Question

我想通过KafkaUtils.createDirectStream从任意偏移消耗kafka消息。

我的源代码：

import sys

from pyspark import SparkContext
from pyspark.streaming import StreamingContext
from pyspark.streaming.kafka import KafkaUtils, TopicAndPartition

def functionToCreateContext():
    sc = SparkContext(appName="PythonStreamingDirectKafkaWordCount")
    ssc = StreamingContext(sc, 2)
    kvs = KafkaUtils.createDirectStream(
        ssc,
        ['test123'],
        {"metadata.broker.list": "localhost:9092"},
        {TopicAndPartition("test123", 0): 100, TopicAndPartition("test123", 1): 100}
    )
    #kvs = kvs.checkpoint(10)
    lines = kvs.map(lambda x: x[1])
    counts = lines.flatMap(lambda line: line.split(" ")) \
        .map(lambda word: (word, 1)) \
        .reduceByKey(lambda a, b: a+b)
    counts.pprint()
    return ssc

if __name__ == "__main__":
    ssc = StreamingContext.getOrCreate("./checkpoint", functionToCreateContext())

    ssc.start()
    ssc.awaitTermination()

但是得到如下错误：

Traceback (most recent call last):
  File "/usr/local/spark-1.6.0-bin-hadoop2.6/examples/src/main/python/streaming/direct_kafka_wordcount.py", line 56, in <module>
    ssc = StreamingContext.getOrCreate("./checkpoint", functionToCreateContext())
  File "/usr/local/spark-1.6.0-bin-hadoop2.6/examples/src/main/python/streaming/direct_kafka_wordcount.py", line 45, in functionToCreateContext
    {TopicAndPartition("test123", 0): 100, TopicAndPartition("test123", 1): 100}
TypeError: unhashable type: 'TopicAndPartition'

pyspark源代码：

@staticmethod
def createDirectStream(ssc, topics, kafkaParams, fromOffsets=None,
                       keyDecoder=utf8_decoder, valueDecoder=utf8_decoder,
                       messageHandler=None):

class TopicAndPartition(object):
    """
    Represents a specific top and partition for Kafka.
    """

    def __init__(self, topic, partition):
        """
        Create a Python TopicAndPartition to map to the Java related object
        :param topic: Kafka topic name.
        :param partition: Kafka partition id.
        """
        self._topic = topic
        self._partition = partition

    def _jTopicAndPartition(self, helper):
        return helper.createTopicAndPartition(self._topic, self._partition)
    .........

jfromOffsets = dict([(k._jTopicAndPartition(helper),
                      v) for (k, v) in fromOffsets.items()])

fromOffsets应该是一个dict，dict的键应该是TopicAndPartition个对象。

对此有何想法？

Answer 1

pyspark有python3的错误，TopicAndPartition类缺少hash方法，因此你应该将python3改为python2，错误就消失了。

然后应该将偏移量从int转换为long：

{TopicAndPartition("test123", 0): long(100), TopicAndPartition("test123", 1): long(100)}

TypeError的原因是什么：不可用类型：＆＃39; TopicAndPartition＆＃39;什么时候KafkaUtils.createDirectStream？

1 个答案: