Resolving SASL_SSL Configuration Issues: Accessing Topics in ksqlDB

Discover how to resolve access problems when reading topics in ksqlDB using SASL_SSL configuration settings.
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This video is based on the question https://stackoverflow.com/q/63712224/ asked by the user 'mjahr' ( https://stackoverflow.com/u/11701591/ ) and on the answer https://stackoverflow.com/a/63835369/ provided by the user 'mjahr' ( https://stackoverflow.com/u/11701591/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting Access to Topics in ksqlDB

When working with ksqlDB and its integration with Kafka, users sometimes encounter access issues that can be perplexing. If you've successfully implemented a secured Kafka server but find yourself unable to read topics while still accessing streams, you're not alone. Let's dive deeper into this issue and explore the solution effectively.

Understanding the Problem

The user is running ksqlDB on AWS EC2 instances with a secured Kafka server configured to use SASL_SSL and SASL mode PLAIN. Despite being able to list topics and successfully receive messages in push streams, the client faces a timeout when attempting to print topic data, receiving the message:
Timeout expired while fetching topic metadata.

Log entries indicate connection and authentication issues, leading to questions on how to leverage the existing setup for topic access.

Key Observations:

Successful connection to the KSQL server and REST API.

Ability to list topics without issues.

Successful push stream retrieval.

Failure during the print topic command with timeout.

These observations highlight that while some connections work as expected, others remain problematic, especially when accessing low-level topics directly.

Solution Breakdown

Identify the Configuration Gap

The core issue stems from the ksql client configuration. Users often overlook specific protocol requirements when attempting to connect to a secured Kafka server.

Required Configuration Adjustment

To resolve the access issue, you need to ensure that your ksql client configuration correctly specifies the communication security protocol. To do this, ensure that your ksql_cli.properties includes the following line:

[[See Video to Reveal this Text or Code Snippet]]

This configuration allows the ksql client to authenticate and communicate with the secured Kafka server effectively, ensuring that both client and server use the same security protocol.

Final Steps

Once you have updated the ksql_cli.properties file with the SASL_SSL security protocol configuration, retest the connection by performing the following:

Restart your ksqlDB client to ensure it picks up the new configuration.

Execute the print topic command again to see if the issue persists.

Conclusion

By making a simple yet critical adjustment to your client configuration, you can restore functionality and overcome the ability to access topics with ksqlDB. Remember that effective communication between components in a secured environment hinges on consistent security protocol settings across all configurations.

If you experience further difficulties, revisiting your configurations and ensuring they align with your expected security standards is vital. For more advanced troubleshooting, checking logs for detailed errors and ensuring that your SSL certificates are appropriately set up and accessible can save significant time.

In the world of data streaming and processing, even the smallest configuration gap can lead to significant challenges, but with diligence, these issues can be resolved swiftly. Happy querying!