python - 从 Kafka 轮询几条消息

Question

我正在使用 confluent_kafka与 Kafka 一起工作的软件包。我以这种方式创建主题:

from confluent_kafka import avro
from confluent_kafka.avro import AvroProducer

def my_producer():
    bootstrap_servers=['my_adress.com:9092',
                    'my_adress.com:9092']

    value_schema = avro.load('/home/ValueSchema.avsc')

    avroProducer = AvroProducer({
        'bootstrap.servers': bootstrap_servers[0]+','+bootstrap_servers[1],
        'schema.registry.url':'http://my_adress.com:8081',
        },
        default_value_schema=value_schema
        )

    for i in range(0, 25000):
        value = {"name":"Yuva","favorite_number":10,"favorite_color":"green","age":i*2}
        avroProducer.produce(topic='my_topik14', value=value)
        avroProducer.flush(0)
    print('Finished!')


if __name__ == '__main__':
    my_producer()

它有效。 (顺便说一下，这会收到 24820 条消息，而不是 25000 条……)我们可以检查一下:

kafka-run-class kafka.tools.GetOffsetShell --broker-list my_adress.com:9092 --topic my_topik14
my_topik14:0:24819

现在我要消费:

from confluent_kafka import KafkaError
from confluent_kafka.avro import AvroConsumer
from confluent_kafka.avro.serializer import SerializerError

bootstrap_servers=['my_adress.com:9092',
                   'my_adress.com:9092']
c = AvroConsumer(
    {'bootstrap.servers': bootstrap_servers[0]+','+bootstrap_servers[1],
     'group.id': 'avroneversleeps',
     'schema.registry.url': 'http://my_adress.com:8081',
     'api.version.request': True,
     'fetch.min.bytes': 100000,
     'consume.callback.max.messages':1000,
     'batch.num.messages':2
     })
c.subscribe(['my_topik14'])
running = True

while running:
    msg = None
    try:
        msg = c.poll(0.1)
        if msg:
            if not msg.error():
                print(msg.value())
                c.commit(msg)
            elif msg.error().code() != KafkaError._PARTITION_EOF:
                print(msg.error())
                running = False
        else:
            print("No Message!! Happily trying again!!")
    except SerializerError as e:
        print("Message deserialization failed for %s: %s" % (msg, e))
        running = False
c.commit()
c.close()

但是有个问题:我只是一条一条地阅读消息。我的问题是如何阅读批量消息？我在 Consumer 配置中尝试了不同的参数，但它们没有任何反应!

---

我还找到了this question在 SO 上并尝试了相同的参数 - 它仍然不起作用。

另请阅读此内容。但这违背了之前的链接...

Answer 1

您可以使用 consume([num_messages=1][, timeout=-1]) 方法来完成。 API 引用这里:

对于消费者: https://docs.confluent.io/current/clients/confluent-kafka-python/index.html#confluent_kafka.Consumer.consume

对于 AvroConsumer: https://docs.confluent.io/current/clients/confluent-kafka-python/index.html?highlight=avroconsumer#confluent_kafka.Consumer.consume

有关此问题的更多信息:

https://github.com/confluentinc/confluent-kafka-python/issues/252