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Accelerate IIDR Kafka KCOPs Development: Introducing the KCOP Test Harness

By Majed Abed Moosa posted 2 days ago

  

What is a KCOP?

The CDC Replication Engine for Kafka uses Kafka Custom Operation Processors, or KCOPs, to transform data from a source system into a format that Kafka producers can handle. A KCOP allows developers to apply custom logic - for instance, filtering records, renaming fields, and reshaping message format.

To learn more about KCOPs, see our previous KCOPs blog.

What is the KCOP Test Harness?

The KCOP Test Harness is a standalone utility that makes it easy to develop and debug KCOPs without running a full CDC instance. Normally, testing a KCOP would mean setting up a subscription, between source and target engines and start flowing data - that can be a little time consuming if you are just trying to test a sample KCOP or your own custom KCOP. The KCOP Test Harness removes that complexity by simulating how CDC would calls your KCOP. You simply feed it input records, and it runs your KCOP logic as if those records were flowing through a live subscription! The tool then outputs the transformed Kafka messages, letting you quickly verify, troubleshoot and fine-tune your custom processing logic.

Why use the KCOP Test Harness?

The KCOP Test Harness is designed to make KCOP development more efficient and friendly. It provides a simple way to validate and refine your KCOP logic without needing to run a full replication flow.

Think of it as your go-to companion for KCOP debugging. If you ever encounter unexpected behavior at the KCOP level and only have a trace in your logs, the Test Harness can help a lot. Simply, take the failing records from your traces, configure your KCOP, and feed the records into the tool then you can reproduce and debug the issue locally! This makes troubleshooting much faster and clearer.

Conclusion

KCOPs offer a powerful way to customize how change data is transformed before being published to Kafka, giving developers full control over filtering, formatting, and more. While the CDC replication engine runs KCOPs in production, the KCOP Test Harness provides a lightweight, standalone environment for rapid development and debugging. Whether you're building a new KCOP or troubleshooting an existing one, the Test Harness streamlines the process, making KCOP development more efficient, flexible, and dev friendly.

For a deeper dive into it, check out our KCOPs blog!

Follow the links below for more information and a guide to set up:

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