To check a Kafka topic

To check a Kafka topic, you can use the Kafka command-line tools or programmatically access the topic using a client library. Below are methods for checking Kafka topics.

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1. Using Kafka Command-Line Tools

Kafka includes a built-in script kafka-topics.sh to manage and check topics.

Check All Topics:

Run the following command to list all topics:

kafka-topics.sh --bootstrap-server <broker_host>:<broker_port> --list

Example:

kafka-topics.sh --bootstrap-server localhost:9092 --list

Describe a Specific Topic:

To get details about a specific topic, including partition count, replication factor, and partition leader:

kafka-topics.sh --bootstrap-server <broker_host>:<broker_port> --describe --topic <topic_name>

Example:

kafka-topics.sh --bootstrap-server localhost:9092 --describe --topic test-topic

Output example:

Topic: test-topic   PartitionCount: 3   ReplicationFactor: 2    Configs: segment.bytes=1073741824
    Topic: test-topic   Partition: 0    Leader: 1   Replicas: 1,2   Isr: 1,2
    Topic: test-topic   Partition: 1    Leader: 2   Replicas: 2,3   Isr: 2,3
    Topic: test-topic   Partition: 2    Leader: 3   Replicas: 3,1   Isr: 3,1

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2. Programmatic Approach

If you prefer to programmatically check a topic, you can use Kafka client libraries. Here’s an example in Node.js using kafkajs.

Install kafkajs:

npm install kafkajs

Example Code:

const { Kafka } = require('kafkajs');

const kafka = new Kafka({
  clientId: 'my-app',
  brokers: ['localhost:9092'], // Replace with your Kafka broker addresses
});

const checkTopic = async (topicName) => {
  const admin = kafka.admin();
  await admin.connect();

  // List all topics
  const topics = await admin.listTopics();
  console.log('Available topics:', topics);

  // Describe the specific topic
  if (topics.includes(topicName)) {
    const metadata = await admin.fetchTopicMetadata({ topics: [topicName] });
    console.log(`Metadata for topic "${topicName}":`, metadata);
  } else {
    console.log(`Topic "${topicName}" does not exist.`);
  }

  await admin.disconnect();
};

checkTopic('test-topic').catch(console.error);

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3. Using Kafka UI Tools

Several tools provide a GUI to check Kafka topics:

• Conduktor: A powerful Kafka GUI client for managing topics, consumers, and producers.
• AKHQ: A lightweight, open-source web-based tool for viewing and managing Kafka clusters.
• Kafka Manager: A web-based tool for administering Kafka topics and clusters.

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Key Points

• Kafka CLI is best for quick checks.
• Programmatic access is ideal for integration or automation.
• GUI tools offer a user-friendly way to explore and monitor topics.