# -*- coding: utf-8 -*-
from __future__ import absolute_import
try:
import cPickle as pickle
except ImportError: # pragma: no cover
import pickle
from cachelib.base import BaseCache, _items
from cachelib._compat import string_types, integer_types
class RedisCache(BaseCache):
"""Uses the Redis key-value store as a cache backend.
The first argument can be either a string denoting address of the Redis
server or an object resembling an instance of a redis.Redis class.
Note: Python Redis API already takes care of encoding unicode strings on
the fly.
:param host: address of the Redis server or an object which API is
compatible with the official Python Redis client (redis-py).
:param port: port number on which Redis server listens for connections.
:param password: password authentication for the Redis server.
:param db: db (zero-based numeric index) on Redis Server to connect.
:param default_timeout: the default timeout that is used if no timeout is
specified on :meth:`~BaseCache.set`. A timeout of
0 indicates that the cache never expires.
:param key_prefix: A prefix that should be added to all keys.
Any additional keyword arguments will be passed to ``redis.Redis``.
"""
def __init__(self, host='localhost', port=6379, password=None,
db=0, default_timeout=300, key_prefix=None, **kwargs):
BaseCache.__init__(self, default_timeout)
if host is None:
raise ValueError('RedisCache host parameter may not be None')
if isinstance(host, string_types):
try:
import redis
except ImportError:
raise RuntimeError('no redis module found')
if kwargs.get('decode_responses', None):
raise ValueError('decode_responses is not supported by '
'RedisCache.')
self._client = redis.Redis(host=host, port=port, password=password,
db=db, **kwargs)
else:
self._client = host
self.key_prefix = key_prefix or ''
def _normalize_timeout(self, timeout):
timeout = BaseCache._normalize_timeout(self, timeout)
if timeout == 0:
timeout = -1
return timeout
def dump_object(self, value):
"""Dumps an object into a string for redis. By default it serializes
integers as regular string and pickle dumps everything else.
"""
t = type(value)
if t in integer_types:
return str(value).encode('ascii')
return b'!' + pickle.dumps(value)
def load_object(self, value):
"""The reversal of :meth:`dump_object`. This might be called with
None.
"""
if value is None:
return None
if value.startswith(b'!'):
try:
return pickle.loads(value[1:])
except pickle.PickleError:
return None
try:
return int(value)
except ValueError:
# before 0.8 we did not have serialization. Still support that.
return value
def get(self, key):
return self.load_object(self._client.get(self.key_prefix + key))
def get_many(self, *keys):
if self.key_prefix:
keys = [self.key_prefix + key for key in keys]
return [self.load_object(x) for x in self._client.mget(keys)]
def set(self, key, value, timeout=None):
timeout = self._normalize_timeout(timeout)
dump = self.dump_object(value)
if timeout == -1:
result = self._client.set(name=self.key_prefix + key,
value=dump)
else:
result = self._client.setex(name=self.key_prefix + key,
value=dump, time=timeout)
return result
def add(self, key, value, timeout=None):
timeout = self._normalize_timeout(timeout)
dump = self.dump_object(value)
return (
self._client.setnx(name=self.key_prefix + key, value=dump) and
self._client.expire(name=self.key_prefix + key, time=timeout)
)
def set_many(self, mapping, timeout=None):
timeout = self._normalize_timeout(timeout)
# Use transaction=False to batch without calling redis MULTI
# which is not supported by twemproxy
pipe = self._client.pipeline(transaction=False)
for key, value in _items(mapping):
dump = self.dump_object(value)
if timeout == -1:
pipe.set(name=self.key_prefix + key, value=dump)
else:
pipe.setex(name=self.key_prefix + key, value=dump,
time=timeout)
return pipe.execute()
def delete(self, key):
return self._client.delete(self.key_prefix + key)
def delete_many(self, *keys):
if not keys:
return
if self.key_prefix:
keys = [self.key_prefix + key for key in keys]
return self._client.delete(*keys)
def has(self, key):
return self._client.exists(self.key_prefix + key)
def clear(self):
status = False
if self.key_prefix:
keys = self._client.keys(self.key_prefix + '*')
if keys:
status = self._client.delete(*keys)
else:
status = self._client.flushdb()
return status
def inc(self, key, delta=1):
return self._client.incr(name=self.key_prefix + key, amount=delta)
def dec(self, key, delta=1):
return self._client.decr(name=self.key_prefix + key, amount=delta)
