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python3
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botocore
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retries
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Filename :
throttling.py
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from collections import namedtuple CubicParams = namedtuple('CubicParams', ['w_max', 'k', 'last_fail']) class CubicCalculator: _SCALE_CONSTANT = 0.4 _BETA = 0.7 def __init__( self, starting_max_rate, start_time, scale_constant=_SCALE_CONSTANT, beta=_BETA, ): self._w_max = starting_max_rate self._scale_constant = scale_constant self._beta = beta self._k = self._calculate_zero_point() self._last_fail = start_time def _calculate_zero_point(self): scaled_value = (self._w_max * (1 - self._beta)) / self._scale_constant k = scaled_value ** (1 / 3.0) return k def success_received(self, timestamp): dt = timestamp - self._last_fail new_rate = self._scale_constant * (dt - self._k) ** 3 + self._w_max return new_rate def error_received(self, current_rate, timestamp): # Consider not having this be the current measured rate. # We have a new max rate, which is the current rate we were sending # at when we received an error response. self._w_max = current_rate self._k = self._calculate_zero_point() self._last_fail = timestamp return current_rate * self._beta def get_params_snapshot(self): """Return a read-only object of the current cubic parameters. These parameters are intended to be used for debug/troubleshooting purposes. These object is a read-only snapshot and cannot be used to modify the behavior of the CUBIC calculations. New parameters may be added to this object in the future. """ return CubicParams( w_max=self._w_max, k=self._k, last_fail=self._last_fail )