70 lines
2.1 KiB
Python
70 lines
2.1 KiB
Python
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import collections
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import math
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import time
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class RateMeter:
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def __init__(self, span):
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'''
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This class is used to calculate a rolling average of
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units per second over `span` seconds.
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Minimum span is 1 second.
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Set `span` to None to calculate unit/s over the lifetime of the object
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after the first digest, rather than over a span.
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This saves the effort of tracking timestamps. Don't just use a large number!
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'''
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if span is not None and span < 1:
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raise ValueError('Span must be >= 1')
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self.sum = 0
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self.span = span
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self.tracking = collections.deque()
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self.first_digest = None
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def digest(self, value):
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now = math.ceil(time.time())
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self.sum += value
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if self.span is None:
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if self.first_digest is None:
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self.first_digest = now
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return
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earlier = now - self.span
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while len(self.tracking) > 0 and self.tracking[0][0] < earlier:
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(timestamp, pop_value) = self.tracking.popleft()
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self.sum -= pop_value
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if len(self.tracking) == 0 or self.tracking[-1] != now:
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self.tracking.append([now, value])
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else:
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self.tracking[-1][1] += value
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def report(self):
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'''
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Return a tuple containing the running sum, the time span
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over which the rate is being calculated, and the rate in
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units per second.
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(sum, time_interval, rate)
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'''
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# Flush the old values, ensure self.first_digest exists.
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self.digest(0)
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if self.span is None:
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now = math.ceil(time.time())
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time_interval = now - self.first_digest
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else:
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# No risk of IndexError because the digest(0) ensures we have
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# at least one entry.
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time_interval = self.tracking[-1][0] - self.tracking[0][0]
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if time_interval == 0:
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return (self.sum, 0, self.sum)
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rate = self.sum / time_interval
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time_interval = round(time_interval, 3)
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rate = round(rate, 3)
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return (self.sum, time_interval, rate)
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