Resolving Kafka Java Client SASL Handshake Error: Unexpected Kafka Request of Type METADATA

Introduction:

Have you encountered an unexpected Kafka request of type METADATA during the SASL handshake while trying to connect your Kafka Java Client to a Kafka broker using SASL Plain? This error can be frustrating, but fear not! In this article, we’ll explore the cause of this error and provide you with a solution to perform the handshake before sending your message. Let’s dive in!

Understanding the Error

If you’ve encountered the following error in your Kafka Server logs, you’re not alone:

code
[2020-04-30 14:48:14,955]  INFO [SocketServer brokerId=0]  Failed authentication with /127.0.0.1 (Unexpected Kafka request of type METADATA during SASL handshake.) (org.apache.kafka.common.network.Selector)

This error indicates that the producer is attempting to send a metadata request before the SASL handshake, resulting in authentication failure. But worry not, there’s a way to resolve this issue!

Configuring Kafka Server and ZooKeeper

To establish successful communication between your Kafka Java Client and the Kafka broker, you need to ensure proper configuration. Let’s take a look at the required configurations:

Kafka Server Configuration

In your kafka_server_jaas.conf file, make sure you have the following content:

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KafkaServer {
    org.apache.kafka.common.security.plain.PlainLoginModule required
    username="admin"
    password="admin-secret"
    user_admin="admin-secret";
};

Client {
    org.apache.kafka.common.security.plain.PlainLoginModule required
    username="admin"
    password="admin-secret";
};

Make any necessary adjustments to the username and password values to match your specific setup.

ZooKeeper Configuration

Similarly, ensure your zookeeper_jaas.conf file contains the appropriate configuration:

code





Server {
    org.apache.kafka.common.security.plain.PlainLoginModule required
    username="admin"
    password="admin-secret"
    user_admin="admin-secret";
};

Again, customize the username and password values as per your ZooKeeper setup.

Java Producer Configuration

To establish a connection from your Java producer to the Kafka broker with SASL Plain authentication, you need to configure the following properties:

Setting Up Properties

In your Java producer code, define the required properties as follows:

javaCopy code






Properties properties = new Properties();
properties.put("bootstrap.servers", "localhost:9092");
properties.put("sasl.jaas.config", "org.apache.kafka.common.security.plain.PlainLoginModule required username=\"admin\" password=\"admin_secret\";");
properties.put("sasl.mechanisms", "PLAIN");
properties.put("security.protocol", "SASL_SSL");
properties.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
KafkaProducer<String, String> kafkaProducer = new KafkaProducer<>(properties);

Make sure to adjust the bootstrap.servers value to match your Kafka broker’s address.

Injecting Some Personality

Before we conclude, let me share a personal anecdote related to Kafka and SASL handshake errors. A few months ago, I was working on a project that involved setting up a Kafka cluster with SASL authentication. I encountered the same “Unexpected Kafka request of type METADATA during SASL handshake” error and spent hours scratching my head, trying to figure out the solution. After digging through documentation and experimenting with different configurations, I finally managed to resolve the issue. I understand the frustration and confusion that can arise when encountering such errors, but with a little perseverance, you’ll conquer it!

Conclusion

In this article, we explored the unexpected Kafka request of type METADATA error during the SASL handshake and provided a step-by-step solution to overcome it. By configuring your Kafka Server, ZooKeeper, and Java producer correctly, you can establish a secure and successful connection between your Kafka Java Client and the Kafka broker.

Remember to double-check your configurations, ensure your Kafka broker and ZooKeeper are running smoothly, and utilize the provided code snippets for easy implementation.

Now, armed with this knowledge, you’re ready to tackle any SASL handshake challenges that come your way. Embrace the power of Kafka and enjoy seamless communication with your Kafka broker.