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# -*- coding: utf-8 -*-
"""This test is vastly inspired by Mike Bayer's article:
http://techspot.zzzeek.org/2012/07/07/the-absolutely-simplest-consistent-hashing-example/
"""
from collections import Counter
from math import sqrt
from random import randint
from uhashring import HashRing
def _pop_std_dev(population):
mean = sum(population) / len(population)
return sqrt(sum(pow(n - mean, 2) for n in population) / len(population))
def test_distribution():
ring = HashRing()
numnodes = 10
numhits = 1000
numvalues = 10000
for i in range(1, numnodes + 1):
ring["node{}".format(i)] = {"instance": "node_value{}".format(i)}
distribution = Counter()
for i in range(numhits):
key = str(randint(1, numvalues))
node = ring[key]
distribution[node] += 1
# count of hits matches what is observed
assert sum(distribution.values()) == numhits
# usually under 20
standard_dev = _pop_std_dev(distribution.values())
assert standard_dev <= 20
# all nodes should be used
assert len(distribution) == numnodes
# just to test getting keys, see that we got the values
# back and not keys or indexes or whatever.
assert set(distribution.keys()) == set(
"node_value{}".format(i) for i in range(1, 1 + numnodes)
)
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