=None):
self._lock.writer_enters()
try:
exp = self._expire_info.get(key)
if exp is None or exp <= time.time():
try:
self._set(key, pickle.dumps(value), timeout)
return True
except pickle.PickleError:
pass
return False
finally:
self._lock.writer_leaves()
def get(self, key, default=None):
self._lock.reader_enters()
try:
exp = self._expire_info.get(key)
if exp is None:
return default
elif exp > time.time():
try:
return pickle.loads(self._cache[key])
except pickle.PickleError:
return default
finally:
self._lock.reader_leaves()
self._lock.writer_enters()
try:
del self._cache[key]
del self._expire_info[key]
return default
finally:
self._lock.writer_leaves()
def _set(self, key, value, timeout=None):
if len(self._cache) >= self._max_entries:
self._cull()
if timeout is None:
timeout = self.default_timeout
self._cache[key] = value
self._expire_info[key] = time.time() + timeout
def set(self, key, value, timeout=None):
self._lock.writer_enters()
# Python 2.3 and 2.4 don't allow combined try-except-finally blocks.
try:
try:
self._set(key, pickle.dumps(value), timeout)
except pickle.PickleError:
pass
finally:
self._lock.writer_leaves()
def has_key(self, key):
self._lock.reader_enters()
try:
exp = self._expire_info.get(key)
if exp is None:
return False
elif exp > time.time():
return True
finally:
self._lock.reader_leaves()
self._lock.writer_enters()
try:
del self._cache[key]
del self._expire_info[key]
return False
finally:
self._lock.writer_leaves()
def _cull(self):
if self._cull_frequency == 0:
self._cache.clear()
self._expire_info.clear()
else:
doomed = [k for (i, k) in enumerate(self._cache) if i % self._cull_frequency == 0]
for k in doomed:
self._delete(k)
def _delete(self, key):
try:
del self._cache[key]
except KeyError:
pass
try:
del self._expire_info[key]
except KeyError:
pass
def delete(self, key):
self._lock.writer_enters()
try:
self._delete(key)
finally:
self._lock.writer_leaves()