Kafka Kraft Upgrade Bug: Configuration Error From Zookeeper

Nov 20, 2025 by Alex Johnson 60 views

Introduction

In this article, we will delve into a specific bug encountered during a Kafka upgrade with Kraft mode from Zookeeper. This issue was reported within the Netcracker qubership-kafka project and highlights a critical configuration error that can lead to upgrade failures and potential data loss. We will explore the details of the bug, the steps to reproduce it, the expected behavior, and the environmental context in which it occurred. Understanding this bug is crucial for anyone managing Kafka deployments, especially those considering migrating from Zookeeper to Kraft mode. Proper planning and adherence to migration guidelines are essential to ensure a smooth transition and prevent data corruption. This comprehensive guide aims to provide insights into the bug and offer guidance on how to avoid it, ensuring your Kafka upgrade process is seamless and secure. The main goal is to enhance your understanding of the intricacies involved in Kafka upgrades, particularly when transitioning to Kraft mode, and to equip you with the knowledge to troubleshoot and resolve similar issues effectively. By the end of this article, you should have a clear understanding of the bug, its implications, and the best practices for a successful Kafka upgrade. Throughout this discussion, we will emphasize the importance of following official documentation and migration guides to prevent such errors, ensuring the integrity and availability of your Kafka cluster.

Bug Description

The bug report highlights an issue encountered during a Kafka upgrade with Kraft mode while transitioning from Zookeeper. The core problem lies in a configuration error that prevents the upgrade process from completing successfully. The error message, as indicated in the provided code snippet, clearly states that upgrading Kafka with Zookeeper to Kraft without proper migration procedures will result in data loss. This warning underscores the critical nature of following the correct migration path when switching to Kraft mode. Kraft mode, which eliminates the dependency on Zookeeper, offers several advantages, including simplified architecture and improved performance. However, this transition requires careful planning and execution to avoid data inconsistencies and potential downtime. The reported error specifically arises from the kafka/templates/cr.yaml file, indicating a misconfiguration within the Kafka resource definitions. This misconfiguration triggers a failure during the upgrade process, preventing the deployment from reaching its intended state. The bug report provides a direct link to a pipeline run on GitHub Actions, allowing for a detailed examination of the error logs and configuration files. This level of transparency is invaluable for troubleshooting and identifying the root cause of the issue. The documentation link provided in the bug report further emphasizes the importance of consulting official guides and migration procedures. The Kraft migration documentation outlines the necessary steps and considerations for a smooth transition, including pre-migration checks, data migration strategies, and post-migration validation. Ignoring these guidelines can lead to the errors described in the bug report, highlighting the need for a thorough understanding of the migration process.

Error Log Analysis

The provided error log snippet offers valuable insights into the nature of the bug. The message "Error: UPGRADE FAILED: execution error at (kafka/templates/cr.yaml:183:7)" indicates that the upgrade process failed due to an issue within the cr.yaml template file. Specifically, the error occurred at line 183, suggesting a misconfiguration or an invalid parameter setting within the Kafka resource definitions. The subsequent error message, "Error: You cannot upgrade Kafka with ZooKeeper to Kraft without migration, all data will be lost," clearly explains the root cause of the failure. This message highlights the critical requirement of performing a proper migration when transitioning from Zookeeper to Kraft mode. Upgrading directly without migration can lead to irreversible data loss, as the data formats and storage mechanisms differ between the two modes. The error message also directs users to the corresponding release documentation for further information. This guidance is essential for understanding the recommended migration procedures and best practices. The documentation typically includes detailed steps for backing up data, migrating existing Kafka topics and configurations, and validating the migration process. By consulting the release documentation, users can gain a comprehensive understanding of the migration requirements and avoid common pitfalls. The error log analysis underscores the importance of adhering to the recommended migration path when switching to Kraft mode. Ignoring this requirement can lead to severe consequences, including data loss and service disruption. Therefore, it is crucial to carefully review the official documentation and migration guides before attempting an upgrade.

Documentation Review

The bug report explicitly mentions the importance of referring to the documentation available at https://github.com/Netcracker/qubership-kafka/blob/main/docs/public/kraft-migration.md. This documentation serves as a critical resource for understanding the proper procedures for migrating to Kraft mode. A thorough review of this documentation is essential for anyone planning to upgrade their Kafka deployment. The documentation likely outlines the specific steps required to migrate from Zookeeper to Kraft, including pre-migration checks, configuration changes, and post-migration validation. It may also address common issues and troubleshooting tips. The Kraft migration process typically involves several key steps. First, it is crucial to back up existing Kafka data to prevent data loss in case of unforeseen issues. This backup should include both topic data and Kafka configurations. Next, the documentation may guide users through the process of configuring the Kafka cluster for Kraft mode. This configuration may involve modifying server properties, updating listener configurations, and adjusting the controller quorum settings. The documentation may also provide guidance on how to migrate existing Kafka topics and partitions to the Kraft metadata storage. This process may involve using Kafka's built-in tools or third-party migration utilities. Finally, the documentation should outline the steps for validating the migration. This validation may include verifying data integrity, testing Kafka producer and consumer functionality, and monitoring cluster performance. By carefully following the steps outlined in the documentation, users can minimize the risk of encountering errors during the migration process. Ignoring the documentation can lead to misconfigurations and data loss, as highlighted in the bug report.

Reproduction Steps

The bug report outlines a straightforward method to reproduce the issue: running the Clean Install pipeline and upgrading to the latest version. This process involves deploying a fresh Kafka cluster and then attempting to upgrade it to the latest release. The steps to reproduce the bug can be summarized as follows:

Initiate a Clean Install pipeline for the Kafka deployment.
Attempt to upgrade the deployed Kafka cluster to the latest version.

By following these steps, users can replicate the configuration error and observe the same failure reported in the bug report. This reproducibility is crucial for debugging and resolving the issue effectively. The Clean Install pipeline typically involves deploying a Kafka cluster from scratch, using a predefined configuration. This configuration may include default settings for Zookeeper, Kafka brokers, and other related components. The upgrade process, on the other hand, involves updating the existing Kafka deployment to a newer version. This process may involve modifying Kafka binaries, updating configuration files, and restarting Kafka brokers. The bug report suggests that the upgrade process fails when transitioning from Zookeeper to Kraft mode without proper migration. This failure indicates a misconfiguration within the upgrade scripts or deployment templates. By reproducing the bug, developers and operators can gain a better understanding of the underlying cause and develop a fix. The reproduction process also allows for testing potential solutions and verifying that the fix resolves the issue without introducing new problems. Therefore, the ability to reproduce the bug is an essential step in the bug resolution process.

Expected Behavior

The expected behavior during a Kafka upgrade, especially when transitioning to Kraft mode, is a seamless and error-free process. A clear and concise description of what should happen during a successful upgrade is essential for understanding the deviation caused by the bug. Ideally, the upgrade should proceed without any interruptions or failures, ensuring that the Kafka cluster remains available and operational throughout the process. This includes maintaining data integrity and minimizing downtime. When upgrading to Kraft mode, the expected behavior involves a controlled migration of metadata from Zookeeper to the Kraft quorum. This migration should be performed according to the official documentation and migration guides, ensuring that all data is transferred correctly and consistently. The upgrade process should also include validation steps to verify the integrity of the migrated data and the functionality of the Kafka cluster in Kraft mode. These validation steps may involve checking topic metadata, verifying producer and consumer functionality, and monitoring cluster performance. If any issues are encountered during the upgrade, the system should provide clear and informative error messages, guiding users to the appropriate troubleshooting steps. The error messages should be specific enough to identify the root cause of the problem and suggest potential solutions. In the case of the reported bug, the expected behavior was not achieved. The upgrade failed due to a configuration error, highlighting the importance of following the correct migration procedures. By understanding the expected behavior, users can better identify and address deviations caused by bugs or misconfigurations.

Environment

The bug report includes a section for environment details, which is crucial for understanding the context in which the issue occurred. However, the provided information is incomplete, with the Application Version and K8S Version fields left blank. Specifying the environment in detail is essential for troubleshooting and resolving bugs effectively. The Application Version refers to the version of the Kafka deployment being used. This information is critical for identifying potential version-specific issues and determining whether the bug has been fixed in later releases. The K8S Version refers to the version of Kubernetes on which the Kafka cluster is deployed. Kubernetes version compatibility is an important factor when managing Kafka deployments, as certain features and configurations may vary across different Kubernetes versions. In addition to the Application Version and K8S Version, other environmental details may also be relevant, such as the operating system, the Kafka broker configuration, and any custom modifications made to the deployment. Providing this information can help developers and operators better understand the environment in which the bug occurred and identify potential conflicts or incompatibilities. In the absence of specific environment details, it is challenging to narrow down the root cause of the bug. Therefore, it is crucial to include comprehensive environment information when reporting bugs or seeking assistance with Kafka deployments. This information can significantly expedite the troubleshooting process and facilitate the resolution of the issue.

Additional Context

The "Additional context" section of a bug report is an opportunity to provide any further information that may be relevant to understanding and resolving the issue. This may include specific configuration details, custom scripts, or other observations that are not covered in the previous sections. Providing additional context can significantly aid in the troubleshooting process by offering valuable clues and insights. In the case of the reported bug, the additional context could include details about the specific configuration changes made during the upgrade attempt, any custom resources or operators used in the deployment, and any relevant logs or metrics. This information can help developers and operators better understand the circumstances surrounding the bug and identify potential contributing factors. For example, if custom scripts were used to automate the upgrade process, providing these scripts can help identify any errors or misconfigurations within the scripts themselves. Similarly, if custom resources or operators were used to manage the Kafka deployment, providing details about these resources can help identify any compatibility issues or configuration conflicts. Relevant logs and metrics can also provide valuable insights into the behavior of the Kafka cluster during the upgrade process. These logs may reveal error messages, warnings, or performance bottlenecks that are not immediately apparent from the bug report itself. By providing comprehensive additional context, users can significantly increase the likelihood of a successful bug resolution. This information can help developers and operators quickly identify the root cause of the issue and develop an effective fix.

Conclusion

The bug report discussed in this article highlights a critical issue encountered during a Kafka upgrade with Kraft mode from Zookeeper. The configuration error, which prevents a successful upgrade without proper migration, underscores the importance of adhering to official documentation and migration guides. By understanding the bug, its reproduction steps, and the expected behavior, users can better prepare for Kafka upgrades and avoid potential data loss. The incomplete environment details in the report emphasize the need for comprehensive information when reporting bugs. Providing detailed environment information, along with additional context, significantly aids in the troubleshooting process. In conclusion, successful Kafka upgrades, especially when transitioning to Kraft mode, require careful planning, adherence to best practices, and a thorough understanding of the migration process. For further reading on Kafka migrations and best practices, consider visiting the official Apache Kafka documentation at https://kafka.apache.org/documentation/.