def eval(self, redis: StrictRedis, *keys, **kwargs):
"""Tries to call ``EVALSHA`` with the `hash` and then, if it fails, calls
regular ``EVAL`` with.
"""
args = kwargs.pop('args', ())
# make sure number of keys passed matches keys required
if len(keys) != self._num_keys:
raise RedisScriptError(
f"Key length mismatch. Expected {self._num_keys}. "
f"Got {len(keys)} in {self._name}")
if kwargs:
raise TypeError(
f"Unexpected keyword arguments {kwargs.keys()} in {self._name}."
)
try:
return redis.evalsha(self._script_digest, self._num_keys,
*keys + args)
except NoScriptError:
return redis.eval(self._script_encoded, self._num_keys,
*keys + args)
class Cache:
def __init__(self):
self.configured = False
self.host = None
self.port = None
self.password = None
self.prefix = None
self._client = None
def _connect(self):
self._client = StrictRedis(self.host,
port=self.port,
password=self.password)
def connect(self, host, port=6379, password=None, prefix=None):
"""
Only support db 0
"""
self.configured = True
self.host = host
self.port = port
self.password = password
self.prefix = prefix
if self.prefix is None:
raise Exception('Prefix should provided')
self._connect()
def __getattribute__(self, attr, *args, **kwargs):
try:
return super().__getattribute__(attr)
except AttributeError:
if not self._client:
raise Exception('Cache client not initialized')
return getattr(self._session, attr)
def make_key(self, key):
return f'{self.prefix}:cache:{key}'
@staticmethod
def encode(value):
if isinstance(value, bool) or not isinstance(value, int):
return pickle.dumps(value)
return value
@staticmethod
def decode(value):
try:
value = int(value)
except (ValueError, TypeError):
value = pickle.loads(value)
return value
def set(self, key, value, timeout=DEFAULT_TIMEOUT):
key = self.make_key(key)
value = self.encode(value)
return bool(self._client.set(key, value, ex=timeout))
def get(self, key):
key = self.make_key(key)
value = self._client.get(key)
if value is None:
return value
return self.decode(value)
def _incr(self, key, delta=1):
"""Always check key exists
"""
# if key expired after exists check, then we get
# key with wrong value and ttl -1.
# use lua script for atomicity
lua = """
local exists = redis.call('EXISTS', KEYS[1])
if (exists == 1) then
return redis.call('INCRBY', KEYS[1], ARGV[1])
else return false end
"""
value = self._client.eval(lua, 1, key, delta)
if value is None:
raise ValueError("Key '%s' not found" % key)
return value
def incr(self, key, delta=1):
key = self.make_key(key)
return self._incr(key, delta=delta)
def decr(self, key, delta=1):
key = self.make_key(key)
return self._incr(key, delta=-delta)
