Troubleshooting Kafka can involve a wide range of issues, from configuration problems to performance tuning and ensuring proper communication between Kafka components. Below are common areas and steps to consider when troubleshooting Kafka:

1. Kafka Broker Issues

• Broker Not Starting:
  • Check the Kafka server logs (server.log) for errors. Common issues include incorrect configurations, such as zookeeper.connect, log.dirs, or insufficient permissions.
  • Ensure that the Kafka broker port (default is 9092) is not being used by another service.
• Broker Crashes or is Unresponsive:
  • Check for out-of-memory errors in the logs. Increase the heap size in KAFKA_HEAP_OPTS if necessary.
  • Monitor disk usage; Kafka requires sufficient disk space for logs.
  • Verify that Zookeeper is functioning properly, as Kafka relies on it for leader election and metadata storage.

2. Topic and Partition Issues

• Topic Not Created:
  • Ensure you have the correct permissions to create topics.
  • Verify that the replication factor and number of partitions are configured properly. If the replication factor exceeds the number of brokers, topic creation may fail.
• Under-replicated Partitions:
  • Check the broker logs for network or disk issues.
  • Ensure that all brokers in the cluster are up and running.
  • Monitor the network latency and bandwidth between brokers.

3. Producer and Consumer Issues

• Producer Cannot Connect:
  • Verify the broker address in the producer configuration.
  • Check for any network issues between the producer and the Kafka brokers.
  • Ensure the producer's acks setting is appropriately configured (e.g., acks=all for high durability).
• Messages Not Being Consumed:
  • Check the consumer group configuration and ensure it is subscribing to the correct topic.
  • Verify that the consumer offset is correctly managed; it might be that the consumer is reading from an offset where no new data is available.
  • Ensure that the consumer is connected to the correct Kafka brokers and that the consumer group is correctly set up.

4. Zookeeper Issues

• Zookeeper Connection Issues:
  • Ensure that the zookeeper.connect setting in Kafka's server.properties is correct.
  • Verify that Zookeeper is running and accessible from the Kafka brokers.
  • Check for any network partitioning or latency issues between Zookeeper and Kafka brokers.
• Leader Election Problems:
  • Check Zookeeper logs for issues related to leader election.
  • Ensure all Zookeeper nodes are correctly configured and communicating.

5. Performance Issues

• High Latency:
  • Monitor and tune the JVM settings, such as garbage collection (GC).
  • Check for disk I/O bottlenecks, and consider using faster disks or SSDs for Kafka logs.
  • Review the network throughput and latency between brokers, producers, and consumers.
• Slow Message Consumption:
  • Check the consumer lag using monitoring tools or Kafka metrics.
  • Increase the number of consumer threads or partitions to parallelize message consumption.
  • Tune the fetch size and consumer configuration parameters to optimize performance.

6. Data Integrity Issues

• Corrupted Data:
  • Run Kafka’s built-in data integrity tools, such as kafka-replica-verification and kafka-consumer-groups.
  • Check for any disk errors or hardware failures that might be affecting the data on Kafka brokers.

7. Logging and Monitoring

• Ensure that Kafka’s logging configuration is set to an appropriate level (DEBUG, INFO, WARN, etc.).