120 lines
4.2 KiB
Python
120 lines
4.2 KiB
Python
"Memcached cache backend"
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import time
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from django.core.cache.backends.base import BaseCache, InvalidCacheBackendError
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try:
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import cmemcache as memcache
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import warnings
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warnings.warn(
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"Support for the 'cmemcache' library has been deprecated. Please use python-memcached instead.",
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DeprecationWarning
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)
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except ImportError:
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try:
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import memcache
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except:
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raise InvalidCacheBackendError("Memcached cache backend requires either the 'memcache' or 'cmemcache' library")
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class CacheClass(BaseCache):
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def __init__(self, server, params, key_prefix='', version=1, key_func=None):
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BaseCache.__init__(self, params, key_prefix, version, key_func)
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self._cache = memcache.Client(server.split(';'))
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def _get_memcache_timeout(self, timeout):
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"""
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Memcached deals with long (> 30 days) timeouts in a special
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way. Call this function to obtain a safe value for your timeout.
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"""
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timeout = timeout or self.default_timeout
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if timeout > 2592000: # 60*60*24*30, 30 days
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# See http://code.google.com/p/memcached/wiki/FAQ
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# "You can set expire times up to 30 days in the future. After that
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# memcached interprets it as a date, and will expire the item after
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# said date. This is a simple (but obscure) mechanic."
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#
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# This means that we have to switch to absolute timestamps.
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timeout += int(time.time())
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return timeout
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def add(self, key, value, timeout=0, version=None):
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key = self.make_key(key, version=version)
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if isinstance(value, unicode):
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value = value.encode('utf-8')
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return self._cache.add(key, value, self._get_memcache_timeout(timeout))
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def get(self, key, default=None, version=None):
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key = self.make_key(key, version=version)
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val = self._cache.get(key)
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if val is None:
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return default
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return val
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def set(self, key, value, timeout=0, version=None):
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key = self.make_key(key, version=version)
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self._cache.set(key, value, self._get_memcache_timeout(timeout))
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def delete(self, key, version=None):
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key = self.make_key(key, version=version)
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self._cache.delete(key)
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def get_many(self, keys, version=None):
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new_keys = map(lambda x: self.make_key(x, version=version), keys)
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ret = self._cache.get_multi(new_keys)
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if ret:
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_ = {}
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m = dict(zip(new_keys, keys))
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for k, v in ret.items():
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_[m[k]] = v
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ret = _
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return ret
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def close(self, **kwargs):
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self._cache.disconnect_all()
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def incr(self, key, delta=1, version=None):
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key = self.make_key(key, version=version)
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try:
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val = self._cache.incr(key, delta)
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# python-memcache responds to incr on non-existent keys by
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# raising a ValueError. Cmemcache returns None. In both
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# cases, we should raise a ValueError though.
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except ValueError:
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val = None
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if val is None:
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raise ValueError("Key '%s' not found" % key)
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return val
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def decr(self, key, delta=1, version=None):
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key = self.make_key(key, version=version)
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try:
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val = self._cache.decr(key, delta)
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# python-memcache responds to decr on non-existent keys by
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# raising a ValueError. Cmemcache returns None. In both
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# cases, we should raise a ValueError though.
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except ValueError:
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val = None
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if val is None:
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raise ValueError("Key '%s' not found" % key)
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return val
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def set_many(self, data, timeout=0, version=None):
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safe_data = {}
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for key, value in data.items():
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key = self.make_key(key, version=version)
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if isinstance(value, unicode):
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value = value.encode('utf-8')
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safe_data[key] = value
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self._cache.set_multi(safe_data, self._get_memcache_timeout(timeout))
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def delete_many(self, keys, version=None):
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l = lambda x: self.make_key(x, version=version)
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self._cache.delete_multi(map(l, keys))
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def clear(self):
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self._cache.flush_all()
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