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Merge pull request #38 from avatao-content/rate_limit_magic
Rate limit magic
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commit
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# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
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# All Rights Reserved. See LICENSE file for details.
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from functools import wraps
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from functools import wraps, partial
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from time import time, sleep
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from tfw.decorators.lazy_property import lazy_property
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class RateLimiter:
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"""
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Decorator class for rate limiting, blocking.
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When applied to a function this decorator will apply rate limiting
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if the function is invoked more frequently than rate_per_seconds.
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By default rate limiting means sleeping until the next invocation time
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as per __init__ parameter rate_per_seconds.
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Note that this decorator BLOCKS THE THREAD it is being executed on,
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so it is only acceptable for stuff running on a separate thread.
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If this is no good for you please refer to AsyncRateLimiter in this module,
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which is designed not to block and use the IOLoop it is being called from.
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"""
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def __init__(self, rate_per_second):
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"""
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:param rate_per_second: max frequency the decorated method should be
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invoked with
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"""
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self.min_interval = 1 / float(rate_per_second)
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self.fun = None
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self.last_call = time()
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def action(self, seconds_to_next_call):
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if seconds_to_next_call:
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sleep(seconds_to_next_call)
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self.fun()
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def __call__(self, fun):
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@wraps(fun)
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def wrapper(*args, **kwargs):
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self._limit_rate()
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fun(*args, **kwargs)
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self.fun = partial(fun, *args, **kwargs)
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limit_seconds = self._limit_rate()
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self.action(limit_seconds)
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return wrapper
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def _limit_rate(self):
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since_last_call = time() - self.last_call
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to_next_call = self.min_interval - since_last_call
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seconds_since_last_call = time() - self.last_call
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seconds_to_next_call = self.min_interval - seconds_since_last_call
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if seconds_to_next_call > 0:
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return seconds_to_next_call
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self.last_call = time()
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if to_next_call > 0:
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sleep(to_next_call)
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return 0
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class AsyncRateLimiter(RateLimiter):
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"""
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Decorator class for rate limiting, non-blocking.
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The semantics of the rate limiting:
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- unlike RateLimiter this decorator never blocks, instead it adds an async
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callback version of the decorated function to the IOLoop
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(to be executed after the rate limiting has expired).
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- the timing works similarly to RateLimiter
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"""
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def __init__(self, rate_per_second, ioloop_factory):
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"""
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:param rate_per_second: max frequency the decorated method should be
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invoked with
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:param ioloop_factory: callable that should return an instance of the
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IOLoop of the application
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"""
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self._ioloop_factory = ioloop_factory
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self._ioloop = None
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self._last_callback = None
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self._make_action_thread_safe()
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super().__init__(rate_per_second=rate_per_second)
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def _make_action_thread_safe(self):
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self.action = partial(self.ioloop.add_callback, self.action)
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@lazy_property
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def ioloop(self):
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return self._ioloop_factory()
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def action(self, seconds_to_next_call):
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if self._last_callback:
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self.ioloop.remove_timeout(self._last_callback)
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self._last_callback = self.ioloop.call_later(
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seconds_to_next_call,
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self.fun_with_debounce
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)
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def fun_with_debounce(self):
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self.last_call = time()
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self.fun()
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