KSQL-12554 | Ensure Deterministic UDF Loading by Avoiding Context ClassLoader Interference

[hrishabhg]

Description

In the current implementation, although the Thread.setContextClassLoader() method is not explicitly used, there is a possibility that the context class loader could be altered elsewhere, which was affecting the integration tests. This can lead to non-deterministic behavior in the loading of user-defined functions (UDFs) and cause unpredictable test results.

To address this issue, we ensure that the correct class loader is used explicitly for UDF loading without relying on the thread's context class loader. This change prevents unintended interference and guarantees that UDFs are loaded consistently, improving the stability and reliability of the integration tests.

The fix involves using ClassGraph.overrideClassLoaders(loader) to explicitly set the class loader for classpath scanning, thus avoiding any potential conflicts caused by changes to the thread's context class loader.

Testing done

• Unit/Integration Tests
• Manual Testing (Local Ksql-Server Setup)
  - All paths leading to UserFunctionLoader
  - All paths leading to UserFunctionLoader.loadClass
  - CustomUDF loading through a custom path

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")
• Do these changes have compatibility implications for rollback? If so, ensure that the ksql command version is bumped.

[confluent-cla-assistant]

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[VedarthConfluent]

Classgraph issue fix lgtm. cp build pr job can be fixed separately