How to Troubleshoot the Kafka DisconnectException Error During Fetch Requests?

What is the cause of the DisconnectException error when sending a fetch request to Kafka?

The DisconnectException error encountered during a fetch request to Kafka, specifically with messages like `sessionId=INVALID, epoch=INITIAL`, typically indicates a communication issue between the Kafka client and the Kafka broker. This can happen due to various reasons such as broker unavailability, misconfiguration, or client session issues.

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

// Ensure the session timeout is adequately set
props.put("session.timeout.ms", "30000");

KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);

Causes

• Kafka broker is down or unreachable
• Misconfigured client properties
• Network errors between the client and the broker
• Client session timeout issues
• Improper handling of authentication and authorization

Solutions

• Ensure the Kafka broker is running and reachable from the client machine.
• Check and correct any misconfiguration in the Kafka producer or consumer properties, such as `bootstrap.servers`, `security.protocol`, and `sasl.mechanism`.
• Investigate network issues that could be causing timeouts or packet loss between the client and the broker.
• Adjust the `session.timeout.ms` and `request.timeout.ms` configuration parameters to appropriate values for your environment.
• If using authentication, ensure the correct credentials and permissions are set.

Mistake: Using an outdated Kafka client version that is incompatible with the broker.

Solution: Upgrade to the latest Kafka client that matches the broker version.

Mistake: Not properly handling exceptions and retry logic in the Kafka client implementation.

Solution: Implement error handling and retry for Kafka requests to manage transient issues.

Mistake: Ignoring logs from both client and server to diagnose issues.

Solution: Regularly review logs from both the Kafka client and server for detailed error messages.