kafka python如何使用json消息

iqxoj9l9 于 2021-06-06 发布在 Kafka

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我是一个相当新的python和Kafka开始。我需要发送和使用json消息。为此，我使用kafka python与kafka进行通信。


# Producer.py

from kafka import KafkaProducer
import json
producer = KafkaProducer(bootstrap_servers='localhost:9092',value_serializer=lambda v: json.dumps(v).encode('utf-8'))
producer.send('offering_new', {"dataObjectID": "test1"})

# Consumer.py

import json
from kafka import KafkaConsumer
consumer = KafkaConsumer(bootstrap_servers='localhost:9092',auto_offset_reset='earliest', value_deserializer=lambda m: json.loads(m.decode('utf-8')))
consumer.subscribe(['offering_new'])
for message in consumer :
    print(message)

不过，我得到了消费者的以下例外情况：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/paras/.local/lib/python3.6/site-packages/kafka/consumer/group.py", line 1111, in __next__
    return next(self._iterator)
  File "/home/paras/.local/lib/python3.6/site-packages/kafka/consumer/group.py", line 1082, in _message_generator
    for msg in self._fetcher:
  File "/home/paras/.local/lib/python3.6/site-packages/kafka/consumer/fetcher.py", line 482, in __next__
    return next(self._iterator)
  File "/home/paras/.local/lib/python3.6/site-packages/kafka/consumer/fetcher.py", line 388, in _message_generator
    self._next_partition_records = self._parse_fetched_data(completion)
  File "/home/paras/.local/lib/python3.6/site-packages/kafka/consumer/fetcher.py", line 799, in _parse_fetched_data
    unpacked = list(self._unpack_message_set(tp, records))
  File "/home/paras/.local/lib/python3.6/site-packages/kafka/consumer/fetcher.py", line 458, in _unpack_message_set
    tp.topic, record.value)
  File "/home/paras/.local/lib/python3.6/site-packages/kafka/consumer/fetcher.py", line 492, in _deserialize
    return f(bytes_)
  File "<stdin>", line 1, in <lambda>
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

我正在pythonshell中运行上述代码。有人能告诉我哪里出了问题吗？

python apache-kafka python-3.x kafka-python

来源：https://stackoverflow.com/questions/55534547/kafka-python-how-to-consume-json-message

2条答案

按热度按时间

w7t8yxp51#

与 auto_offset_reset='earliest' 您已将使用者配置为读取主题中的所有消息。json解码错误表明，以前生成给主题的某些消息实际上不是json格式。
一些解决方案：
（1）从主题的尾部开始消费： auto_offset_reset='latest' （2）开始新主题： consumer.subscribe(['offering_new_too']) （3）使用更全面的反序列化程序：

def forgiving_json_deserializer(v):
    return if v is None
    try:
        return json.loads(v.decode('utf-8'))
    except json.decoder.JSONDecodeError:
        log.exception('Unable to decode: %s', v)
        return None

KafkaConsumer(value_deserializer=forgiving_json_deserializer, ...)

希望这有帮助！

赞(0）回复(0）举报 2021-06-06

8mmmxcuj2#

确保你有以下流程

pip install kafka-python

在python脚本中导入lib下方

from kafka import KafkaConsumer
from json import loads

创建kafka消费对象，如下所示

consumer = KafkaConsumer(
    'spring_test',
     bootstrap_servers=['localhost:9092'],
     auto_offset_reset='earliest',
     enable_auto_commit=True,
     group_id='my-group',
     value_deserializer=lambda x: loads(x.decode('utf-8')));

打印所有邮件

for message in consumer:
    message = message.value;
    print('{}'.format(message))

希望这也能有所帮助

赞(0）回复(0）举报 2021-06-06

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kafka python如何使用json消息

2条答案

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