from __future__ import absolute_import
from kafka.vendor import six
from .base import Partitioner
[docs]class Murmur2Partitioner(Partitioner):
"""
Implements a partitioner which selects the target partition based on
the hash of the key. Attempts to apply the same hashing
function as mainline java client.
"""
[docs] def partition(self, key, partitions=None):
if not partitions:
partitions = self.partitions
# https://github.com/apache/kafka/blob/0.8.2/clients/src/main/java/org/apache/kafka/clients/producer/internals/Partitioner.java#L69
idx = (murmur2(key) & 0x7fffffff) % len(partitions)
return partitions[idx]
[docs]class LegacyPartitioner(Partitioner):
"""DEPRECATED -- See Issue 374
Implements a partitioner which selects the target partition based on
the hash of the key
"""
[docs] def partition(self, key, partitions=None):
if not partitions:
partitions = self.partitions
size = len(partitions)
idx = hash(key) % size
return partitions[idx]
# Default will change to Murmur2 in 0.10 release
HashedPartitioner = LegacyPartitioner
# https://github.com/apache/kafka/blob/0.8.2/clients/src/main/java/org/apache/kafka/common/utils/Utils.java#L244
[docs]def murmur2(key):
"""Pure-python Murmur2 implementation.
Based on java client, see org.apache.kafka.common.utils.Utils.murmur2
Args:
key: if not a bytes type, encoded using default encoding
Returns: MurmurHash2 of key bytearray
"""
# Convert key to bytes or bytearray
if isinstance(key, bytearray) or (six.PY3 and isinstance(key, bytes)):
data = key
else:
data = bytearray(str(key).encode())
length = len(data)
seed = 0x9747b28c
# 'm' and 'r' are mixing constants generated offline.
# They're not really 'magic', they just happen to work well.
m = 0x5bd1e995
r = 24
# Initialize the hash to a random value
h = seed ^ length
length4 = length // 4
for i in range(length4):
i4 = i * 4
k = ((data[i4 + 0] & 0xff) +
((data[i4 + 1] & 0xff) << 8) +
((data[i4 + 2] & 0xff) << 16) +
((data[i4 + 3] & 0xff) << 24))
k &= 0xffffffff
k *= m
k &= 0xffffffff
k ^= (k % 0x100000000) >> r # k ^= k >>> r
k &= 0xffffffff
k *= m
k &= 0xffffffff
h *= m
h &= 0xffffffff
h ^= k
h &= 0xffffffff
# Handle the last few bytes of the input array
extra_bytes = length % 4
if extra_bytes >= 3:
h ^= (data[(length & ~3) + 2] & 0xff) << 16
h &= 0xffffffff
if extra_bytes >= 2:
h ^= (data[(length & ~3) + 1] & 0xff) << 8
h &= 0xffffffff
if extra_bytes >= 1:
h ^= (data[length & ~3] & 0xff)
h &= 0xffffffff
h *= m
h &= 0xffffffff
h ^= (h % 0x100000000) >> 13 # h >>> 13;
h &= 0xffffffff
h *= m
h &= 0xffffffff
h ^= (h % 0x100000000) >> 15 # h >>> 15;
h &= 0xffffffff
return h