cli tool for counting occurence rate of lines with certain keyword with ewma algorithm.

ewma.py

#!/usr/bin/env python
'''
count occurence rate of lines with certain keyword with ewma algorithm.
'''

import math
import time
import sys


milli_second = 1000000
second = 1000 * milli_second
minute = 60 * second

interval = 5 * second
seconds_per_minute = 60.0
one_minute = 1
five_minutes = 5
fifteen_minutes = 15
interval_ = 1.0 * interval
m1_alpha = 1 - math.exp(-5.0 / (seconds_per_minute * one_minute))
m5_alpha = 1 - math.exp(-5.0 / (seconds_per_minute * five_minutes))
m15_alpha = 1 - math.exp(-5.0 / (seconds_per_minute * fifteen_minutes))


class EWMA:
    def __init__(self, alpha):
        self.alpha = alpha
        self.uncounted = 0
        self.initialized = False
        self.rate = 0.0

    def update(self, n):
        self.uncounted += n

    def tick(self):
        count = self.uncounted
        self.uncounted = 0
        instant_rate = (count*1.0) / interval
        if self.initialized:
            self.rate += (self.alpha * (instant_rate - self.rate))
        else:
            self.rate = instant_rate
            self.initialized = True

    def get_rate(self, unit):
        return self.rate * unit


class Meter:
    def __init__(self):
        self.m1 = EWMA(m1_alpha)
        self.m5 = EWMA(m5_alpha)
        self.m15 = EWMA(m15_alpha)
        self.count = 0
        self.start = now()
        self.last_tick = self.start

    def tick_if_necessary(self):
        current = now()
        age = current - self.last_tick
        if age >= interval:
            self.last_tick = current - (age % interval)
            for i in range(0, age / interval):
                self.m1.tick()
                self.m5.tick()
                self.m15.tick()

    def mark(self, n=1):
        self.tick_if_necessary()
        self.count += n
        self.m1.update(n)
        self.m5.update(n)
        self.m15.update(n)

    def get_mean_rate(self, unit=second):
        if self.count == 0:
            return 0.0
        else:
            return ((self.count * 1.0) / (now() - self.start)) * unit

    def get_m1_rate(self):
        self.tick_if_necessary()
        return self.m1.get_rate(second)

    def get_m5_rate(self):
        self.tick_if_necessary()
        return self.m5.get_rate(second)

    def get_m15_rate(self):
        self.tick_if_necessary()
        return self.m15.get_rate(second)


def now():
    return int(time.time() * second)


if __name__ == '__main__':
    keyword = sys.argv[1]
    meter = Meter()
    start = time.time()
    while True:
        line = sys.stdin.readline()
        if keyword in line:
            meter.mark()
        now_ = time.time()
        if now_ - start > 1:
            start = now_
            print("\n\n%s" % time.ctime())
            print("count\t=\t%s" % meter.count)
            print("mean rate \t=\t%s" % meter.get_mean_rate())
            print("1 minute rate \t=\t%s" % meter.get_m1_rate())
            print("5 minutes rate \t=\t%s" % meter.get_m5_rate())
            print("15 minutes rate \t=\t%s" % meter.get_m15_rate())