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's architecture, ensuring the coordination and management of Kafka brokers.
In the context of Kafka Zookeeper, you might encounter the WATCHER_REMOVED
issue. This symptom manifests when a watcher, which is a mechanism to get notifications of changes to Zookeeper nodes, is unexpectedly removed. This can lead to missed updates and inconsistencies in your Kafka cluster's state.
Typically, you will notice that certain updates or changes in the Zookeeper nodes are not being reflected in your application or Kafka cluster. This can lead to stale data being processed or incorrect configurations being applied.
The WATCHER_REMOVED
issue occurs when a watcher is removed due to session expiration or disconnection. Zookeeper sessions can expire if the client fails to send heartbeats within the session timeout period, often due to network issues or server overloads.
The primary cause of this issue is session expiration or disconnection. When a Zookeeper session expires, all associated watchers are removed. This can happen due to prolonged network partitions, high latency, or server resource constraints.
To resolve the WATCHER_REMOVED
issue, follow these steps:
Ensure that there is stable network connectivity between your Kafka clients and Zookeeper servers. Use tools like ping
or traceroute
to diagnose network issues.
Monitor your Zookeeper sessions to ensure they are not expiring prematurely. You can use the Zookeeper CLI to check session details and expiration times.
If a session has expired, you need to re-establish it. This involves reconnecting to the Zookeeper server and re-registering any necessary watchers. Ensure your application logic handles reconnections gracefully.
If session expirations are frequent, consider increasing the session timeout value. This can be configured in your Zookeeper client settings. However, be cautious as setting it too high can delay the detection of actual failures.
By understanding the WATCHER_REMOVED
issue and implementing the steps outlined above, you can ensure that your Kafka Zookeeper setup remains robust and reliable. For more detailed information, refer to the Zookeeper Programmer's Guide.
Let Dr. Droid create custom investigation plans for your infrastructure.
Book Demo