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import math |
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import sys |
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from bisect import bisect |
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5
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if sys.version_info >= (2, 5): |
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import hashlib |
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md5_constructor = hashlib.md5 |
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else: |
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import md5 |
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md5_constructor = md5.new |
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11
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12
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13
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class HashRing(object): |
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def __init__(self, nodes=None, weights=None): |
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"""`nodes` is a list of objects that have a proper __str__ representation. |
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`weights` is dictionary that sets weights to the nodes. The default |
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weight is that all nodes are equal. |
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""" |
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self.ring = dict() |
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self._sorted_keys = [] |
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self.nodes = nodes |
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if not weights: |
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weights = {} |
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self.weights = weights |
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self._generate_circle() |
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def _generate_circle(self): |
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"""Generates the circle. |
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""" |
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total_weight = 0 |
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for node in self.nodes: |
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total_weight += self.weights.get(node, 1) |
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for node in self.nodes: |
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weight = 1 |
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40
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if node in self.weights: |
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weight = self.weights.get(node) |
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factor = math.floor((40 * len(self.nodes) * weight) / total_weight) |
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for j in range(0, int(factor)): |
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b_key = self._hash_digest('%s-%s' % (node, j)) |
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48
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for i in range(0, 3): |
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key = self._hash_val(b_key, lambda x: x + i * 4) |
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50
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self.ring[key] = node |
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self._sorted_keys.append(key) |
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self._sorted_keys.sort() |
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54
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55
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def get_node(self, string_key): |
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"""Given a string key a corresponding node in the hash ring is returned. |
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58
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If the hash ring is empty, `None` is returned. |
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""" |
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pos = self.get_node_pos(string_key) |
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if pos is None: |
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return None |
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return self.ring[self._sorted_keys[pos]] |
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def get_node_pos(self, string_key): |
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"""Given a string key a corresponding node in the hash ring is returned |
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along with it's position in the ring. |
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69
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If the hash ring is empty, (`None`, `None`) is returned. |
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""" |
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if not self.ring: |
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return None |
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74
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key = self.gen_key(string_key) |
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76
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nodes = self._sorted_keys |
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pos = bisect(nodes, key) |
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if pos == len(nodes): |
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return 0 |
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else: |
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return pos |
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84
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def iterate_nodes(self, string_key, distinct=True): |
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"""Given a string key it returns the nodes as a generator that can hold the key. |
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87
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The generator iterates one time through the ring |
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starting at the correct position. |
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90
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if `distinct` is set, then the nodes returned will be unique, |
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i.e. no virtual copies will be returned. |
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""" |
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if not self.ring: |
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yield None, None |
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95
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96
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returned_values = set() |
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97
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98
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def distinct_filter(value): |
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if str(value) not in returned_values: |
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returned_values.add(str(value)) |
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return value |
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102
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103
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pos = self.get_node_pos(string_key) |
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for key in self._sorted_keys[pos:]: |
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val = distinct_filter(self.ring[key]) |
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if val: |
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yield val |
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108
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109
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for i, key in enumerate(self._sorted_keys): |
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if i < pos: |
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val = distinct_filter(self.ring[key]) |
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112
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if val: |
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yield val |
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115
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def gen_key(self, key): |
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"""Given a string key it returns a long value, |
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this long value represents a place on the hash ring. |
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118
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119
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md5 is currently used because it mixes well. |
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120
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""" |
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121
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b_key = self._hash_digest(key) |
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return self._hash_val(b_key, lambda x: x) |
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123
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124
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def _hash_val(self, b_key, entry_fn): |
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return (b_key[entry_fn(3)] << 24) | (b_key[entry_fn(2)] << 16) | ( |
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b_key[entry_fn(1)] << 8) | b_key[entry_fn(0)] |
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127
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128
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def _hash_digest(self, key): |
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129
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m = md5_constructor() |
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130
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key = key.encode() |
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131
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m.update(key) |
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132
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return m.digest() |
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133
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134
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135
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if __name__ == '__main__': |
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136
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from collections import defaultdict |
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137
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servers = [ |
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138
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'192.168.0.246:11212', '192.168.0.247:11212', '192.168.0.248:11212', |
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'192.168.0.249:11212' |
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140
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] |
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141
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142
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ring = HashRing(servers) |
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143
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keys = ['{}'.format(i) for i in range(100)] |
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144
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mapped = defaultdict(list) |
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145
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for k in keys: |
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server = ring.get_node(k) |
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mapped[server].append(k) |
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148
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149
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for k, v in mapped.items(): |
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150
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print(k, v) |
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151
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milvus-io /
milvus
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