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BackoffTimer.py
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BackoffTimer.py
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from decimal import Decimal
def _Decimal(v):
if not isinstance(v, Decimal):
return Decimal(str(v))
return v
class BackoffTimer(object):
"""
This is a timer that is smart about backing off exponentially when there are problems
"""
def __init__(self, min_interval, max_interval, ratio=.25, short_length=10, long_length=250):
assert isinstance(min_interval, (int, float, Decimal))
assert isinstance(max_interval, (int, float, Decimal))
self.min_interval = _Decimal(min_interval)
self.max_interval = _Decimal(max_interval)
self.max_short_timer = (self.max_interval - self.min_interval) * _Decimal(ratio)
self.max_long_timer = (self.max_interval - self.min_interval) * (1 - _Decimal(ratio))
self.short_unit = self.max_short_timer / _Decimal(short_length)
self.long_unit = self.max_long_timer / _Decimal(long_length)
self.short_interval = Decimal(0)
self.long_interval = Decimal(0)
def success(self):
"""Update the timer to reflect a successfull call"""
self.short_interval -= self.short_unit
self.long_interval -= self.long_unit
self.short_interval = max(self.short_interval, Decimal(0))
self.long_interval = max(self.long_interval, Decimal(0))
def failure(self):
"""Update the timer to reflect a failed call"""
self.short_interval += self.short_unit
self.long_interval += self.long_unit
self.short_interval = min(self.short_interval, self.max_short_timer)
self.long_interval = min(self.long_interval, self.max_long_timer)
def get_interval(self):
return float(self.min_interval + self.short_interval + self.long_interval)