Warning: This document is for the development version of Dramatiq.

Source code for dramatiq.rate_limits.rate_limiter

# This file is a part of Dramatiq.
#
# Copyright (C) 2017,2018 CLEARTYPE SRL <bogdan@cleartype.io>
#
# 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.
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# 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/>.

from contextlib import contextmanager

from ..errors import RateLimitExceeded


[docs]class RateLimiter: """ABC for rate limiters. Examples: >>> from dramatiq.rate_limits.backends import RedisBackend >>> backend = RedisBackend() >>> limiter = ConcurrentRateLimiter(backend, "distributed-mutex", limit=1) >>> with limiter.acquire(raise_on_failure=False) as acquired: ... if not acquired: ... print("Mutex not acquired.") ... return ... ... print("Mutex acquired.") Parameters: backend(RateLimiterBackend): The rate limiting backend to use. key(str): The key to rate limit on. """ def __init__(self, backend, key): self.backend = backend self.key = key def _acquire(self): # pragma: no cover raise NotImplementedError def _release(self): # pragma: no cover raise NotImplementedError
[docs] @contextmanager def acquire(self, *, raise_on_failure=True): """Attempt to acquire a slot under this rate limiter. Parameters: raise_on_failure(bool): Whether or not failures should raise an exception. If this is false, the context manager will instead return a boolean value representing whether or not the rate limit slot was acquired. Returns: bool: Whether or not the slot could be acquired. """ acquired = False try: acquired = self._acquire() if raise_on_failure and not acquired: raise RateLimitExceeded("rate limit exceeded for key %(key)r" % vars(self)) yield acquired finally: if acquired: self._release()