How to get topic list from kafka server in Java

Question

I am using kafka 0.8 version and very much new to it.

I want to know the list of topics created in kafka server along with it's metadata. Is there any API available to find out this?

Basically, I need to write a Java consumer that should auto-discover any topic in kafka server.There is API to fetch TopicMetadata, but this needs name of topic as input parameters.I need information for all topics present in server.

Answer 1

I think this is the best way:

ZkClient zkClient = new ZkClient("zkHost:zkPort");
List<String> topics = JavaConversions.asJavaList(ZkUtils.getAllTopics(zkClient));

Answer 2

Using Scala:

import java.util.{Properties}
import org.apache.kafka.clients.consumer.KafkaConsumer

object KafkaTest {
  def main(args: Array[String]): Unit = {

    val brokers = args(0)
    val props = new Properties();
    props.put("bootstrap.servers", brokers);
    props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
    props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

    val consumer = new KafkaConsumer[String, String](props);
    val topics = consumer.listTopics().keySet();

    println(topics)
  }
}

Answer 3

with Kafka 0.9.0

you can list the topics in the server with the provided consumer method listTopics();

eg.

Map<String, List<PartitionInfo> > topics;

Properties props = new Properties();
props.put("bootstrap.servers", "1.2.3.4:9092");
props.put("group.id", "test-consumer-group");
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);
topics = consumer.listTopics();
consumer.close();

Answer 4

You can use zookeeper API to get the list of brokers as mentioned below:

    ZooKeeper zk = new ZooKeeper("zookeeperhost, 10000, null);
    List<String> ids = zk.getChildren("/brokers/ids", false);
    List<Map> brokerList = new ArrayList<>();
    ObjectMapper objectMapper = new ObjectMapper();

    for (String id : ids) {
        Map map = objectMapper.readValue(zk.getData("/brokers/ids/" + id, false, null), Map.class);
        brokerList.add(map);
    }

Use this broker list to get all the topic using the following link

https://cwiki.apache.org/confluence/display/KAFKA/Finding+Topic+and+Partition+Leader

Answer 5

If you want to pull broker or other-kafka information from Zookeeper then kafka.utils.ZkUtils provides a nice interface. Here is the code I have to list all zookeeper brokers (there are a ton of other methods there):

List<Broker> listBrokers() {

        final ZkConnection zkConnection = new ZkConnection(connectionString);
        final int sessionTimeoutMs = 10 * 1000;
        final int connectionTimeoutMs = 20 * 1000;
        final ZkClient zkClient = new ZkClient(connectionString,
                                               sessionTimeoutMs,
                                               connectionTimeoutMs,
                                               ZKStringSerializer$.MODULE$);

        final ZkUtils zkUtils = new ZkUtils(zkClient, zkConnection, false);

        scala.collection.JavaConversions.seqAsJavaList(zkUtils.getAllBrokersInCluster());
}

Answer 6

A good place to start would be the sample shell scripts shipped with Kafka. In the /bin directory of the distribution there's some shell scripts you can use, one of which is ./kafka-topic-list.sh If you run that without specifying a topic, it will return all topics with their metadata. See: https://github.com/apache/kafka/blob/0.8/bin/kafka-list-topic.sh

That shell script in turn runs: https://github.com/apache/kafka/blob/0.8/core/src/main/scala/kafka/admin/ListTopicCommand.scala

The above are both references to the 0.8 Kafka version, so if you're using a different version (even a point difference), be sure to use the appropriate branch/tag on github