47 lines
1.2 KiB
Python
47 lines
1.2 KiB
Python
from pymemcache.client.murmur3 import murmur3_32
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class RendezvousHash:
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"""
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Implements the Highest Random Weight (HRW) hashing algorithm most
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commonly referred to as rendezvous hashing.
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Originally developed as part of python-clandestined.
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Copyright (c) 2014 Ernest W. Durbin III
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"""
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def __init__(self, nodes=None, seed=0, hash_function=murmur3_32):
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"""
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Constructor.
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"""
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self.nodes = []
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self.seed = seed
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if nodes is not None:
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self.nodes = nodes
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self.hash_function = lambda x: hash_function(x, seed)
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def add_node(self, node):
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if node not in self.nodes:
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self.nodes.append(node)
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def remove_node(self, node):
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if node in self.nodes:
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self.nodes.remove(node)
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else:
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raise ValueError("No such node %s to remove" % (node))
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def get_node(self, key):
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high_score = -1
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winner = None
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for node in self.nodes:
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score = self.hash_function(f"{node}-{key}")
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if score > high_score:
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(high_score, winner) = (score, node)
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elif score == high_score:
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(high_score, winner) = (score, max(str(node), str(winner)))
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return winner
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