# Original work Copyright 2013 Arnaud Porterie
# Modified work Copyright 2016 Frazer McLean
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import collections
import functools
import sys
import threading
import time
try:
import asyncio
except ImportError:
asyncio = None
__author__ = "Frazer McLean <frazer@frazermclean.co.uk>"
__version__ = "1.2.0.post0"
__license__ = "Apache"
__description__ = "Simple python rate limiting object"
PY35 = sys.version_info >= (3, 5)
[docs]
class RateLimiter(object):
"""Provides rate limiting for an operation with a configurable number of
requests for a time period.
"""
def __init__(self, max_calls, period=1.0, callback=None):
"""Initialize a RateLimiter object which enforces as much as max_calls
operations on period (eventually floating) number of seconds.
"""
if period <= 0:
raise ValueError("Rate limiting period should be > 0")
if max_calls <= 0:
raise ValueError("Rate limiting number of calls should be > 0")
# We're using a deque to store the last execution timestamps, not for
# its maxlen attribute, but to allow constant time front removal.
self.calls = collections.deque()
self.period = period
self.max_calls = max_calls
self.callback = callback
self._lock = threading.Lock()
self._alock = None
# Lock to protect creation of self._alock
self._init_lock = threading.Lock()
[docs]
def _init_async_lock(self):
with self._init_lock:
if self._alock is None:
self._alock = asyncio.Lock()
def __call__(self, f):
"""The __call__ function allows the RateLimiter object to be used as a
regular function decorator.
"""
@functools.wraps(f)
def wrapped(*args, **kwargs):
with self:
return f(*args, **kwargs)
return wrapped
def __enter__(self):
with self._lock:
# We want to ensure that no more than max_calls were run in the allowed
# period. For this, we store the last timestamps of each call and run
# the rate verification upon each __enter__ call.
if len(self.calls) >= self.max_calls:
until = time.time() + self.period - self._timespan
if self.callback:
t = threading.Thread(target=self.callback, args=(until,))
t.daemon = True
t.start()
sleeptime = until - time.time()
if sleeptime > 0:
time.sleep(sleeptime)
return self
def __exit__(self, exc_type, exc_val, exc_tb):
with self._lock:
# Store the last operation timestamp.
self.calls.append(time.time())
# Pop the timestamp list front (ie: the older calls) until the sum goes
# back below the period. This is our 'sliding period' window.
while self._timespan >= self.period:
self.calls.popleft()
# if PY35:
# # We have to exec this due to syntax errors on earlier versions.
# aenter_code = dedent("""
# async def __aenter__(self):
# if self._alock is None:
# self._init_async_lock()
#
# with await self._alock:
# # We want to ensure that no more than max_calls were run in the allowed
# # period. For this, we store the last timestamps of each call and run
# # the rate verification upon each __enter__ call.
# if len(self.calls) >= self.max_calls:
# until = time.time() + self.period - self._timespan
# if self.callback:
# asyncio.ensure_future(self.callback(until))
# sleeptime = until - time.time()
# if sleeptime > 0:
# await asyncio.sleep(sleeptime)
# return self
#
# """)
# exec(aenter_code)
#
# # __aexit__ = asyncio.coroutine(__exit__)
# async def __aexit__(self, exc_type, exc_val, exc_tb):
# self.__exit__(exc_type, exc_val, exc_tb)
@property
def _timespan(self):
return self.calls[-1] - self.calls[0]