Kafka Zookeeper Leader election process failed in the Zookeeper ensemble.

Leader election failure can occur due to network issues, misconfiguration, or node failures.

Understanding Kafka Zookeeper

Apache Zookeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services. It is a critical component of Apache Kafka, where it is used to manage the Kafka brokers and maintain metadata about the Kafka cluster. Zookeeper ensures that the Kafka cluster is always in a consistent state and helps in leader election among Kafka brokers.

Identifying the Symptom

One of the common issues encountered in a Kafka Zookeeper setup is the LEADER_ELECTION_FAILURE. This issue manifests when the Zookeeper ensemble fails to elect a leader among the nodes. The symptom is typically observed as an inability for Kafka brokers to start properly or frequent leadership changes that disrupt the Kafka cluster's stability.

Details About the Issue

The LEADER_ELECTION_FAILURE error indicates that the Zookeeper ensemble is unable to successfully elect a leader. This can happen due to several reasons, such as network partitions, misconfigured Zookeeper nodes, or insufficient resources on the nodes. When the leader election process fails, it can lead to inconsistencies and unavailability of the Kafka cluster.

Common Causes

Network issues preventing nodes from communicating.
Misconfigured Zookeeper properties.
Node failures or insufficient resources.

Steps to Fix the Issue

Step 1: Verify Node Status

Ensure that all Zookeeper nodes are running and can communicate with each other. You can check the status of each node using the following command:

echo stat | nc localhost 2181

This command should return the status of the Zookeeper node. Ensure that at least one node is in the leader state and others are in the follower state.

Step 2: Check Network Connectivity

Verify that there are no network issues preventing nodes from communicating. Use tools like ping or telnet to ensure connectivity between nodes:

ping node2.example.comtelnet node3.example.com 2181

Step 3: Review Configuration

Check the zoo.cfg configuration file on each node to ensure that the settings are correct and consistent across the ensemble. Pay special attention to parameters like tickTime, initLimit, and syncLimit.

Step 4: Inspect Logs

Examine the Zookeeper logs for any errors or warnings that might indicate the cause of the leader election failure. Logs are typically located in the logs directory specified in the zoo.cfg file.

Additional Resources

For more information on configuring and troubleshooting Zookeeper, refer to the official Zookeeper Administrator's Guide. Additionally, the Kafka Documentation provides insights into how Kafka interacts with Zookeeper.

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MORE ISSUES

Kafka Zookeeper Configuration mismatch detected between Zookeeper nodes.

Inconsistent configuration settings across Zookeeper nodes.

Kafka Zookeeper An invalid event type was encountered in Zookeeper.

The application is not handling all possible event types emitted by Zookeeper.

Kafka Zookeeper SERVER_OVERLOADED

The Zookeeper server is overloaded with requests.

Kafka Zookeeper Inconsistent metadata detected in Zookeeper.

Configuration errors or unsynchronized nodes.

Kafka Zookeeper An exception occurred while processing a watcher event.

The watcher implementation may have errors or may not handle all cases.

Kafka Zookeeper Client disconnected from the Zookeeper server unexpectedly.

Network instability or client misconfiguration.

Kafka Zookeeper Failed to create a node in Zookeeper.

Ensure the parent node exists and check for permission issues.

Kafka Zookeeper An unexpected exception occurred in Zookeeper.

An unexpected exception can be caused by misconfigurations, network issues, or resource limitations.

Kafka Zookeeper CLIENT_TIMEOUT

The client timed out waiting for a response from Zookeeper.

Kafka Zookeeper The Zookeeper client is in an invalid state.

The Zookeeper client is in an invalid state.

Kafka Zookeeper DATA_TOO_LARGE error encountered when trying to write data to a Zookeeper node.

The data for a node exceeds the maximum allowed size.

Kafka Zookeeper SASL authentication failed for a Zookeeper client.

SASL configuration and credentials might be incorrect.

Kafka Zookeeper Failed to delete a node in Zookeeper.

The node is being accessed or has children nodes.

Kafka Zookeeper Zookeeper nodes are isolated and unable to communicate with each other.

A network partition has occurred, isolating Zookeeper nodes.

Kafka Zookeeper INVALID_CONFIG

Invalid configuration settings for Zookeeper.

Kafka Zookeeper CLIENT_CLOSED

The Zookeeper client was closed unexpectedly.

Kafka Zookeeper An unsupported operation was attempted on Zookeeper.

The operation is not supported by the current Zookeeper version.

Kafka Zookeeper Corruption detected in Zookeeper transaction logs.

Kafka Zookeeper Zookeeper Atomic Broadcast protocol error encountered.

Network issues or misconfiguration among Zookeeper nodes.

Kafka Zookeeper Zookeeper server is in read-only mode.

Zookeeper server is in read-only mode due to inability to achieve quorum.

Kafka Zookeeper Leader election process failed in the Zookeeper ensemble.

Leader election failure can occur due to network issues, misconfiguration, or node failures.

Kafka Zookeeper Failed to create or load a snapshot in Zookeeper.

Disk space issues or permission problems in the snapshot directory.

Kafka Zookeeper UNRESPONSIVE_FOLLOWER

A follower node is not responding in the Zookeeper ensemble.

Kafka Zookeeper JUTE_MAXBUFFER_EXCEEDED

The request exceeds the maximum buffer size.

Kafka Zookeeper WATCH_LIMIT_EXCEEDED error encountered in Kafka Zookeeper.

The client has exceeded the limit for registered watchers.

Kafka Zookeeper SERVER_SHUTDOWN

The Zookeeper server is shutting down.

Kafka Zookeeper INVALID_SESSION error encountered when interacting with Kafka Zookeeper.

The session ID is invalid or has been closed.

Kafka Zookeeper ACL_NOT_FOUND

The specified ACL was not found for the node.

Kafka Zookeeper An invalid callback was specified for a Zookeeper operation.

The callback function provided to a Zookeeper operation is not implemented correctly or is not registered properly.

Kafka Zookeeper WATCHER_REMOVED

A watcher was removed due to session expiration or disconnection.

Kafka Zookeeper Attempting to delete a node in Zookeeper results in a NODE_NOT_EMPTY error.

The node being deleted has child nodes, which prevents its deletion.

Kafka Zookeeper The client has exceeded the limit for ephemeral nodes.

The client is creating more ephemeral nodes than allowed by the Zookeeper configuration.

Kafka Zookeeper DISK_FULL error encountered in Kafka Zookeeper.

The disk used by Zookeeper is full.

Kafka Zookeeper INVALID_PATH error encountered when trying to access or create a Zookeeper node.

An invalid path was specified for a Zookeeper node.

Kafka Zookeeper UNSUPPORTED_VERSION error encountered when connecting to Zookeeper.

The client is using an unsupported version of the Zookeeper protocol.

Kafka Zookeeper SYNC_FAILED error encountered during a sync operation.

A sync operation failed to complete due to network issues or misconfigurations.

Kafka Zookeeper TOO_MANY_CONNECTIONS

Too many client connections to Zookeeper.

Kafka Zookeeper CONNECTION_TIMEOUT

The connection to the Zookeeper server timed out.

Kafka Zookeeper Zookeeper server ran out of memory.

Zookeeper server ran out of memory due to insufficient memory allocation or inefficient memory usage.

Kafka Zookeeper QUORUM_LOSS

The Zookeeper ensemble has lost quorum.

Kafka Zookeeper LEADER_NOT_FOUND

The Zookeeper ensemble cannot determine the leader.

Kafka Zookeeper Zookeeper server is not serving requests.

Zookeeper server is not properly configured or running.

Kafka Zookeeper Data inconsistency detected across Zookeeper nodes.

Data inconsistency in Zookeeper can occur due to network partitions, node failures, or improper configuration.

Kafka Zookeeper A Zookeeper operation took too long to complete.

The operation may be experiencing performance issues or the timeout setting is too low.

Kafka Zookeeper SESSION_MOVED

The session has moved to a different server.

Kafka Zookeeper INVALID_ACL error encountered when accessing a Zookeeper node.

An invalid ACL was specified for a node.

Kafka Zookeeper NO_NODE error encountered when attempting an operation on a Zookeeper node.

An operation was attempted on a node that does not exist.

Kafka Zookeeper CONNECTION_LOSS

The client lost its connection to the Zookeeper server.

Kafka Zookeeper SESSION_EXPIRED

The client's session with Zookeeper has expired.

Kafka Zookeeper Authentication with Zookeeper failed.

Incorrect authentication credentials or misconfiguration.

Kafka Zookeeper Encountering NODE_EXISTS error when trying to create a node in Zookeeper.

An attempt was made to create a node that already exists.

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