Brief Explanation
The "Kafka Leader not available" error in Logstash occurs when the Logstash Kafka input or output plugin cannot connect to the leader broker for a particular Kafka topic partition. This error indicates that Logstash is unable to read from or write to the Kafka cluster due to leadership issues.
Common Causes
- Kafka broker(s) are down or unreachable
- Network connectivity issues between Logstash and Kafka cluster
- Misconfiguration of Kafka broker addresses in Logstash
- Kafka cluster undergoing leadership election or rebalancing
- Insufficient replicas for the affected topic partitions
Troubleshooting and Resolution Steps
Verify Kafka cluster health:
- Check if all Kafka brokers are running
- Ensure there are no network issues between Logstash and Kafka
Review Logstash configuration:
- Confirm that the Kafka broker addresses are correct
- Verify that the topic and partition configurations are accurate
Check Kafka topic status:
- Use Kafka command-line tools to check topic and partition status
- Ensure that the topic has the correct number of replicas and in-sync replicas
Increase connection timeout and retry settings:
- Adjust
retry_backoff_ms
andreconnect_backoff_ms
in Logstash Kafka plugin configuration
- Adjust
Monitor Kafka logs for any leadership changes or errors
If the issue persists, consider restarting Kafka brokers or re-creating the affected topics
Best Practices
- Implement proper monitoring for both Logstash and Kafka clusters
- Use multiple Kafka brokers for high availability
- Configure appropriate replication factor for Kafka topics
- Regularly update Logstash and Kafka to the latest stable versions
- Implement circuit breakers or error handling in Logstash pipelines to manage Kafka connectivity issues
Frequently Asked Questions
Q: How long should I wait before considering the "Leader not available" error as persistent?
A: It's recommended to wait for at least 5-10 minutes, as temporary leadership changes or cluster rebalancing can cause short-lived errors. If the error persists beyond this time, further investigation is needed.
Q: Can this error occur even if all Kafka brokers are running?
A: Yes, it can occur if there are network issues, misconfiguration, or if the Kafka cluster is undergoing internal changes like leadership election.
Q: Will increasing the number of Kafka brokers help prevent this error?
A: While increasing the number of brokers can improve availability, it doesn't guarantee prevention of this error. Proper configuration and monitoring are equally important.
Q: How can I prevent data loss during such errors?
A: Implement proper error handling in Logstash, use persistent queues, and ensure your Kafka topics have an appropriate replication factor. Also, consider implementing a dead-letter queue for messages that fail to be processed.
Q: Is this error specific to certain versions of Logstash or Kafka?
A: This error can occur in various versions of Logstash and Kafka. However, staying updated with the latest stable versions can help mitigate known issues related to leadership and connectivity.