Python Kafka消费者缺少轮询一些消息 [英] Python Kafka consumer missing to poll some messages

问题描述

我的 Kafka 消费者的代码如下

The code for my Kafka consumer looks like this

def read_messages_from_kafka():
    topic = 'my-topic'
    consumer = KafkaConsumer(
        bootstrap_servers=['my-host1', 'my-host2'],
        client_id='my-client',
        group_id='my-group',
        auto_offset_reset='earliest',
        enable_auto_commit=False,
        api_version=(0, 8, 2)
    )
    consumer.assign([TopicPartition(topic, 0), TopicPartition(topic, 1)])

    messages = consumer.poll(timeout_ms=kafka_config.poll_timeout_ms, max_records=kafka_config.poll_max_records)

    for partition in messages.values():
        for message in partition:
            log.info("read {}".format(message))

    if messages:
        consumer.commit()

    next_offset0, next_offset1 = consumer.position(TopicPartition(topic, 0)), consumer.position(TopicPartition(topic, 1))
    log.info("next offset0={} and offset1={}".format(next_offset0, next_offset1))

while True:
    read_messages_from_kafka()
    sleep(kafka_config.poll_sleep_ms / 1000.0)

我意识到这种消费者设置无法读取所有消息.我无法重现此问题，因为它是间歇性问题.

I have realised that this setup of consumer is not able to read all the messages. And I am not able to reproduce this as it's intermittent issue.

当我将使用 kafka-cat 的最后 100 条消息与此消费者进行比较时，我发现我的消费者间歇性地随机错过了几条消息.我的消费者有什么问题?

When I compare last 100 messages using kafka-cat to this consumer, I found that my consumer intermittently misses few messages randomly. What's wrong with my consumer?

kafkacat -C -b my-host1 -X broker.version.fallback=0.8.2.1 -t my-topic -o -100

只有在python中使用消息的方法太多了.应该有一种方法，最好只有一种明显的方法.

There are just too many ways to consume messages in python. There should be one and preferably only one obvious way to do it.

推荐答案

您的 Kafka 客户端存在丢失消息的问题.我在此处找到了解决方案:

There is a problem of missing messages in your Kafka client. I found solution here:

while True:
    raw_messages = consumer.poll(timeout_ms=1000, max_records=5000)
    for topic_partition, messages in raw_messages.items():
        application_message = json.loads(message.value.decode())

还有另外一个 Kafka 客户端存在:confluent_kafka.它没有这样的问题.

Also there is another Kafka client exists: confluent_kafka. It has no such problem.

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