56 lines
1.7 KiB
Python
56 lines
1.7 KiB
Python
|
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
|
||
|
)
|