Kafka：从 ZooKeeper 获取代理主机

Question

出于特殊原因，我需要同时使用 - ConsumerGroup（a.k.a。高级消费者）和 SimpleConsumer（a.k.a。低级消费者）来从卡夫卡读。对于 ConsumerGroup，我使用基于 ZooKeeper 的配置并且对此非常满意，但是 SimpleConsumer 需要实例化种子代理。

我不想保留两者的列表 - ZooKeeper 和代理主机。因此，我正在寻找一种方法来自动发现来自 ZooKeeper 的特定主题 的代理。

由于一些间接信息，我相信这些数据存储在以下路径之一的 ZooKeeper 中：

/brokers/topics/<topic>/partitions/<partition-id>/state
/brokers/ids/

但是，当我尝试从这些节点读取数据时，出现序列化错误（为此我使用 com.101tec.zkclient）：

org.I0Itec.zkclient.exception.ZkMarshallingError: java.io.StreamCorruptedException: invalid stream header: 7B226A6D at org.I0Itec.zkclient.serialize.SerializableSerializer.deserialize(SerializableSerializer.java:37) at org.I0Itec.zkclient.ZkClient.derializable(ZkClient.java:740) at org.I0Itec.zkclient.ZkClient.readData(ZkClient.java:773) at org.I0Itec.zkclient.ZkClient.readData(ZkClient.java:761) at org.I0Itec.zkclient.ZkClient.readData(ZkClient.java:750) at org.I0Itec.zkclient.ZkClient.readData(ZkClient.java:744) ... 64 elided Caused by: java.io.StreamCorruptedException: invalid stream header: 7B226A6D at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:804) at java.io.ObjectInputStream.(ObjectInputStream.java:299) at org.I0Itec.zkclient.serialize.TcclAwareObjectIputStream.(TcclAwareObjectIputStream.java:30) at org.I0Itec.zkclient.serialize.SerializableSerializer.deserialize(SerializableSerializer.java:31) ... 69 more

我可以毫无问题地写入和读取自定义 Java 对象（例如字符串），所以我相信这不是客户端的问题，而是编码的问题。因此，我想知道：

如果这是正确的方法，如何正确读取这些节点？
如果整个方法是错误的，什么是正确的？

Answer 1

这就是我的一位同事获取 Kafka 经纪人列表的方式。我认为当您想动态获取经纪人列表时，这是一种正确的方法。

下面是一个示例代码，展示了如何获取列表。

public class KafkaBrokerInfoFetcher {

    public static void main(String[] args) throws Exception {
        ZooKeeper zk = new ZooKeeper("localhost:2181", 10000, null);
        List<String> ids = zk.getChildren("/brokers/ids", false);
        for (String id : ids) {
            String brokerInfo = new String(zk.getData("/brokers/ids/" + id, false, null));
            System.out.println(id + ": " + brokerInfo);
        }
    }
}

运行由三个代理组成的集群上的代码导致

1: {"jmx_port":-1,"timestamp":"1428512949385","host":"192.168.0.11","version":1,"port":9093}
2: {"jmx_port":-1,"timestamp":"1428512955512","host":"192.168.0.11","version":1,"port":9094}
3: {"jmx_port":-1,"timestamp":"1428512961043","host":"192.168.0.11","version":1,"port":9095}

Answer 2

原来Kafka使用ZKStringSerializer来读写数据到znodes。因此，要修复错误，我只需将其添加为 ZkClient 构造函数中的最后一个参数：

val zkClient = new ZkClient(zkQuorum, Integer.MAX_VALUE, 10000, ZKStringSerializer)

使用它，我编写了几个有用的函数来发现经纪人 ID、他们的地址和其他东西：

import kafka.utils.Json
import kafka.utils.ZKStringSerializer
import kafka.utils.ZkUtils
import org.I0Itec.zkclient.ZkClient
import org.apache.kafka.common.KafkaException


def listBrokers(): List[Int] = {
  zkClient.getChildren("/brokers/ids").toList.map(_.toInt)
}

def listTopics(): List[String] = {
  zkClient.getChildren("/brokers/topics").toList
}

def listPartitions(topic: String): List[Int] = {
  val path = "/brokers/topics/" + topic + "/partitions"
  if (zkClient.exists(path)) {
    zkClient.getChildren(path).toList.map(_.toInt)
  } else {
    throw new KafkaException(s"Topic ${topic} doesn't exist")
  }
}

def getBrokerAddress(brokerId: Int): (String, Int) = {
  val path = s"/brokers/ids/${brokerId}"
  if (zkClient.exists(path)) {
    val brokerInfo = readZkData(path)
    (brokerInfo.get("host").get.asInstanceOf[String], brokerInfo.get("port").get.asInstanceOf[Int])
  } else {
    throw new KafkaException("Broker with ID ${brokerId} doesn't exist")
  }
}

def getLeaderAddress(topic: String, partitionId: Int): (String, Int) = {
  val path = s"/brokers/topics/${topic}/partitions/${partitionId}/state"
  if (zkClient.exists(path)) {
    val leaderStr = zkClient.readData[String](path)
    val leaderId = Json.parseFull(leaderStr).get.asInstanceOf[Map[String, Any]].get("leader").get.asInstanceOf[Int]
    getBrokerAddress(leaderId)
  } else {
    throw new KafkaException(s"Topic (${topic}) or partition (${partitionId}) doesn't exist")
  }
}

Answer 3

 public KafkaProducer(String zookeeperAddress, String topic) throws IOException,
        KeeperException, InterruptedException {

    this.zookeeperAddress = zookeeperAddress;
    this.topic = topic;

    ZooKeeper zk = new ZooKeeper(zookeeperAddress, 10000, null);
    List<String> brokerList = new ArrayList<String>();

    List<String> ids = zk.getChildren("/brokers/ids", false);
    for (String id : ids) {
        String brokerInfoString = new String(zk.getData("/brokers/ids/" + id, false, null));
        Broker broker = Broker.createBroker(Integer.valueOf(id), brokerInfoString);
        if (broker != null) {
            brokerList.add(broker.connectionString());
        }
    }

    props.put("serializer.class", KAFKA_STRING_ENCODER);
    props.put("metadata.broker.list", String.join(",", brokerList));
    producer = new Producer<String, String>(new ProducerConfig(props));
}

Answer 4

实际上，Kafka 中有 ZkUtils（至少 0.8.x 行），您可以使用它，但需要注意一个小问题：您需要 re-implement ZkStringSerializer 将字符串转换为 UTF-8 编码的字节数组。如果您想使用 Java8 的流式 API，您可以通过 scala.collection.JavaConversions 迭代 Scala 集合。这对我的案子有帮助。

Answer 5

要使用 shell 执行此操作：

zookeeper-shell myzookeeper.example.com:2181
ls /brokers/ids
  => [2, 1, 0]
get /brokers/ids/2
get /brokers/ids/1
get /brokers/ids/0

Kafka：从 ZooKeeper 获取代理主机

Kafka: Get broker host from ZooKeeper

apache-kafka

apache-zookeeper