# This file is a part of Dramatiq.
#
# Copyright (C) 2017,2018 CLEARTYPE SRL <[email protected]>
#
# Dramatiq is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
#
# Dramatiq is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
# License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import redis
from ..backend import RateLimiterBackend
[docs]
class RedisBackend(RateLimiterBackend):
"""A rate limiter backend for Redis_.
Parameters:
client(Redis): An optional client. If this is passed,
then all other parameters are ignored.
url(str): An optional connection URL. If both a URL and
connection parameters are provided, the URL is used.
**parameters: Connection parameters are passed directly
to :class:`redis.Redis`.
.. _redis: https://redis.io
"""
def __init__(self, *, client=None, url=None, **parameters):
if url is not None:
parameters["connection_pool"] = redis.ConnectionPool.from_url(url)
# TODO: Replace usages of StrictRedis (redis-py 2.x) with Redis in Dramatiq 2.0.
self.client = client or redis.StrictRedis(**parameters)
def add(self, key, value, ttl):
return bool(self.client.set(key, value, px=ttl, nx=True))
def incr(self, key, amount, maximum, ttl):
with self.client.pipeline() as pipe:
while True:
try:
pipe.watch(key)
value = int(pipe.get(key) or b"0")
value += amount
if value > maximum:
return False
pipe.multi()
pipe.set(key, value, px=ttl)
pipe.execute()
return True
except redis.WatchError:
continue
def decr(self, key, amount, minimum, ttl):
with self.client.pipeline() as pipe:
while True:
try:
pipe.watch(key)
value = int(pipe.get(key) or b"0")
value -= amount
if value < minimum:
return False
pipe.multi()
pipe.set(key, value, px=ttl)
pipe.execute()
return True
except redis.WatchError:
continue
def incr_and_sum(self, key, keys, amount, maximum, ttl):
with self.client.pipeline() as pipe:
while True:
try:
# TODO: Drop non-callable keys in Dramatiq v2.
key_list = keys() if callable(keys) else keys
pipe.watch(key, *key_list)
value = int(pipe.get(key) or b"0")
value += amount
if value > maximum:
return False
# Fetch keys again to account for net/server latency.
values = pipe.mget(keys() if callable(keys) else keys)
total = amount + sum(int(n) for n in values if n)
if total > maximum:
return False
pipe.multi()
pipe.set(key, value, px=ttl)
pipe.execute()
return True
except redis.WatchError:
continue
def wait(self, key, timeout):
assert timeout is None or timeout >= 1000, "wait timeouts must be >= 1000"
event = self.client.brpoplpush(key, key, (timeout or 0) // 1000)
return event == b"x"
def wait_notify(self, key, ttl):
with self.client.pipeline() as pipe:
pipe.rpush(key, b"x")
pipe.pexpire(key, ttl)
pipe.execute()