Fix a memory leak in the failed instruction id cache.

[tvalentyn]

Sanitize the exception message stored for failed instructions to limit RAM growth.

Storing the original exception in the cache inadvertently captures stack frames and local variables, such as BundleProcessor objects, in the heap.

Drive by: decrease failed instruction ID cache size, and cap its growth by limiting exception message length.

fixes: #39406

internal reference: b/531440331

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a potential memory leak in the SDK worker's failed instruction cache. By capping the cache size and sanitizing the stored exception information—specifically by truncating excessively long error messages and tracebacks—the change ensures more stable memory usage during instruction failures.

Highlights

• Memory Optimization: Reduced the maximum number of failed instructions stored in the cache from 10,000 to 1,000 to limit memory growth.
• Exception Sanitization: Implemented truncation for exception messages and tracebacks stored in the failed instruction cache to prevent heap memory issues.
• Testing: Added unit tests to verify that the cache size is correctly capped and that long exception tracebacks are properly truncated.

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[gemini-code-assist]

Code Review

This pull request improves the memory management of the BundleProcessorCache by reducing the maximum number of stored failed instructions and implementing truncation for exception tracebacks. Unit tests were added to verify the cache size limits and traceback truncation logic. A valid review comment identified a potential compatibility issue with traceback.format_exception in Python versions prior to 3.10, providing a necessary fix to ensure backward compatibility.

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[gemini-code-assist]

In Python versions prior to 3.10, traceback.format_exception does not accept a single exception object as a positional argument and will raise a TypeError (missing value and tb arguments). Since Apache Beam supports Python 3.8 and 3.9, you should pass type(exception), exception, exception.__traceback__ to maintain backward compatibility.

      tb_str = "".join(
          traceback.format_exception(
              type(exception), exception, exception.__traceback__))

[tvalentyn]

R: @damccorm

[github-actions]

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