等待 KafkaJS 的领导选举

Question

情况

我正在使用kafkajs写入一些动态生成的 kafka 主题。

我发现在注册我的制作人后立即写入这些主题通常会导致错误：There is no leader for this topic-partition as we are in the middle of a leadership election。

完整的错误是：

{"level":"ERROR","timestamp":"2020-08-24T17:48:40.201Z","logger":"kafkajs","message":"[Connection] Response Metadata(key: 3, version: 5)","broker":"localhost:9092","clientId":"tv-kitchen","error":"There is no leader for this topic-partition as we are in the middle of a leadership election","correlationId":1,"size":146}

代码

这是导致问题的代码：

{"level":"ERROR","timestamp":"2020-08-24T17:48:40.201Z","logger":"kafkajs","message":"[Connection] Response Metadata(key: 3, version: 5)","broker":"localhost:9092","clientId":"tv-kitchen","error":"There is no leader for this topic-partition as we are in the middle of a leadership election","correlationId":1,"size":146}

问题

两个问题：

1. 连接到生产者（或发送）时，我应该做些什么特别的事情，以确保逻辑阻塞，直到生产者真正准备好将数据发送到 kafka 主题？
2. 在向生产者发送数据时，我应该做些什么特别的事情以确保消息不会被丢弃？

Answer 1

解决方案

KafkajscreateTopics通过管理客户端提供了一种方法，该方法有一个可选waitForLeaders标志：

admin.createTopics({
  waitForLeaders: true,
  topics: [
    { topic: 'myRandomTopicString123' },
  ],
}

使用这个可以解决这个问题。

import kafka from 'myConfiguredKafkaJs'

const run = async () => {
  const producer = kafka.producer()
  const admin = kafka.admin()
  await admin.connect()
  await producer.connect()
  await admin.createTopics({
    waitForLeaders: true,
    topics: [
      { topic: 'myRandomTopicString123' },
    ],
  })
  producer.send({
    topic: 'myRandomTopicString',
    messages: [{
      value: 'yolo',
    }],
  })
}

run()

不幸的是，如果该主题已经存在，这将导致不同的错误，但这是一个单独的问题，我怀疑该错误比破坏更具信息性。

{"level":"ERROR","timestamp":"2020-08-24T18:19:48.465Z","logger":"kafkajs","message":"[Connection] Response CreateTopics(key: 19, version: 2)","broker":"localhost:9092","clientId":"tv-kitchen","error":"Topic with this name already exists","correlationId":2,"size":86}

编辑：上述设置确实需要正确配置您的 Kafka 实例。领导选举有可能永远无法解决，在这种情况下，KafkaJS 仍然会抱怨领导选举！

根据我的经验，这是由于 kafka 代理在没有从 Zookeeper 注销的情况下被停止的情况，这意味着 Zookeeper 正在等待不再存在的响应。