def test_full_jitter(self, values):
jittered = list(full_jitter(values))
self.assertThat(jittered, AllMatch(IsInstance(float)))
self.assertThat(
jittered,
AllMatch(MatchesAll(GreaterThanOrEqual(0.0), LessThan(10000.0))),
)
def gen_retry_intervals(base=0.01, rate=2.5, maximum=10.0):
"""Generate retry intervals based on an exponential series.
Once any interval exceeds `maximum` the interval generated will forever be
`maximum`; this effectively disconnects from the exponential series. All
intervals will be subject to "jitter" as a final step.
The defaults seem like reasonable coefficients for a capped, full-jitter,
exponential back-off series, and were derived by experimentation at the
command-line. Real-world experience may teach us better values.
"""
# An exponentially growing series...
intervals = exponential_growth(base, rate)
# from which we stop pulling one we've hit a maximum...
intervals = takewhile((lambda i: i < maximum), intervals)
# and thereafter return the maximum value indefinitely...
intervals = chain(intervals, repeat(maximum))
# and to which we add some randomness.
return full_jitter(intervals)