class MemcachedAdapter(BaseAdapter):
"""
Exposes a cache store using Memcached.
Exposes `pymemcache`'s exceptions.
"""
def __init__(self, host='localhost', port=11211, **kwargs):
super().__init__()
self.store = Client((host, port), **kwargs)
def set(self, key, value, ttl):
if ttl == -1:
ttl = 0
return self.store.set(key, value, expire=ttl)
def batch_set(self, keys, values, ttls):
# There's two reasons to recode pymemcache.set_multi():
# - It returns a list of keys that failed to be inserted, and the base expects a boolean
# - It only allows a unique ttl for all keys
commands = []
ttls = [0 if ttl == -1 else ttl for ttl in ttls]
for key, value, ttl in zip(keys, values, ttls):
ttl = self.store._check_integer(ttl, 'expire') # pylint: disable=protected-access
key = self.store.check_key(key)
value, flags = self.store.serde.serialize(key, value)
command = b'set ' + key
command += b' ' + str(flags).encode(self.store.encoding)
command += b' ' + ttl
command += b' ' + str(len(value)).encode(
self.store.encoding) + b'\r\n'
command += value.encode(self.store.encoding) + b'\r\n'
commands.append(command)
results = self.store._misc_cmd(commands, 'set', False) # pylint: disable=protected-access
for line in results:
if line == b'NOT_STORED':
return False
return True
def get(self, key):
value = self.store.get(key)
return value
def batch_get(self, keys):
key_to_value = self.store.get_multi(keys)
values = [
key_to_value[key] if key in key_to_value else None for key in keys
]
return values
def delete(self, key):
return self.store.delete(key, noreply=False)
def batch_delete(self, keys):
# Here as well, pymemcache.delete_multi() always returns True
commands = []
for key in keys:
key = self.store.check_key(key)
command = b'delete ' + key + b'\r\n'
commands.append(command)
results = self.store._misc_cmd(commands, 'delete', False) # pylint: disable=protected-access
for line in results:
print(f"\"{line}\"")
if line == b'NOT_FOUND':
return False
return True
def exists(self, key):
# Can't just cast to bool since we can store falsey values
return self.store.get(key) is not None
def flush(self):
return self.store.flush_all(noreply=False)
def ping(self):
return bool(self.store.stats())
@property
def connection_exceptions(self):
return (MemcacheUnexpectedCloseError, MemcacheServerError,
MemcacheUnknownError)
