Apache Kafka is a distributed event streaming platform used by thousands of companies for high-performance data pipelines, streaming analytics, data integration, and mission-critical applications. Zookeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services. It is a critical component of Kafka, ensuring that the Kafka brokers are aware of each other and maintaining the state of the Kafka cluster.
When working with Kafka Zookeeper, you might encounter an issue where a follower node becomes unresponsive. This can manifest as lagging in data replication, errors in client requests, or even a complete halt in the Kafka cluster's operations. The error message might not always be explicit, but symptoms include increased latency and failed requests.
The 'UNRESPONSIVE_FOLLOWER' issue occurs when one of the follower nodes in the Zookeeper ensemble stops responding. This can happen due to network issues, resource exhaustion, or hardware failures. Zookeeper operates as a quorum-based system, meaning that a majority of nodes must be operational for the system to function correctly. An unresponsive follower can disrupt this balance, leading to potential downtime or degraded performance.
To resolve the issue of an unresponsive follower in Kafka Zookeeper, follow these steps:
Ensure that the follower node can communicate with the leader and other nodes in the ensemble. Use tools like ping and telnet to check connectivity:
ping [follower-node-ip]
telnet [follower-node-ip] [zookeeper-port]
Log into the follower node and check CPU, memory, and disk usage. Use commands like top, free -m, and df -h to diagnose resource issues. If resources are exhausted, consider scaling up the node or redistributing the load.
Review the Zookeeper logs located in the /var/log/zookeeper directory (or your configured log directory) for any error messages or warnings that might indicate the cause of the unresponsiveness.
If the above steps do not resolve the issue, try restarting the Zookeeper service on the follower node:
sudo systemctl restart zookeeper
Or, if you are using a different service manager:
sudo service zookeeper restart
For more information on managing and troubleshooting Kafka Zookeeper, consider visiting the following resources:
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