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51
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1 # Write a function taht maps
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2 # Key string to one of N servers
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3 from bisect import bisect_left
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4 from hashlib import sha256
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5
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6 class Server:
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7
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8 def __init__(self):
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9 self.id = str(sha256())
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10
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11 class ConsistentHash:
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12 def __init__(self):
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13 self.server = []
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14 self.hash_key_to_server = {}
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15 self.hash_range = 10000
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16
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17 def get_hash_pos(self, key: str) -> int:
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18 x = sha256(bytes(key, "utf-8"))
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19 return int.from_bytes(x.digest()[:8]) % self.hash_range
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20
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21 def add_server(self, server: Server):
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22 self.server.append(server)
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23 for i in range(len(self.server) + 1):
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24 hash_key = self.get_hash_pos(server.id)
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25 self.hash_key_to_server[hash_key] = i
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26
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27 def get_server(self, key):
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28 hash_key = self.get_hash_pos(key)
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29 return self.server[bisect_left(list(self.hash_key_to_server.keys()), hash_key)]
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30
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31 def remove_server(self, server):
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32 hash_key = self.get_hash_pos(server.id)
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